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d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.5 Charging correlation principles for IM CN subsystems | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.5.1 Overview | This subclause describes charging correlation principles to aid with the readability of charging related procedures in clause 5. See 3GPP TS 32.240 [16] and 3GPP TS 32.260 [17] for further information on charging.
The IM CN subsystem generates and retrieves the following charging correlation information for later use with offline and online charging:
1. IM CN subsystem Charging Identifier (ICID);
2. Access network charging information;
3. Inter Operator Identifier (IOI);
4. Charging function addresses:
a. Charging Data Function (CDF);
b. Online Charging Function (OCF);
5. IM CN subsystem Functional Entity Identifier.
How to use and where to generate the parameters in IM CN subsystems are described further in the subclauses that follow. The charging correlation information is encoded in the P-Charging-Vector header field as defined in subclause 7.2A.5 and in RFC 7315 [52]. The P-Charging-Vector header field contains the following header field parameters: "icid-value", "icid-generated-at", "related-icid", "related-icid-generated-at", "access-network-charging-info", "orig-ioi", "term-ioi", "transit-ioi" and "fe-identifier".
The offline and online charging function addresses are encoded in the P-Charging-Function-Addresses as defined in RFC 7315 [52]. The P-Charging-Function-Addresses header field contains the following header field parameters: "ccf" for CDF and "ecf" for OCF.
NOTE: P-Charging-Function-Addresses parameters were defined using previous terminology. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.5.2 IM CN subsystem charging identifier (ICID) | The ICID is the session level data shared among the IM CN subsystem entities including ASs in both the calling and called IM CN subsystems. The ICID is used also for session unrelated messages (e.g. SUBSCRIBE request, NOTIFY request, MESSAGE request) for the correlation with CDRs generated among the IM CN subsystem entities.
The first IM CN subsystem entity involved in a SIP transaction will generate the ICID and include it in the "icid-value" header field parameter of the P-Charging-Vector header field in the SIP request.
For a dialog relating to a session, the generation of the ICID will be performed only on the initial request. This ICID will be used for the initial request and any response to the initial request, and all subsequent SIP messages ina P-Charging-Vector header field.
For all other transactions, generation of the ICID will be performed on each SIP request. This ICID will be used for the SIP request and any response to the SIP request in a P-Charging-Vector header field.
The "icid-value" header field parameter is inserted in the IM CN subsystem, as summarised in table 4-2A.
NOTE: This summary is also applicable for SIP messages which are not specified in clause 5, although each procedure for the P-Charging-Vector header field in clause 5 is described only for specific SIP message(s) (e.g. only for a 200 (OK) response).
Table 4-2A: Summary of ICID insertion in the IM CN subsystem
Inserted in
For initial or standalone SIP message
For subsequent SIP message
Any request
The first IM CN subsystem entity receiving the request inserts the "icid-value" header field parameter populated as specified in 3GPP TS 32.260 [17].
The first IM CN subsystem entity receiving the request inserts the "icid-value" header field parameter set to the value populated in the initial request for the dialog.
Any response to the request
The first IM CN subsystem entity receiving the response inserts the "icid-value" header field parameter set to the value populated in the initial request for the dialog or the standalone request.
The first IM CN subsystem entity receiving the response inserts the "icid-value" header field parameter set to the value populated in the initial request for the dialog.
See 3GPP TS 32.260 [17] for requirements on the format of ICID. The P-CSCF will generate an ICID for UE-originated calls. The I-CSCF will generate an ICID for UE-terminated calls if there is no ICID received in the initial request (e.g. the calling party network does not behave as an IM CN subsystem). The AS will generate an ICID when acting as an originating UA. The MGCF will generate an ICID for PSTN/PLMN originated calls. The MSC server will generate an ICID for ICS and SRVCC originated calls. Each entity that processes the SIP request will extract the ICID for possible later use in a CDR. The I-CSCF and S-CSCF are also allowed to generate a new ICID for UE-terminated calls received from another network.
There is also an ICID generated by the P-CSCF with a REGISTER request that is passed in a unique instance of P-Charging-Vector header field. The valid duration of the ICID is specified in 3GPP TS 32.260 [17].
The "icid-value" header field parameter is included in any request and response that includes the P-Charging-Vector header field. However, the P-Charging-Vector (and ICID) is not passed to the UE.
The ICID is also passed from the P-CSCF to the IP-CAN via PCRF. The interface supporting this operation is outside the scope of this document.
4.5.2A Related ICID
During the process of SRVCC access transfer the MSC server or the P-CSCF generates an ICID for the target access leg. For the purpose of charging correlation between the source access leg and the target access leg when the user is roaming the SCC AS and the ATCF includes the ICID used on the source access leg in the "related-icid" header field parameter of the P-Charging-Vector header field returned in 1xx and 2xx responses to the initial INVITE request.
During the process of dual radio access transfer the MSC server or the P-CSCF generates an ICID for the target access leg. For the purpose of charging correlation between the source access leg and the target access leg when the user is roaming the SCC AS includes the ICID used on the source access leg in the "related-icid" header field parameter of the P-Charging-Vector header field returned in 1xx and 2xx responses to the initial INVITE request. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.5.3 Access network charging information | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.5.3.1 General | The access network charging information are the media flow level data shared among the IM CN subsystem entities for one side of the session (either the calling or called side). GPRS charging information (GGSN identifier and PDP context information) is an example of access network charging information. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.5.3.2 Access network charging information | The IP-CAN provides the access network charging information to the IM CN subsystem. This information is used to correlate IP-CAN CDRs with IM CN subsystem CDRs, i.e. the access network charging information is used to correlate the bearer level with the session level.
The access network charging information is generated at the first opportunity after the resources are allocated at the IP-CAN. The access network charging information is passed from IP-CAN to P-CSCF via PCRF, over the Rx and Gx interfaces. Access network charging information will be updated with new information during the session as media flows are added or removed. The P-CSCF provides the access network charging information to the S-CSCF. The S-CSCF may also pass the information to an AS, which may be needed for online pre-pay applications. The access network charging information for the originating network is used only within that network, and similarly the access network charging information for the terminating network is used only within that network. Thus the access network charging information are not shared between the calling and called networks. The access network charging information is not passed towards the external ASs from its own network.
The access network charging information is populated in the P-Charging-Vector header field.
The access network charging information can be included in a P-Charging-Vector header field in dialog forming requests, mid-dialog requests, and responses. This is dependant on when updated information is avialable in the P-CSCF. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.5.4 Inter operator identifier (IOI) | The Inter Operator Identifier (IOI) is a globally unique identifier to share between sending and receiving networks, service providers or content providers.
The sending network populates the "orig-ioi" header field parameter of the P-Charging-Vector header field in a request and thereby identifies the operator network from which the request was sent. The "term-ioi" header field parameter is left out of the P-Charging-Vector header field in this request. The sending network retrieves the "term-ioi" header field parameter from the P-Charging-Vector header field in a response to the request, which identifies the operator network from which the response was sent.
The receiving network retrieves the "orig-ioi" header field parameter from the P-Charging-Vector header field in the request, which identifies the operator network from which the request was sent. The receiving network populates the "term-ioi" header field parameter of the P-Charging-Vector header field in the response to the request, which identifies the operator network from which the response was sent.
The "orig-ioi" and "term-ioi" header field parameters are inserted in the IM CN subsystem, as summarised in table 4-2B.
NOTE: This summary is also applicable for SIP messages which are not specified in clause 5, although each procedure for the P-Charging-Vector header field in clause 5 is described only for specific SIP message(s) (e.g. only for a 200 (OK) response).
Table 4-2B: Summary of IOI insertion in the IM CN subsystem
Inserted in
For initial, standalone or subsequent SIP message
Any request
The IM CN subsystem entity in the sending network:
1) removes any received "orig-ioi" header field parameter, if present;
2) inserts the "orig-ioi" header field parameter to a value that identifies the sending network of the request; and
3) does not insert the "term-ioi" header field parameter.
Any response to the request
The IM CN subsystem entity in the receiving network:
1) removes any received "orig-ioi" and "term-ioi" header field parameters, if present;
2) inserts the "orig-ioi" header field parameter set to the previously received value of "orig-ioi" header field parameter, if received in the request; and
3) inserts the "term-ioi" header field parameter to a value that identifies the receiving network from which the response is sent.
There are three types of IOI:
a) Type 1 IOI, between the visited network and the home network. This includes the following cases:
- between the P-CSCF (possibly in the visited network) and the S-CSCF in the home network. This is exchanged in REGISTER requests and responses, and in all session-related and session-unrelated requests and responses;
- between the SCC AS in the home network and the ATCF (possible in the visited network). This is exchanged in MESSAGE requests and responses;
NOTE: For applications where the primary relationship is home and visited network, request and responses to the request will normally contain a type 1 IOI value.
- between the MSC server (possibly in the visited network) and the S-CSCF in the home network. This is exchanged in REGISTER requests and responses, and in all session-related and session-unrelated requests and responses; and
- when using Roaming Architecture for Voice over IMS with Local Breakout and loopback routeing occurs, between the S-CSCF of the home network and the TRF of the visited network or between the BGCF of the home network and the TRF of the visited network. This is exchanged in all session-related requests and responses.
b) Type 2 IOI, between originating network and the terminating network. This includes the following cases:
- between the S-CSCF of the home originating network and the S-CSCF of the home terminating network or between the S-CSCF of the home originating network and the MGCF when a call/session is terminated at the PSTN/PLMN;
- between the MGCF and the S-CSCF of the home terminating network when a call/session is originated from the PSTN/PLMN or with a PSI AS when accessed across I-CSCF; and
- when using Roaming Architecture for Voice over IMS with Local Breakout and loopback routeing occurs, between the TRF of the visited network and the S-CSCF of the home terminating network.
This is exchanged in all session-related and session-unrelated requests and responses.
Additionally, for emergency transactions, a type 2 IOI is exchanged between the E-CSCF and the MGCF or IBCF where the request is routed to a PSAP. In scenarios where the E-CSCF receives emergency requests from an S-CSCF, a type 2 IOI is exchanged. This can also occur where the E-CSCF receives emergency requests from an IBCF.
c) Type 3 IOI, between the S-CSCF or I-CSCF of the home operator network and any AS. Type 3 IOI are also used between E-CSCF and LRF, between E-CSCF and EATF, and between transit function and AS. The type 3 IOI is exchanged in all session-related and session-unrelated requests and responses.
Each entity that processes the SIP request will extract the IOI for possible later use in a CDR. The valid duration of the IOI is specified in 3GPP TS 32.240 [16].
4.5.4A Transit inter operator identifier (Transit IOI)
The Transit Inter Operator Identifier (Transit IOI) is a globally unique identifier to share between sending, transit and receiving networks, service providers or content providers.
A network sending a request can retrieve the "transit-ioi" header field parameter value(s) from the P-Charging-Vector header field in the response to the sent request, which identify the operator network(s) which the response was transitting.
The transit network(s) populate(s) the "transit-ioi" header field parameter value(s) of the P-Charging-Vector header field in a request and thereby identify(ies) the operator network(s) which the request was transitting. The "transit-ioi" header field parameter is an indexed value that is incremented each time a value is added. When the index is calculated then "void" entries are taken into account.
The transit network(s) populate(s) the "transit-ioi" header field parameter value(s) of the P-Charging-Vector header field in the response to the request and thereby identify(ies) the operator network(s) which the response was transitting. The "transit-ioi" header field parameter is an indexed value that is incremented each time a value is added. When the index is calculated then "void" entries are taken into account.
A network receiving a request can retrieve the "transit-ioi" header field parameter value(s) from the P-Charging-Vector header field in the request, which identify the operator network(s) which the request was transitting.
EXAMPLE:
Transit-IOI in a request when arriving on the terminating side:
P-Charging-Vector: icid-value="AyretyU0dm+6O2IrT5tAFrbHLso=023551024"; orig-ioi=home1.net; transit-ioi="operatorA.1, void, operatorB.3"
Transit-IOI in the corresponding response when arriving on the originating side:
P-Charging-Vector: icid-value="AyretyU0dm+6O2IrT5tAFrbHLso=023551024"; orig-ioi=home1.net; term-ioi=home2.net; transit-ioi="operatorB.1, void, operatorA.3"
The Transit IOI is exchanged between functional entities, as summarised in table 4-3.
Table 4-3: Summary of Transit IOI exchange in the IM CN subsystem
Item
Entities adding Transt IOI
(NOTE 1)
Entities deleting Transit IOI
(NOTE 1)
1
additional routeing functions as defined in annex I or IBCF (NOTE 2) in the transit network located between the visited network and the home network
S-CSCF of the home network;
P-CSCF of the visited network; or
TRF of the visited originating network when using Roaming Architecture for Voice over IMS with Local Breakout and loopback routeing occurs
2
additional routeing functions as defined in annex I or IBCF (NOTE 2) in the transit network located between originating network and the terminating network
S-CSCF of the home terminating network;
S-CSCF of the home originating network;
MGCF when a call/session is terminated at the PSTN/PLMN; or
TRF of the visited originating network when using Roaming Architecture for Voice over IMS with Local Breakout and loopback routeing occurs
3
additional routeing functions as defined in annex I colocated with MGCF when a call/session was transitting the PSTN/PLMN
S-CSCF of the home terminating network
NOTE 1: Transit IOIs can also be exchanged with non 3GPP networks, e.g. IPX networks.
NOTE 2: In the transit network, the IBCF acting as an entry point adds the Transit IOI in requests and the IBCF acting as an exit point adds the Transit IOI in responses, as described in subclause 5.10.
Each entity that processes the SIP requests and responses may extract the Transit IOI for charging purposes, as described in 3GPP TS 32.260 [17]. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.5.5 Charging function addresses | Charging function addresses are distributed to each of the IM CN subsystem entities in the home network for one side of the session (either the calling or called side) and provide a common location for each entity to send charging information. Charging Data Function (CDF) addresses are used for offline billing. Online Charging Function (OCF) addresses are used for online billing.
There may be multiple addresses for CDF and OCF addresses populated into the P-Charging-Function-Addresses header field of the SIP request or response. The header field parameters are "ccf" and "ecf" for CDF and OCF, respectively. At least one instance of either "ccf" or "ecf" header field paramter is required. If "ccf" header field parameter is included for offline charging, then a secondary "ccf" header field paramter may be included by each network for redundancy purposes, but the first instance of "ccf" header field parameter is the primary address. If ecf address is included for online charging, then a secondary instance may also be included for redundancy.
The CDF and/or OCF addresses are retrieved from an Home Subscriber Server (HSS) via the Cx interface and passed by the S-CSCF to subsequent entities. The charging function addresses are passed from the S-CSCF to the IM CN subsystem entities in its home network, but are not passed to the visited network or the UE. When the P-CSCF is allocated in the visited network, then the charging function addresses are obtained by means outside the scope of this document. The AS receives the charging function addresses from the S-CSCF via the ISC interface. CDF and/or OCF addresses may be allocated as locally preconfigured addresses. The AS can also retrieve the charging function address from the HSS via Sh interface. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.5.6 Relayed charge parameters | Where there is a desire to pass charging information to an entity over an interface to which the charging information is not directly related, then the Relayed-Charge header field is used. This is used only in accordance with the capabilities specified in this document, which currently specify only the relay of a transit IOI to an associated AS. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.5.7 Loopback-indication parameter | When there is a desire to send the information that loopback has been applied to an entity, then the loopback-indication parameter is used. This parameter can e.g. be evaluated when processing the P-CSCF CDR and possibly the ATCF CDR to know whether or not to attempt to locate a correlated TRF CDR even for the non-loopback scenario when no such CDR exists. It is used only in accordance with the capabilities specified in this document. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.5.8 IM CN subsystem Functional Entity Identifier | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.5.8.1 General | Different rules for generating and processing of charging information apply. In order to inform the billing domain which IM CN subsystem functional entities have created charging information, the IM CN subsystem functional entities and ASs include an "fe-identifier" header field parameter as additional information in the P-Charging-Vector header field when generating charging information as specified in 3GPP TS 32.260 [17].
NOTE: Within the billing domain this information given within the "fe-identifier" header field in a final response allows the billing domain to compare the generated data records for specific IM CN subsystem functional entities with the recorded addresses/identifiers of the IM CN subsystem functionial entities themselves. Thus information can be compared and missing information can be identified. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.5.8.2 Tracking of IM CN subsystem functional entities generating charging information | Each IM CN subsystem functional entity that generates charging events, includes its own address or specific IM CN subsystem functional entity identifier within the "fe-addr" element of the "fe-identifier" header field parameter of the P-Charging-Vector header field into the initial SIP request to be sent from own domain.
The last element of the operator domain stores the "fe-identifier" header field parameter in the P-Charging-Vector header field and removes the "fe-identifier" header field parameter from the P-Charging-Vector header field.
When receiving the final SIP response sent back to its own domain, the last element of the operator domain deletes, if received, the "fe-identifier" header field parameter from the P-Charging-Vector header field, adds the stored "fe-identifier" and adds its own "fe-addr" to the "fe-identifier". |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.5.8.3 Tracking of applications generating charging information | Each application for which the hosting AS is generating charging events, includes the address or specific identifier of the AS within the "as-addr" element and the application identifier within the "ap-id" element of the "fe-identifier" header field parameter of the P-Charging-Vector header field into the initial SIP request to be sent.
The final SIP response sent back by the last element of the operator domain supporting the "fe-identifier" header field contains the list of addresses and application identifiers received within the initial SIP request. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.6 Support of local service numbers | For the IM CN subsystem, the support of local service numbers is provided by an AS in the subscriber's home network as described in subclause 5.7.1.7. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.7 Emergency service | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.7.1 Introduction | The need for support of emergency calls in the IM CN subsystem is determined by national regulatory requirements. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.7.2 Emergency calls generated by a UE | If the UE cannot detect the emergency call attempt, the UE initiates the request as per normal procedures as described in subclause 5.1.2A. Depending on network policies, for a non-roaming UE or for a roaming UE where the P-CSCF is in the same network where the UE is roaming an emergency call attempt can succeed even if the UE did not detect that an emergency session is being requested, otherwise the network rejects the request indicating to the UE that the attempt was for an emergency service.
The UE procedures for UE detectable emergency calls are defined in subclause 5.1.6.
The P-CSCF, S-CSCF, IBCF, and E-CSCF procedures for emergency service are described in subclause 5.2.10, 5.4.8, 5.10.3.2 and 5.11, respectively.
Access dependent aspects of emergency service (e.g. whether the access technology defines emergency bearers, emergency registration support and location provision) are defined in the access technology specific annexes for each access technology.
There are a number of variants within these procedures and which variant gets used depends on a number of issues. These conditions are defined more specifically in 3GPP TS 23.167 [4B] and, where appropriate, in the access technology specific annex, but are summarised as follows:
a) if the UE knows that it is in its own home network, then an existing registration is permitted to be used for signalling the emergency call, except where item c) applies. The access technology specific annexes define the mechanism by which home network determination is made;
b) if emergency calls are permitted without security credentials (or additionally where the authentication is not possible or has failed), then the emergency call is made directly without use of any security association created by a registration, and therefore without the registration; and
c) where the access technology defines emergency bearers for the support of emergency calls, a new emergency registration is required so that these emergency bearers can be used for both signalling and media, unless an existing emergency registration exists on those emergency bearers. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.7.3 Emergency calls generated by an AS | In certain circumstances an AS can identify that a request is an emergency call. This may relate to a request received from a UE (or subscription-based business trunking), or may be a call generated by an AS on behalf of a UE as far as the IM CN subsystem operation is concerned. These applications are outside the scope of this document to define.
Procedures in support of an AS initiating emergency calls are provided in subclause 5.7.1.14. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.7.4 Emergency calls received from an enterprise network | An IBCF can also route emergency calls received from an enterprise network (peering-based business trunking) to an E-CSCF. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.7.5 Location in emergency calls | A number of mechanisms also exist for providing location in support of emergency calls, both for routeing to a PSAP, and for use by the PSAP itself, in the IM CN subsystem:
a) by the inclusion by the UE of the Geolocation header field containing a location by reference or by value (see RFC 6442 [89]);
b) by the inclusion by the UE of a P-Access-Network-Info header field, which contains a cell identifier or location identitifier, which is subsequently mapped, potentially by the recipient, into a real location;
c) by the inclusion by the P-CSCF of a P-Access-Network-Info header field based on information supplied by either the PCRF or the NASS, and which contains a cell identifier or location identitifier, which is subsequently mapped, potentially by the recipient, into a real location;
d) by the allocation of a location reference that relates to the call by the LRF. Location is then supplied to the recipient over the Le interface (see 3GPP TS 23.167 [4B] for a definition of the Le interface) along with other call information. The LRF can obtain the location from entities outside the IM CN subsystem, e.g. by the e2 interface from the NASS (see ETSI TS 283 035 [98] or from the Gateway Mobile Location Centre (GMLC); and
e) by the inclusion by the S-CSCF of a P-Access-Network-Info header field based on information supplied by HSS, and which contains a location identitifier, which is subsequently mapped, potentially by the recipient, into a real location.
Mechanisms also exist for providing emergency-related information to a PSAP, in requests subsequent to routeing an initial request to a PSAP, in the IM CN subsystem:
a) by the inclusion by the UE of the Geolocation header field containing a location by reference or by value (see RFC 6442 [89]);
b) by the inclusion by the UE of a P-Access-Network-Info header field, which contains a cell identifier or location identitifier, which is subsequently mapped, potentially by the recipient, into a real location;
c) by the inclusion by the P-CSCF of a P-Access-Network-Info header field based on information supplied by either the PCRF or the NASS, and which contains a cell identifier or location identitifier, which is subsequently mapped, potentially by the recipient, into a real location;
d) by the inclusion by the UE of the emergency-related information as specified in subclause 5.1.6.10;
e) by the inclusion by the S-CSCF of a P-Access-Network-Info header field based on information supplied by HSS, and which contains a location identitifier, which is subsequently mapped, potentially by the recipient, into a real location; and
f) by LRF requesting the location from the UE via E-CSCF as specified in subclause 5.12.3.2, subclause 5.11.4.3, subclause 5.11.4.4, subclause 5.11.5 and subclause 5.1.6.12.
The E-CSCF routes such a subsequent request to the PSAP using normal SIP procedures.
NOTE 1: Mechanisms independent from SIP for providing the emergency related information to a PSAP after session setup exist and are not listed. The use of such mechanisms is not precluded.
Which means of providing location is used depends on local regulatory and operator requirements. One or more mechanisms can be used. Location can be subject to privacy constraints.
NOTE 2: A similar variety of mechanisms also exists for normal calls, where location can be made use of by the recipient or by an intermediate AS, again subject to privacy constraints. The LRF is not involved in a normal call, but an AS can obtain location from the e2 interface from the NASS (see ETSI TS 283 035 [98] or from the Gateway Mobile Location Centre (GMLC). |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.7.6 eCall type of emergency service | A PSAP supporting eCall over IMS supports:
- receipt of the minimum set of emergency related data (MSD) in an INVITE or INFO request;
- the EmergencyCallData.eCall.MSD Info-Package and the ability to request an updated MSD by including an "application/EmergencyCallData.Control+xml" MIME body part containing a "request" element with an "action" attribute set to "send-data" and a "datatype" attribute set to "eCall.MSD" in an INFO request as defined in RFC 8147 [244];
- sending of an acknowledgement for an MSD received in an INVITE request by including, in the final response to the INVITE request, an "application/EmergencyCallData.Control+xml" MIME body part with an "ack" element containing a "received" attribute set to "true" or "false" and a "ref" attribute set to the Content-ID of the MIME body part containing the MSD sent by the UE, as defined in RFC 8147 [244];
- receipt of the MSD using audio media stream encoded as described in 3GPP TS 26.267 [9C] if requesting and providing MSD is required in:
1) an IMS emergency call of the automatically or manually initiated eCall type of emergency service, which was established in PS and later on handed over to CS;
2) PSAP callback, which was established in PS and later on handed over to CS;
3) PSAP callback, which was accepted by the UE in CS; or
4) IMS non-emergency call of the test eCall type, which was established in PS and later on handed over to CS;
- the ability to request an updated MSD using audio media stream encoded as described in 3GPP TS 26.267 [9C] if requesting and providing MSD is required in:
1) an IMS emergency call of the automatically or manually initiated eCall type of emergency service, which was established in PS and later on handed over to CS;
2) PSAP callback, which was established in PS and later on handed over to CS;
3) PSAP callback, which was accepted by the UE in CS; or
4) IMS non-emergency call of the test eCall type, which was established in PS and later on handed over to CS; and
- the ability to request an updated MSD using audio media stream encoded as described in 3GPP TS 26.267 [9C], if the remote UA modifies an IMS emergency call of the eCall type of emergency service and stops supporting the EmergencyCallData.eCall.MSD Info-Package defined in RFC 8147 [244].
NOTE 1: The remote UA modifies an IMS emergency call of the eCall type of emergency service and stops supporting the EmergencyCallData.eCall.MSD Info-Package defined in RFC 8147 [244] when SRVCC access transfer takes place.
NOTE 2: Receipt of the MSD using audio media stream encoded as described in 3GPP TS 26.267 [9C] is optional for a PSAP that supports eCall over IMS according to CEN EN 17184:2024 [300]. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.8 Tracing of signalling | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.8.1 General | IM CN subsystem entities can log SIP signalling, for debugging or tracing purposes, as described in 3GPP TS 32.422 [17A]. Debugging of SIP signalling is configured using the 3GPP IMS service level tracing management object (MO), specified in 3GPP TS 24.323 [8K]. This management object can provide configuration data to a UE or an S-CSCF, including in a visited network. Logging always begins with the initial request that creates a dialog and ends when a pre-configured stop trigger occurs or the dialog ends, whichever occurs first, as described in RFC 8497 [140] and configured in the trace management object defined in 3GPP TS 24.323 [8K]. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.8.2 Trace depth | The depth parameter in trace control and configuration indicates which SIP requests and responses are logged. If the trace depth is "maximum" then all requests and responses within a dialog or standalone transaction are logged. If the trace depth is "minimum" then all requests and responses except for non-reliable 1xx responses (including 100 (Trying) responses) and the ACK request are logged. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.9 Overlap signalling | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.9.1 General | This subclause explains the overlap signalling impacts on the core entities of the IM CN subsystem.
The support of overlap signalling, and each of the overlap signalling method, within the IM CN subsystem, are optional and is dependent on the network policy.
Only one overlap signalling method shall be used within one IM CN subsystem.
NOTE: Interworking between the overlap signalling methods is not specified in this release. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.9.2 Overlap signalling methods | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.9.2.1 In-dialog method | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.9.2.1.1 General | The in-dialog method uses INFO requests or INVITE requests in order to transport additional digits. Before an early dialog has been established, upon reception of a 404 (Not Found) or 484 (Address Incomplete) response to an earlier INVITE request, new INVITE requests will be sent to transfer additional digits (as specified in 3GPP TS 29.163 [11B]). Once an entity establishes an early dialog, by sending a provisional response to a INVITE request, INFO requests will be sent to carry additional digits on the early dialog.
The message body, and associated header values, which is used to carry additional digits in INFO requests is defined in 3GPP TS 29.163 [11B]. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.9.2.2 Multiple-INVITE method | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.9.2.2.1 General | The multiple-INVITE method uses INVITE requests with the same Call ID and From header in order to transport digits (as specified in 3GPP TS 29.163 [11B]). |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.9.3 Routeing impacts | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.9.3.1 General | If overlap dialing is supported, the IM CN subsystem needs to be configured in such a manner that erroneous routeing of INVITE requests with incomplete numbers towards others entities than the corresponding INVITE requests with full numbers is avoided, for instance towards a default destination for unknown numbers such as a PSTN. Possibly impacted nodes include the S-CSCF for the UE-originated case, the transit routeing function, the I-CSCF, and application servers.
A misrouteing can be avoided by configuring the entity sending overlap signalling in such a manner that it will send the first INVITE request with a sufficient number of digits to find a suitable entry in the translation database. If ENUM is used, the ENUM database in a typical deployment contains sufficient information about the first digits, as required to identify the destination IP domain. Therefore, ENUM is able to handle incomplete numbers in such deployments. As another alternative, the routeing entity can reject calls with unknown numbers with a 404 (Not Found) response, using entries in the routeing database to identify calls towards the PSTN. The S-CSCF for the UE-originated case could also forward calls with unknown numbers to the BGCF, if the BGCF is configured to reject calls to unknown destinations with a 404 (Not Found) response. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.9.3.2 Deterministic routeing | If the multiple-INVITE method is used for overlap signalling, if an entity receives a INVITE request outside an existing dialog with the same Call ID and From header field as a previous INVITE request during a certain period of time, the entity shall route the new INVITE request to the same next hop as the previous INVITE request.
NOTE: INVITE requests with the same Call ID and From header fields received in sequence during a certain period of time belong to the same call. The routeing towards the same next hop could be achieved by an appropriately configured database or by the entity comparing the Call ID and From header fields of each INVITE request outside an existing dialog with Call IDs and "tag" From header field parameters of previous INVITE requests. If the entity compares the Call ID and From header field, it stores the information about received Call ID and From header fields at least for a time in the order of call setup times. If paths have been established at registration time, deterministic routeing will be automatic for entities on these paths. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.9.3.3 Digit collection | Entities performing routeing decicisions may require additional digits for a decision where to route an INVITE request. These entities may interact with a routeing database to reach this decision.
If no suitable entry in a database is found for the digits received in a INVITE request, an entity can reject the INVITE request with a 404 (Not Found) or 484 (Address Incomplete) response. This method of digit collection can be performed by a SIP proxy and is suitable both for the in-dialog and multiple-INVITE overlap signalling methods. Replying with a 404 (Not Found) response avoids the need to keep apart uncomplete and unknown numbers. The 484 (Address Incomplete) response requires the recognition of incomplete numbers.
NOTE: An HSS does not support the recognition of incomplete numbers. A routeing database being queried by ENUM also does not support the recognition of incomplete numbers.
As an alternative for the in-dialogue method, the digit collection function described in annex N.2 may be invoked. It shall be performed by an entity acting as a B2BUA. The digit collection function requires the ability to recognise incomplete number. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.10 Dialog correlation for IM CN subsystems | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.10.1 General | The Call-ID header field in combination with the tags in the From header field and in the To header field is the standard mechanism to identify SIP messages which belong to the same dialog. However the Call-ID header field is often changed by B2BUAs and other SIP intermediaries in the end-to-end message path.
To solve this problem, a Session-ID header field containing a globally unique session identifier, as defined in RFC 7989 [162], can be used to correlate SIP messages belonging to the same session. In the case of a concatenation of dialogs, the dialog correlation mechanism indicates that these dialogs belong to the same session.
The usage of the Session-ID header field is specified in annex A. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.10.2 CONF usage | In case of the activation of a 3PTY conference, in the INVITE request to the CONF AS the Session-ID header field is added to the URIs in the URI list, in order to indicate the dialogs which are to be included to the 3PTY conference at the CONF AS, as described in 3GPP TS 24.147 [8B]. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.11 Priority mechanisms | In support of priority, the IM CN subsystem uses the mechanisms of RFC 4412 [116]. The request for prioritisation of a transaction / dialog may, for some deployments, be marked with the Resource-Priority header field by the UE. For other deployments, the request is not marked for priority by the UE, but the request is instead identified as a priority request and marked for priority (via a Resource-Priority header field) by a functional entity (e.g., P-CSCF) within the network. Subsequent to successful authorisation at an authorisation point (e.g. AS), request is considered to be authorised.
The characteristics of any priority scheme is defined by the namespace that is used. This determines how priority is applied to the SIP signalling, to the bearer carrying the SIP signalling, and to the bearers carrying any media. Different priority levels exist within each namespace. Priority levels in one namespace have no relationship to the priority levels in any other namespace, i.e. priority level "1" in namespace "A" may have an entirely different level and characteristic of priority treatment to an identically labelled priority level "1" in namespace "B".
A network can support multiple namespaces. It is up to the network operator (potentially based on regulatory or contractural obligations) to define the relationship between the priority mechanisms for each namespace, and indeed with calls that are not given any priority. It is normal that prioritised calls do not have access to 100% of any available resource and indeed are limited to a much lower figure. Priority is optional, and this document places no requirement on a conformant IM CN subsystem implementation to support priority, or indeed any namespace in a priority scheme. Regulators can however place their own requirements on an operator. Emergency transactions or dialogs (see subclause 4.7) can also have their own priority scheme.
RFC 4412 [116] specifies several resource priority namespaces. For example, certain national MPS implementations use resource priority namespaces of ETS (Emergency Telecommunications Service) and WPS (Wireless Priority Service).
Several ways of using priority exist, depending on the authorisation mechanism adopted. These are identified as follows. In each of these authorisation means authorisation to use the service, the namespace, and the priority level within that namespace:
1) Authorisation based on subscription in the IM CN subsystem only, priority requested by the UE using the Resource Priority header field. Whether the user is allowed to use priority or not, and the appropriate namespace and priority levels, is stored as part of the user profile in the HSS. As part of the reg event package subscription, this information is given to the P-CSCF when the contact information for any public user identity changes, and based on this information, the P-CSCF acts as the authorisation point for priority on individual requests. At the P-CSCF, when a Resource-Priority header field is received from the UE, if the requested priority equates to a value (namespace and priority level) that the P-CSCF knows is allowed for that public user identity, the priority is authorised.
2) Authorisation based on a database deployed by an AS; priority requested by the UE using a special dialstring. In this case the user requires no priority subscription information in the HSS. Specific dialstrings are configured in the P-CSCF. When a request is received from the UE by the P-CSCF, if the request contains a specific dialstring that is recognised by the P-CSCF as being eligible for priority treatment, the request is marked for temporary priority, subject to subsequent authorisation by an authorisation point (i.e., AS). And all such requests are routed to an AS. Final authorisation is granted by the AS, based on a PIN or password exchange with the UE. Subsequent requests or responses after authorisation are only given priority by the P-CSCF and S-CSCF if some backwards indication is received for that specific dialog. The definition of this backwards indication is outside the scope of this document (because non-standardised mechanisms have already been implemented in association with this approach).
3) Authorisation based on subscription in the IM CN subsystem and on a database deployed by an AS; priority requested by the UE using a special dialstring. Specific dialstrings are configured in the P-CSCF. When a request is received from the UE by the P-CSCF, if the request contains a specific dialstring that is recognised by the P-CSCF as being eligible for priority treatment, the request is marked for temporary priority, subject to subsequent authorisation by an authorisation point (i.e., AS). Based on iFC functionality that exists at the S-CSCF (from the users subscription in the HSS), such requests are routed to an AS. Final authorisation is granted by the AS, based on a PIN or password exchange with the UE or based on user profile. Subsequent requests or responses after authorisation are only given priority by the P-CSCF and S-CSCF if some backwards indication is received for that specific dialog. The definition of this backwards indication is outside the scope of this document (because non-standardised mechanisms have already been implemented in association with this approach).
Some administrations can require the use of multiple approaches in the same network.
Based on regional/national requirements and network operator policy, registrations from MPS-subscribed UEs can be handled with priority. If the P-CSCF determines that a received SIP REGISTER request is from the MPS-subscribed UE, the P-CSCF should insert an appropriate Resource-Priority header field and treat the request with priority.
NOTE: The mechanism used by the P-CSCF to determine that a UE is an MPS-subscribed UE is implementation specific. For example, all IMS messages from MPS-subscribed UEs can be marked by the P-GW or SMF/UPF with a designated DSCP value (per subclause 11.9 of 3GPP TS 29.061 [11] and subclause 8.3 of 3GPP TS 29.561 [299]) or sent using a designated IP address and port.
For the cases of interworking with other networks, where the P-CSCF of the other network does not support priority, but it is intended or required to give users of that P-CSCF priority in the home network, provision is made for recognition of dialstrings by the IBCF and the S-CSCF. In such scenarios, when the IBCF or S-CSCF recognize that a request contains a dialstring as being eligible for priority treatment, the request is marked by the IBCF or S-CSCF for temporary priority, subject to subsequent authorisation by an authorisation point (i.e. AS). This mechanism does not have an impact on the network where the P-CSCF resides.
Where the network has a requirement to prioritise emergency calls, it can either perform this function by the use of the "esnet" namespace in the Resource-Priority header field (as defined in RFC 7135 [197]), or by recognition of the presence of the service URN relating to an emergency. Where the Resource-Priority header field is used for this purpose, it is inserted by the entity identifying the emergency call, i.e. the P-CSCF or the IBCF. There is no usage of this namespace from the UE, and when this namespace is used, the trust domain implementation is set to remove it if it occurs from the UE.
Where a network has requirements on attestation and signing of priority IMS sessions (e.g., MPS sessions) the Priority verification using assertion of priority information feature described in subclause 3.1 shall be supported and the Calling number verification using signature verification and attestation information feature described in subclause 3.1 may be supported.
Where the network has requirements on attestation and signing of originating calling identification information for emergency and emergency callback IMS sessions, and on authentication of a Resource-Priority header field and a header field value "psap-callback" of a Priority header field, Calling number verification using signature verification and attestation information and Priority verification using assertion of priority information features described in subclause 3.1 shall be supported. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.12 Overload control | Usage of overload control is independent of the nature of any SIP using entity, i.e. there are no specific requirements for any particular IMS functional entity implementing SIP. The capability however is not extended to the UE except when performing the function of an externally attached network.
Two mechanisms are defined as follows:
- a feedback based mechanism defined in RFC 7339 [199], where the feedback is given in the Via header field of signalling messages supporting the traffic. RFC 7339 [199] also defines the default algorithm for usage of the feedback based mechanism in the IM CN subsystem (i.e. loss-based algorithm). Additional algorithms are either already defined, e.g. the rate-based scheme defined in RFC 7415 [200] or can also be defined in the future. As it is carried in the Via header fields the nature of the mechanism is hop by hop.
- an event package for distributing load filters defined in RFC 7200 [201], which can be either used in a hop-by-hop manner between adjacent entities in a similar manner to the feedback based mechanism, or can be used on a wider basis across the network, subject to the restrictions given in annex A. In this manner it can be used to address expected overload situations, e.g. for voting calls initiated by a specific television programme.
When the load filters based mechanism is used in the IMS, the default algorithm is loss-based (i.e. the filter specifies the relative percentage of incoming requests that can be accepted).
The S-CSCF, application servers and entities that implement the additional routeing capability can use both mechanisms in parallel on the same interfaces.
There are no specific reasons why one protocol mechanism should be specified over another, although some discussion is given in the documents specifying the mechanisms themselves. It is regarded as a deployment issue as to which mechanisms are supported, and which algorithms are supported within those mechanisms, beyond those that the mechanisms themselves identify as mandatory. An operator will need to take a network wide view to planning their overload control strategy, it cannot be performed on ad-hoc basis as nodes are deployed.
For the distribution of load filters mechanism, typical deployments might include an S-CSCF subscribing to the load control event package at an AS, an AS subscribing to the load control event package at an AS, and an entity hosting additional routeing capabilities as specified in subclause I.3 subscribing to the load-control event package at the AS.
Based on regional/national requirements and network operator policy, SIP requests that are identified as priority requests are exempted from SIP overload controls up to the point where further exemption would cause network instability.
Based on regional/national requirements and network operator policy, priority calls (e.g., multimedia priority service) are exempted from SIP overload controls up to the point where further exemption would cause network instability. Therefore, SIP messages related to priority calls have the highest priority, and are last to be dropped or rejected, when an IM CN subsystem functional entity decides it is necessary to apply traffic reduction. The interaction between SIP overload control and priority services is covered in RFC 7339 [199] and RFC 7200 [201].
Based on regional/national requirements and network operator policy, emergency calls are exempted from SIP overload controls up to a configured threshold. Therefore, when an IM CN subsystem functional entity decides it is necessary to apply traffic reduction due to overload control, SIP messages related to emergency calls are not dropped while the configured threshold regarding the amount of the ongoing emergency calls is not reached.
Mid-dialog SIP messages have higher priority with regard to initial SIP requests, and therefore are last to be dropped or rejected, when an IM CN subsystem functional entity decides it is necessary to apply traffic reduction due to overload control.
Operation between two network operators is supported. If two network operators wish to implement overload control, it is a matter for bilateral agreement as to what is supported.
Operation with enterprise networks is supported. The network operator and the enterprise operator will need to agree on the overload control options to be supported. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.13 II-NNI traversal scenario | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.13.1 General | Within the IM CN subsystem, the signalling path between a calling user and a called user can be divided into one or more traffic legs, referred to as II-NNI traversal scenarios. Each II-NNI traversal scenario can span networks belonging to different operators and will have its own characteristics that can be different from other II-NNI traversal scenarios in the same call.
Dialog creating SIP requests and standalone requests can contain an "iotl" SIP URI parameter as specified in RFC 7549 [225] in a Request-URI or in one or more Route header fields. The "iotl" SIP URI parameter is appended to the URI representing the end of the II-NNI traversal scenario. The value of "iotl" SIP URI parameter can be used to identify the II-NNI traversal scenario.
If the "iotl" SIP URI parameter is not included in a dialog creating SIP requests or a standalone request, the II-NNI traversal scenario type can be determined by analysing the content of the SIP request or using a default II-NNI traversal scenario type.
NOTE: How the content of the SIP request can be used to determine the II-NNI traversal scenario is implementation dependent and outside the scope of this specification.
The "iotl" SIP URI parameter is included by the start of the II-NNI traversal scenario (e.g. P-CSCF, S-CSCF, BGCF or SCC AS) and removed by the end of the II-NNI traversal scenario (e.g. S-CSCF, TRF or P-CSCF). |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.13.2 Identifying the II-NNI traversal scenario | The "iotl" SIP URI parameter specified in RFC 7549 [225] containing traffic leg information can be used to identify the II-NNI traversal scenario type. The II-NNI traversal scenario type can be used by intermediary entities (e.g. IBCF and transit networks) to make policy decisions related to e.g. media anchoring, screening of SIP signalling, insertion of media functions (e.g. transcoder) and charging.
One example on how the "iotl" SIP URI parameter is included in the Route header field by the P-CSCF in a visited network when sending a request towards the home network is shown below.
EXAMPLE: Route: <sip:ibcf-vA1.visited-A.net;lr>,<sip:[email protected];lr:iotl=visitedA-homeA>
If neither the Request-URI nor any of the Route header fields included in the SIP request contains the "iotl" SIP URI parameter, the II-NNI traversal scenario type can be determined by analysing the content of the SIP request or using a default II-NNI traversal scenario type. The recommended II-NNI traversal scenario type default value is "homeA-homeB".
NOTE: How the content of the SIP request can be used to determine the II-NNI traversal scenario is implementation dependent and outside the scope of this specification. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.13.3 Security aspects | When receiving a dialog creating SIP request or a standalone SIP request from outside the trust domain the IBCF acting as an entry point removes any "iotl" SIP URI parameter according to subclause 4.4.15 and assume the default II-NNI traversal scenario type or can use trusted elements of the SIP request to determine the II‑NNI traversal scenario type.
NOTE: Examples of trusted elements are protocol elements within the trust domain and protocol elements manipulated, checked or added by a previous hop secured by network domain security. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.14 Restoration procedures | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.14.1 General | The present document includes optional restoration procedures for failure of P-CSCF and S-CSCF. The general mechanism is to inform the UE that one of the entities along its registration path is not working, and hence the UE needs to perform an initial registration. For systems providing access to IM CN subsystem using a GPRS IP-CAN, EPS IP-CAN or a 5GS IP-CAN, the mechanism to trigger the UE can be to use the Protocol Configuration Options IE or extended Protocol Configuration Options IE specified in 3GPP TS 24.008 [8], include an 3GPP IM CN subsystem XML body in a 504 (Server Time-out) response, or disconnect the PDN connection. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.14.2 P-CSCF restoration procedures | P-CSCF restoration procedures are implemented in the S-CSCF, the IBCF and the UE.
When the UE originates a session it can detect that a P-CSCF is not reachable based on no response from the P-CSCF in which case the UE selects another P-CSCF if possible and performs a new initial registration.
UDM/HSS or HSS based P-CSCF restoration applies to UE terminating requests where the SIP entity neighbouring the P-CSCF (S-CSCF, IBCF) can detect that a P-CSCF is not reachable. When the neighbouring entity is the S-CSCF, the S-CSCF can in this case initiate the P-CSCF restoration. The S-CSCF sends an indication to the HSS to initiate the restoration. If the terminating user is roaming, the neighbouring entity is an entry IBCF which uses the Restoration-Info header field to inform the S-CSCF about the failure in a 408 (Request Timeout) response for INVITE requests or a 504 (Server Time-out) response for non-INVITE requests and the S-CSCF can send an indication to the HSS to initiate the restoration.
PCF or PCRF based P-CSCF restoration applies to UE terminating INVITE requests. For PCF or PCRF based P-CSCF restoration the S-CSCF uses the Restoration-Info header field to send the IMSI in initial INVITE requests to an alternative P-CSCF. When the user is roaming, the IBCF selects an alternative P-CSCF and forwards the IMSI of the terminating user in a Restoration-Info header field.
Restoration can also be initiated when the P-CSCF has restarted, and lost all bindings for a particular user. In this case the P-CSCF rejects the incoming request with a 404 (Not Found) response. If the home network applies UDM/HSS or HSS based P-CSCF restoration the S-CSCF initiates the restoration procedure by sending an indication to the HSS. If PCF or PCRF based restoration is used, the S-CSCF initiate the PCF or PCRF based P-CSCF restoration procedure for the served user by including the IMSI in a Restoration-Header field included in an initial INVITE request.
NOTE: In the rest of the present document where the "PCRF based P-CSCF restoration" procedure is mentioned the "PCF based P-CSCF restoration" procedure also applies, and where the "HSS based P-CSCF restoration" procedure is mentioned the "UDM/HSS based P-CSCF restoration" procedure also applies. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.14.3 S-CSCF restoration procedures | The P-CSCF can inform the UE about S-CSCF failures in a 504 (Server Time-out) response using the 3GPP IM CN subsystem XML body defined in subclause 7.6, in accordance with subclause 5.2.6.3.2A, when the P-CSCF is unable to forward a request to an S-CSCF.
When the S-CSCF receives a request initiated by the served user for which the S-CSCF does not have the user profile or does not trust the data that it has (e.g. due to restart) the S-CSCF can if it fails to retrieve the data from the HSS trigger a registration by sending a 504 (Server Time-out) response using the 3GPP IM CN subsystem XML body defined in subclause 7.6 to the UE, in accordance with subclause 5.4.3.2.
An I-CSCF can reselect S-CSCF if the previously selected S-CSCF is not available.
If an IBCF acting as an entry point in the originating home network cannot forward the request the IBCF can trigger the UE to perform initial registration by including the 3GPP IM CN subsystem XML body in a 504 (Server Time-out) response, in accordance with subclause 5.10.3.5. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.15 Resource sharing | Resource sharing allows two or more sessions to use the same resources for one or more media streams in uplink, downlink or both uplink and downlink direction.
A P-CSCF that supports resource sharing can determine that there is a potential for resource sharing based on local configuration or defer the determination of potential resource sharing to an AS in the home network.
If the determination of potential resource sharing is deferred to an AS in the home network:
- the P-CSCF on the originating side indicates that resource sharing is supported in the initial REGISTER request in the Resource-Share header field defined in subclause 7.2.13. The Resource-Share header field is included in the third-party REGISTER request towards the AS; and
- if the "message/sip" MIME body in the third-party REGISTER request included the Resource-Share header field with the value "supported", the AS in the home network includes the Resource-Share header field containing the rules for resource sharing in responses and requests towards the P-CSCF.
If the rules for resource sharing are updated, the updated rule will be sent to P-CSCF in one of the sessions that share resources. The updated resource sharing rules will then be applied for all sessions that are sharing resources.
NOTE: In this release of the technical specification the UE cannot indicate support of resource sharing. However, the Resource-Share header field is not removed from requests and responses towards the UE and the UE can use the information in the header field to adapt its behaviour according to the information. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.16 Priority sharing | Priority sharing allows two or more sessions with different priority to share the same bearer.
The determination of the use of priority sharing is deferred to an AS in the home network:
1) if P-CSCF supports priority sharing and if according to local policy, the P-CSCF indicate that priority sharing is supported by including the g.3gpp.priority-share feature-capability indicator defined in subclause 7.9A.10 in a Feature-Caps header field in the REGISTER request;
NOTE: The Feature-Caps header field with the g.3gpp.priority-share feature-capability indicator is included in the "message/sip" MIME body in the third-party REGISTER request sent over the ISC interface.
2) if the "message/sip" MIME body in the third-party REGISTER request included the g.3gpp.priority-share feature-capability indicator and:
a) if the AS determined to enable priority sharing, the AS includes the Priority-Share header field with a value "allowed" in a request or response sent towards the P-CSCF; or
b) if the AS determined to disable priority sharing, the AS includes the Priority-Share header field with a value "not-allowed" in a request or response sent towards the P-CSCF. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.17 3GPP PS data off | The UE and the network can support the 3GPP PS data off.
When 3GPP PS data off is supported and active, IP packets that are associated with services that are not a 3GPP PS data off exempt service are prevented from transport over EPS IP-CAN, GPRS IP-CAN and 5GS IP-CAN as specified in 3GPP TS 23.228 [7]. The UE may be configured by the HPLMN, the EHPLMN or the subscribed SNPN with up to two indications whether a 3GPP IMS service is a 3GPP PS Data Off exempt service, one indication is valid when the UE is in the HPLMN, the EHPLMN, or a subscribed SNPN and the other indication is valid when the UE is in the VPLMN or, if the UE supports access to an SNPN using credentials from a CH, a non-subscribed SNPN. When the UE is only configured with the indication valid for the UE camping in HPLMN the EHPLMN or a subscribed SNPN, the UE shall use this indication also when the UE is in the VPLMN or the non-subscribed SNPN.
When 3GPP PS data off is supported and active and the UE is configured, either as specified in 3GPP TS 24.167 [8G], 3GPP TS 24.275 [301] or in 3GPP TS 31.102 [15C], with services that are 3GPP PS data off exempt, then the UE will not send uplink IP packets related to any services that are not 3GPP PS data off exempt over EPS IP-CAN, GPRS IP-CAN and 5GS IP-CAN. The UE informs the network about its 3GPP PS data off status by including a g.3gpp.ps-data-off media feature tag specified in subclauce 7.9.8 in all REGISTER requests sent over GPRS IP-CAN, EPS IP-CAN or 5GS IP-CAN. The UE reregisters over EPS IP-CAN, GPRS IP-CAN and 5GS IP-CAN every time the 3GPP PS data off status is changed or the UE is provided by the network with a new list of 3GPP PS data off exempt services while the 3GPP PS data off status is "active".
An AS handling a service is configured with information whether the service is a 3GPP PS data off exempt service. If the 3GPP PS data off status is active and the service is not a 3GPP PS data off exempt service, the AS prevents downlink IP packets of the service from reaching the UE over EPS IP-CAN, GPRS IP-CAN and 5GS IP-CAN. The AS shall be configured with up to two indications whether a 3GPP IMS service is a 3GPP PS Data Off exempt service, one indication is valid for non-roaming users, and the other indication is valid for users roaming in the various VPLMNs with whom roaming agreements exist or users accessing non-subscribed SNPNs. When the AS is only configured with the indication valid for the UE camping in the HPLMN, the EHPLMN or the subscribed SNPN, the AS shall use this indication also when the UE is in the VPLMN or non-subscribed SNPN. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.18 Dynamic Service Interaction | Dynamic Service Interaction allows that different ASs involved in the same IMS session (within an operator network or across networks) exchange information about executed services to avoid conflicting interactions between these services. Dynamic Service Interaction information is included in a SIP header field Service-Interact-Info defined in subclause 7.2.14.
If an AS which supports dynamic service interaction:
- provides one or more services:
a) the AS inserts in a SIP message the Service-Interact-Info header field with the identities of the services which have been performed; and
b) if the AS identified services which should be further avoided the AS adds the identities of those services in the Service-Interact-Info header field; and
- receives a SIP message containing the Service-Interact-Info header field, the AS takes the received Service-Interact-Info header field information into account as described in subclause 7.2.14.3. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 4.19 Restricted Local Operator Services | The UE and the network can support Restricted Local Operator Services (RLOS).
RLOS services are operator defined services that are offered to UEs when using an EPS IP-CAN as specified in annex L in the following scenarios:
- UE is successfully registered using IMS AKA or GPRS-IMS bundled authentication; or
- UE has attempted to register and the registration is rejected from the network with a 403 (Forbidden) response.
RLOS services are offered only for the UE-originating case.
RLOS services can be offered to an operator's own subscribers and roaming subscribers.
4.20 IMS data channel
The UE and the network can support the IMS data channel procedures as specified in 3GPP TS 23.228 [7] and 3GPP TS 24.186 [297].
IMS data channels are always associated with MMTEL sessions. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5 Application usage of SIP | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1 Procedures at the UE | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.0 General | The UE procedures for UE detectable emergency calls are defined in subclause 5.1.6. Exceptions to UE procedures for SIP that do not relate to emergency, are documented in subclause 5.1.6 and shall apply. These exceptions include handling of a response to a request not detected by the UE as relating to an emergency.
When sending a failure response to any received request, depending on operator policy, the UE may insert a Response-Source header field with an "fe" header field parameter constructed with the URN namespace "urn:3gpp:fe", the fe-id part of the URN set to "ue" and optionally an appropriate fe-param part of the URN set in accordance with subclause 7.2.17. A UE when sending a failure response will add in the URN the "side" header field parameter set to:
- "orig" for a UE-originating case; and
- "term" for a UE-terminating case. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1 Registration and authentication | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.1 General | The UE shall register public user identities (see table A.4/1 and dependencies on that major capability).
NOTE 1: The UE can use multiple Contact header field values simultaneously containing the same IP address and port number in the contact address.
In case a UE registers several public user identities at different points in time, the procedures to reregister, deregister and subscribe to the registration-state event package for these public user identities can remain uncoordinated in time.
The UE can register any one of its public user identities with any IP address acquired by the UE. The same public user identity can be bound to more than one IP address of the UE. While having valid registrations of previously registered public user identities, the UE can register any additional public user identity with any of its IP addresses. When binding any one of its public user identities to an additional contact address, the UE shall follow the procedures described in RFC 5626 [92].
If SIP digest without TLS is used, the UE shall not include signalling plane security mechanisms in the header fields defined in RFC 3329 [48] in any SIP messages.
NOTE 2: The UE determines if SIP digest is used with or without TLS based on device configuration. If SIP digest with TLS is used, then the UE includes the TLS signalling plane security mechanism in the header fields defined in RFC 3329 [48] as described in subclause 5.1.1.2.4.
SIP requests that indicate security mechanisms for both the signalling plane and the media plane can contain multiple instances or a single instance of the Security-Client, Security-Verify, or Security-Server header fields defined in RFC 3329 [48].
In case a device performing address and/or port number conversions is provided by a NA(P)T or NA(P)T-PT, the UE may need to modify the SIP contents according to the procedures described in either annex F or annex K.
NOTE 3: If UE populates the display-name of the Contact header field included in the REGISTER request with UE name, other UEs of the user can discover the UE name of the UE in the reg event package notification. The UE name is a text string chosen by the user allowing the user to distinguish individual UEs of the same user.
5.1.1.1A Parameters contained in the ISIM
This subclause applies when a UE contains either an ISIM or a USIM.
The ISIM shall always be used for authentication to the IM CN subsystem, if it is present, as described in 3GPP TS 33.203 [19].
The ISIM is preconfigured with all the necessary parameters to initiate the registration to the IM CN subsystem. These parameters include:
- the private user identity;
- one or more public user identities; and
- the home network domain name used to address the SIP REGISTER request
The first public user identity in the list stored in the ISIM is used in emergency registration requests.
In case the UE does not contain an ISIM, the UE shall:
- generate a private user identity;
- generate a temporary public user identity; and
- generate a home network domain name to address the SIP REGISTER request to;
in accordance with the procedures in clause C.2.
The temporary public user identity is only used in REGISTER requests, i.e. initial registration, re-registration, UE-initiated deregistration.
The UE shall not reveal to the user the temporary public user identity if the temporary public user identity is barred. The temporary public user identity is not barred if received by the UE in the P-Associated-URI header field.
If the UE is unable to derive the parameters in this subclause for any reason, then the UE shall not proceed with the request associated with the use of these parameters and will not be able to register to the IM CN subsystem.
5.1.1.1B Parameters provisioned to a UE without ISIM or USIM
5.1.1.1B.1 Parameters provisioned in the IMC
In case the UE contains neither an ISIM nor a USIM, but IMC is present the UE shall use preconfigured parameters in the IMC to initiate the registration to the IM CN subsystem and for authentication.
The following IMS parameters are assumed to be available to the UE:
- a private user identity;
- a public user identity; and
- a home network domain name to address the SIP REGISTER request to.
These parameters may not necessarily reside in a UICC.
The first public user identity in the list stored in the IMC is used in emergency registration requests.
5.1.1.1B.2 Parameters when UE does not contain ISIM, USIM or IMC
If the UE contains neither ISIM, nor USIM nor IMC, the UE shall generate a temporary public user identity, a private user identity and a home network domain name to address the SIP REGISTER request to, according 3GPP TS 23.003 [3]. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.2 Initial registration | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.2.1 General | The initial registration procedure consists of the UE sending an unprotected REGISTER request and, if challenged depending on the security mechanism supported for this UE, sending the integrity-protected REGISTER request or other appropriate response to the challenge. The UE can register a public user identity with any of its contact addresses at any time after it has acquired an IP address, discovered a P-CSCF, and established an IP-CAN bearer that can be used for SIP signalling. However, the UE shall only initiate a new registration procedure when it has received a final response from the registrar for the ongoing registration, or the previous REGISTER request has timed out.
When registering any public user identity belonging to the UE, the UE shall either use an already active pair of security associations or a TLS session to protect the REGISTER requests, or register the public user identity via a new initial registration procedure.
When binding any one of its public user identities to an additional contact address via a new initial registration procedure, the UE shall follow the procedures described in RFC 5626 [92]. The set of security associations or a TLS session resulting from this initial registration procedure will have no impact on the existing set of security associations or TLS sessions that have been established as a result of previous initial registration procedures. However, if the UE registers any one of its public user identities with a new contact address via a new initial registration procedure and does not employ the procedures described in RFC 5626 [92], then the new set of security associations or TLS session shall replace any existing set of security association or TLS session.
If the UE detects that the existing security associations or TLS sessions associated with a given contact address are no longer active (e.g., after receiving no response to several protected messages), the UE shall:
- consider all previously registered public user identities bound to this security associations or TLS session that are only associated with this contact address as deregistered; and
- stop processing all associated ongoing dialogs and transactions that were using the security associations or TLS session associated with this contact address, if any (i.e. no further SIP signalling will be sent by the UE on behalf of these transactions or dialogs).
The UE shall send the unprotected REGISTER requests to the port advertised to the UE during the P-CSCF discovery procedure. If the UE does not receive any specific port information during the P-CSCF discovery procedure, or if the UE was pre-configured with the P-CSCF's IP address or domain name and was unable to obtain specific port information, the UE shall send the unprotected REGISTER request to the SIP default port values as specified in RFC 3261 [26].
NOTE 1: The UE will only send further registration and subsequent SIP messages towards the same port of the P-CSCF for security mechanisms that do not require to use negotiated ports for exchanging protected messages.
The UE shall extract or derive a public user identity, the private user identity, and the domain name to be used in the Request-URI in the registration, according to the procedures described in subclause 5.1.1.1A or subclause 5.1.1.1B. A public user identity may be input by the end user.
On sending an unprotected REGISTER request, the UE shall populate the header fields as follows:
a) a From header field set to the SIP URI that contains:
1) if the UE supports RFC 6140 [191] and performs the functions of an external attached network, the main URI of the UE; else
2) the public user identity to be registered;
b) a To header field set to the SIP URI that contains:
1) if the UE supports RFC 6140 [191] and performs the functions of an external attached network, the main URI of the UE; else
2) the public user identity to be registered;
c) a Contact header field set to include SIP URI(s) containing the IP address or FQDN of the UE in the hostport parameter. If the UE:
1) supports GRUU (see table A.4, item A.4/53);
2) supports multiple registrations;
3) has an IMEI available; or
4) has an MEID available;
the UE shall include a "+sip.instance" header field parameter containing the instance ID. Only the IMEI shall be used for generating an instance ID for a multi-mode UE that supports both 3GPP and 3GPP2 defined radio access networks.
NOTE 2: The requirement placed on the UE to include an instance ID based on the IMEI or the MEID when the UE does not support GRUU and does not support multiple registrations does not imply any additional requirements on the network.
If the UE supports multiple registrations it shall include a "reg-id" header field parameter as described in RFC 5626 [92].
The UE shall include all supported ICSI values (coded as specified in subclause 7.2A.8.2) in a g.3gpp.icsi-ref media feature tag as defined in subclause 7.9.2 and RFC 3840 [62] for the IMS communication services it intends to use, and IARI values (coded as specified in subclause 7.2A.9.2), for the IMS applications it intends to use in a g.3gpp.iari-ref media feature tag as defined in subclause 7.9.3 and RFC 3840 [62].
The UE shall include the media feature tags defined in RFC 3840 [62] and RFC 5688 [120] for all supported streaming media types.
If the UE supports RFC 6140 [191] and performs the functions of an external attached network, for the registration of bulk number contacts the UE shall include a Contact URI without a user portion and containing the "bnc" URI parameter.
If the UE has no specific reason not to include a user part in the URI of the contact address (eg. some UE performing the functions of an external attached network), the UE should include a user part in the URI of the contact address such that the user part is globally unique and does not reveal any private information;
NOTE 3: A time-based UUID (Universal Unique Identifier) generated as per subclause 4.2 of RFC 4122 [154] is globally unique and does not reveal any private information.
d) a Via header field set to include the sent-by field containing the IP address or FQDN of the UE and the port number where the UE expects to receive the response to this request when UDP is used. For TCP, the response is received on the TCP connection on which the request was sent. For the UDP, the UE shall also include a "rport" header field parameter with no value in the Via header field. Unless the UE has been configured to not send keep-alives, and unless the UE is directly connected to an IP-CAN for which usage of NAT is not defined, it shall include a "keep" header field parameter with no value in the Via header field, in order to indicate support of sending keep-alives associated with the registration, as described in RFC 6223 [143];
NOTE 4: When sending the unprotected REGISTER request using UDP, the UE transmit the request from the same IP address and port on which it expects to receive the response to this request.
e) a registration expiration interval value of 600 000 seconds as the value desired for the duration of the registration;
NOTE 5: The registrar (S-CSCF) might decrease the duration of the registration in accordance with network policy. Registration attempts with a registration period of less than a predefined minimum value defined in the registrar will be rejected with a 423 (Interval Too Brief) response.
f) a Request-URI set to the SIP URI of the domain name of the home network used to address the REGISTER request;
g) the Supported header field containing the option-tag "path", and
1) if GRUU is supported, the option-tag "gruu"; and
2) if multiple registrations is supported, the option-tag "outbound".
h) if a security association or TLS session exists, and if available to the UE (as defined in the access technology specific annexes for each access technology), a P-Access-Network-Info header field set as specified for the access network technology (see subclause 7.2A.4);
i) a Security-Client header field to announce the media plane security mechanisms the UE supports, if any, labelled with the "mediasec" header field parameter specified in subclause 7.2A.7;
NOTE 6: The "mediasec" header field parameter indicates that security mechanisms are specific to the media plane.
j) if the UE supports RFC 6140 [191] and performs the functions of an external attached network, for the registration of bulk number contacts the UE shall include a Require header field containing the option-tag "gin"; and
k) if the UE supports RFC 6140 [191] and performs the functions of an external attached network, for the registration of bulk number contacts the UE shall include a Proxy-Require header field containing the option-tag "gin".
On receiving a 401 (Unauthorized) response to the REGISTER request, the UE shall:
a) if available, store the announcement of media plane security mechanisms the P-CSCF (IMS-ALG) supports labelled with the "mediasec" header field parameter specified in subclause 7.2A.7 and received in the Security-Server header field, if any. Once the UE chooses a media security mechanism from the list received in the Security-Server header field from the server, the UE may initiate that mechanism on a media level when it initiates new media in an existing session.
NOTE 7: The "mediasec" header field parameter indicates that security mechanisms are specific to the media plane.
On receiving the 200 (OK) response to the REGISTER request, the UE shall:
a) store the expiration time of the registration for the public user identities found in the To header field value and bind it either to the respective contact address of the UE or to the registration flow and the associated contact address (if the multiple registration mechanism is used);
NOTE 8: If the UE supports RFC 6140 [191] and performs the functions of an external attached network, the To header field will contain the main URI of the UE.
b) store as the default public user identity the first URI on the list of URIs present in the P-Associated-URI header field and bind it to the respective contact address of the UE and the associated set of security associations or TLS session;
NOTE 9: When using the respective contact address and associated set of security associations or TLS session, the UE can utilize additional URIs contained in the P-Associated-URI header field and bound it to the respective contact address of the UE and the associated set of security associations or TLS session, e.g. for application purposes.
c) treat the identity under registration as a barred public user identity, if it is not included in the P-Associated-URI header field;
d) store the list of service route values contained in the Service-Route header field and bind the list either to the contact address or to the registration flow and the associated contact address (if the multiple registration mechanism is used), and the associated set of security associations or TLS session over which the REGISTER request was sent;
NOTE 10: When multiple registration mechanism is not used, there will be only one list of service route values bound to a contact address. However, when multiple registration mechanism is used, there will be different list of service route values bound to each registration flow and the associated contact address.
NOTE 11: The UE will use the stored list of service route values to build a proper preloaded Route header field for new dialogs and standalone transactions (other than REGISTER method) when using either the respective contact address or the registration flow and the associated contact address (if the multiple registration mechanism is used), and the associated set of security associations or TLS session.
e) if the UE indicated support for GRUU in the Supported header field of the REGISTER request then:
- if the UE did not use the procedures specified in RFC 6140 [191] for registration, find the Contact header field within the response that matches the one included in the REGISTER request. If this contains a "pub-gruu" header field parameter or a "temp-gruu" header field parameter or both, then store the value of those parameters as the GRUUs for the UE in association with the public user identity and the contact address that was registered; and
- if the UE used the procedures specified in RFC 6140 [191] for registration then find the Contact header field within the response that matches the one included in the REGISTER request. If this contains a "pub-gruu" header field parameter then store the value of the "pub-gruu" header field parameter for use for generating public GRUUs for registering UAs as specified in RFC 6140 [191]. If this contains a "temp-gruu-cookie" header field parameter then store the value of the "temp-gruu-cookie" header field parameter for use for generating temporary GRUUs for registering UAs as specified in RFC 6140 [191];
NOTE 12: When allocating public GRUUs to registering UAs the functionality within the UE that performs the role of registrar will add an "sg" SIP URI parameter that uniquenly identifies that UA to the public GRUU it received in the "pub-gruu" header field parameter. The procedures for generating a temporary GRUU using the "temp-gruu-cookie" header field parameter are specified in subclause 7.1.2.2 of RFC 6140 [191].
f) if the REGISTER request contained the "reg-id" and "+sip.instance" Contact header field parameter and the "outbound" option tag in a Supported header field, the UE shall check whether the option-tag "outbound" is present in the Require header field:
- if no option-tag "outbound" is present, the UE shall conclude that the S-CSCF does not support the registration procedure as described in RFC 5626 [92], and the S-CSCF has followed the registration procedure as described in RFC 5627 [93] or RFC 3261 [26], i.e., if there is a previously registered contact address, the S-CSCF replaced the old contact address and associated information with the new contact address and associated information (see bullet e) above). Upon detecting that the S-CSCF does not support the registration procedure as defined in RFC 5626 [92], the UE shall refrain from registering any additional IMS flows for the same private identity as described in RFC 5626 [92]; or
NOTE 13: Upon replaces the old contact address with the new contact address, the S-CSCF performs the network-initiated deregistration procedure for the previously registered public user identities and the associated old contact address as described in subclause 5.4.1.5. Hence, the UE will receive a NOTIFY request informing the UE about the deregistration of the old contact address.
- if an option-tag "outbound" is present, the UE may establish additional IMS flows for the same private identity, as defined in RFC 5626 [92];
g) if available, store the announcement of media plane security mechanisms the P-CSCF (IMS-ALG) supports labelled with the "mediasec" header field parameter specified in subclause 7.2A.7 and received in the Security-Server header field, if any. Once the UE chooses a media security mechanism from the list received in the Security-Server header field from the server, it may initiate that mechanism on a media level when it initiates new media in an existing session;
NOTE 14: The "mediasec" header field parameter indicates that security mechanisms are specific to the media plane.
h) if the Via header field contains a "keep" header field parameter with a value, unless the UE detects that it is not behind a NAT, start to send keep-alives associated with the registration towards the P-CSCF, as described in RFC 6223 [143];
i) if a Feature-Caps header field, as specified in RFC 6809 [190] is received, a UE supporting the Feature-Caps header field shall consider the ICSI values received in the Feature-Caps header field of 200 (OK) response as supported by the IM subsystem for the established registration or registration flow (if the multiple registration mechanism is used);
NOTE 15: The UE and related applications can use the ICSI values received in the Feature-Caps header field of 200 (OK) response to improve the user experience.
j) void; and
k) if the 200 (OK) response includes a Feature-Caps header field, as specified in RFC 6809 [190], with a "+g.3gpp.verstat" header field parameter and if the UE supports calling number verification status determination, determine that the home network supports calling number verification using signature verification and attestation information, as defined in subclause 3.1.
On receiving a 305 (Use Proxy) response to the unprotected REGISTER request, unless otherwise specified in access specific annexes (as described in annex B, annex L or annex U), the UE shall:
a) ignore the contents of the Contact header field if it is included in the received message;
NOTE 16: The 305 response is not expected to contain a Contact header field.
b) release all IP-CAN bearers used for the transport of media according to the procedures in subclause 9.2.2;
c) initiate either a new P-CSCF discovery procedure as described in subclause 9.2.1, or select a new P-CSCF, if the UE was pre-configured with more than one P-CSCF's IP addresses or domain names;
d) select a P-CSCF address, which is different from the previously used address, from the address list; and
e) perform the procedures for initial registration as described in subclause 5.1.1.2.
On receiving a 423 (Interval Too Brief) response to the REGISTER request, the UE shall:
- send another REGISTER request populating the registration expiration interval value with an expiration timer of at least the value received in the Min-Expires header field of the 423 (Interval Too Brief) response.
On receiving a 408 (Request Timeout) response or 500 (Server Internal Error) response or 504 (Server Time-Out) or 600 (Busy Everywhere) response or 403 (Forbidden) response for an initial registration, the UE may attempt to perform initial registration again.
When the timer F expires at the UE, the UE:
a) shall mark the currently used P-CSCF address as unavailable for the last duration of the retry delay time computed by the algorithm defined in subclause 4.5 of RFC 5626 [92] plus 5 minutes;
b) if there is a locally stored P-CSCF address as specified in subclause 5.1.9 which is different from the currently used P-CSCF address and which is not marked as unavailable, may initiate an initial registration as specified in subclause 5.1.1.2 using that P-CSCF; and
c) if there is no locally stored P-CSCF address as specified in subclause 5.1.9 which is different from the currently used P-CSCF address and which is not marked as unavailable, may get a new set of P-CSCF-addresses as described in subclause 9.2.1 unless otherwise specified in the access specific annexes (as described in annex B, annex L or annex U) and initiate an initial registration as specified in subclause 5.1.1.2.
NOTE 17: It is an implementation option whether these actions are also triggered by other means than expiration of timer F, e.g. based on ICMP messages.
On receiving a 4xx, 5xx (except 503) or 6xx response to the REGISTER request, whereby the response contains a Retry-After header field, the UE shall not automatically attempt an initial registration via the same IP-CAN and the same P-CSCF for the amount of time indicated in the Retry-After header field. If the UE is power cycled, the UE can attempt an initial registration. If no initial registration occurs within the time period indicated by the Retry-After header field, the counter of unsuccessful initial registration attempts is reset.
On receiving a 503 response with a Retry-After header field to the REGISTER request and the Retry-After header field indicates time bigger than the value for timer F as specified in table 7.7.1, the UE:
a) shall mark the currently used P-CSCF address as unavailable for the time indicated by the Retry-After header field;
b) if there is a locally stored P-CSCF address as specified in subclause 5.1.9 which is different from the currently used P-CSCF address and which is not marked as unavailable, may initiate an initial registration as specified in subclause 5.1.1.2 using that P-CSCF; and
c) if there is no locally stored P-CSCF address as specified in subclause 5.1.9 which is different from the currently used P-CSCF address and which is not marked as unavailable, may get a new set of P-CSCF addresses as described in subclause 9.2.1 unless otherwise specified in the access specific annexes (as described in annex B, annex L or annex U) and initiate an initial registration as specified in subclause 5.1.1.2.
NOTE 18: if the Retry-After header field indicates time smaller than the value for timer F as specified in table 7.7.1, the UE continues using the currently used P-CSCF address.
For each 4xx, 5xx or 6xx response received without a Retry-After header field to the REGISTER request, the UE shall:
a) use the mechanism defined in subclause 4.5 of RFC 5626 [92] for determination of the retry delay time before each new registration attempt;
b) mark the currently used P-CSCF address as unavailable for the last duration of the retry delay time computed by the algorithm defined in subclause 4.5 of RFC 5626 [92] plus 5 minutes; and
c) initiate an initial registration as specified in subclause 5.1.1.2 after the amount of time of the last retry delay time computed by the algorithm defined in subclause 4.5 of RFC 5626 [92]; and
- if there is a locally stored P-CSCF address as specified in subclause 5.1.9 which is different from the currently used P-CSCF address and which is not marked as unavailable, may initiate the initial registration using that P-CSCF; and
- if there is no locally stored P-CSCF address as specified in subclause 5.1.9 which is different from the currently used P-CSCF address and which is not marked as unavailable, may get a new set of P-CSCF addresses as described in subclause 9.2.1 unless otherwise specified in the access specific annexes (as described in annex B, annex L or annex U) and initiate the initial registration as specified in subclause 5.1.1.2.
The values of max-time and base-time (if all failed) may be provided by the network to the UE with the management objects specified in 3GPP TS 24.167 [8G]. If no values of the parameters max-time and base-time (if all failed) have been provided to the UE by the network, the default values defined in subclause 4.5 of RFC 5626 [92] shall be used. Other mechanisms may be used as well and are outside the scope of the present document.
NOTE 19: If the UE stops initiating initial registration, the UE can attempt to perform initial registration with the network again based on the local configuration and not wait till power-cycled. The local configuration is outside the scope of this specification. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.2.2 Initial registration using IMS AKA | On sending a REGISTER request, as defined in subclause 5.1.1.2.1, the UE shall additionally populate the header fields as follows:
a) an Authorization header field, with:
- the "username" header field parameter, set to the value of the private user identity;
- the "realm" header field parameter, set to the domain name of the home network;
- the "uri" header field parameter, set to the SIP URI of the domain name of the home network;
- the "nonce" header field parameter, set to an empty value; and
- the "response" header field parameter, set to an empty value;
NOTE 1: If the UE specifies its FQDN in the hostport parameter in the Contact header field and in the sent-by field in the Via header field, then it has to ensure that the given FQDN will resolve (e.g., by reverse DNS lookup) to the IP address that is bound to the security association.
NOTE 2: The UE associates two ports, a protected client port and a protected server port, with each pair of security association. For details on the selection of the port values see 3GPP TS 33.203 [19].
b) additionally for the Contact header field, if the REGISTER request is protected by a security association, include the protected server port value in the hostport parameter;
c) additionally for the Via header field, for UDP, if the REGISTER request is protected by a security association, include the protected server port value in the sent-by field; and
d) a Security-Client header field set to specify the signalling plane security mechanism the UE supports, the IPsec layer algorithms the UE supports and the parameters needed for the security association setup. The UE shall support the setup of two pairs of security associations as defined in 3GPP TS 33.203 [19]. The syntax of the parameters needed for the security association setup is specified in annex H of 3GPP TS 33.203 [19]. The UE shall support the "ipsec-3gpp" security mechanism, as specified in RFC 3329 [48]. The UE shall support the IPsec layer algorithms for integrity and confidentiality protection as defined in 3GPP TS 33.203 [19], and shall announce support for them according to the procedures defined in RFC 3329 [48].
On receiving the 200 (OK) response to the REGISTER request defined in subclause 5.1.1.2.1, the UE shall additionally:
1) If the UE supports multiple registrations and the REGISTER request contained the "+sip.instance" header field parameter and the "reg-id" header field parameter in the Contact header field, and the "outbound" option-tag in the Supported header field, the UE shall check whether the option-tag "outbound" is present in the Require header field. If the option-tag "outbound" is present, then the UE shall use the bidirectional flow as defined in RFC 5626 [92] as follows:
a) for UDP, the bidirectional flow consists of two unidirectional flows, i.e. the first unidirectional flow is identified with the UE's protected client port, the P-CSCF's protected server port, and the respective IP addresses. The UE uses this flow to send the requests and responses to the P-CSCF. The second unidirectional flow is identified with the P-CSCF's protected client port, the UE's protected server port and the IP addresses. The second unidirectional flow is used by the UE to receive the requests and responses from the P-CSCF; or
b) for TCP, the bidirectional flow is the TCP connection between the UE and the P-CSCF. This TCP connection was established by the UE, i.e. from the UE's protected client port and the UE's IP address to the P-CSCF's protected server port and the P-CSCF's IP address. This TCP connection is used to exchange SIP messages between the UE and the P-CSCF; and
2) set the security association lifetime to the longest of either the previously existing security association lifetime (if available), or the lifetime of the just completed registration plus 30 seconds.
NOTE 3: If the UE receives Authentication-Info, it will proceed as described in RFC 3310 [49] when AKAv1 is used or as described in RFC 4169 [227] when AKAv2 is used.
When a 401 (Unauthorized) response to a REGISTER is received the UE shall behave as described in subclause 5.1.1.5.1. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.2.3 Initial registration using SIP digest without TLS | On sending a REGISTER request, as defined in subclause 5.1.1.2.1, the UE shall additionally populate the header fields as follows:
a) an Authorization header field as defined in RFC 7616 [286] and RFC 8760 [287] unless otherwise specified in the access specific annexes, with:
- the "username" header field parameter, set to the value of the private user identity;
- the "realm" header field parameter, set to the domain name of the home network;
- the "uri" header field directive, set to the SIP URI of the domain name of the home network;
- the "nonce" header field parameter, set to an empty value; and
- the "response" header field parameter, set to an empty value;
b) the hostport parameter in the Contact header field with the port value of an unprotected port where the UE expects to receive subsequent requests; and
c) the sent-by field in the Via header field with the port value of an unprotected port where the UE expects to receive responses to the request.
The UE shall use the locally available public user identity, the private user identity, and the domain name to be used in the Request-URI in the registration. The method whereby the public user identity and private user identity are made available to the UE is outside the scope of this document (e.g. a public user identity could be input by the end user).
When a 401 (Unauthorized) response to a REGISTER is received the UE shall behave as described in subclause 5.1.1.5.4. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.2.4 Initial registration using SIP digest with TLS | On sending a REGISTER request, as defined in subclause 5.1.1.2.1, the UE shall additionally populate the header fields as follows:
a) an Authorization header field set in accordance with subclause 5.1.1.2.3 unless otherwise specified in the access specific annexes; and
b) a Security-Client header field set to specify the signalling plane security mechanism the UE supports. The UE shall support the setup of a TLS session as defined in 3GPP TS 33.203 [19]. The UE shall support the "tls" security mechanism, as specified in RFC 3329 [48]. The UE shall support TLS for integrity and confidentiality protection as defined in RFC 3261 [26], and shall announce support for them according to the procedures defined in RFC 3329 [48].
On receiving the 200 (OK) response to the REGISTER request defined in subclause 5.1.1.2.1, the UE shall additionally:
a) set the TLS session lifetime to the longest of either the previously existing TLS session lifetime (if available), or the lifetime of the just completed registration plus 30 seconds.
If a UE supports TLS, then the UE shall support TLS ciphersuites as described in 3GPP TS 33.203 [19]. TLS session lifetime is determined by local configuration of the UE.
For SIP digest with TLS, the UE associates a protected server port with the TLS session port on the UE.
When a 401 (Unauthorized) response to a REGISTER is received the UE shall behave as described in subclause 5.1.1.5.6. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.2.5 Initial registration using NASS-IMS bundled authentication | On sending a REGISTER request, as defined in subclause 5.1.1.2.1, the UE shall additionally populate the header fields as follows:
a) optionally, an Authorization header field, with the "username" header field parameter, set to the value of the private user identity;
NOTE 1: In case the Authorization header field is absent, the mechanism only supports that one public user identity is associated with only one private user identity. The public user identity is set so that it is possible to derive the private user identity from the public user identity by removing SIP URI scheme and the following parts of the SIP URI if present: port number, URI parameters, and To header field parameters.
On receiving the 200 (OK) response to the REGISTER request defined in subclause 5.1.1.2.1, there are no additional requirements for the UE.
NOTE 2: When NASS-IMS bundled authentication is in use, a 401 (Unauthorized) response to the REGISTER request is not expected to be received. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.2.6 Initial registration using GPRS-IMS-Bundled authentication | On sending a REGISTER request, as defined in subclause 5.1.1.2.1, the UE shall additionally populate the header fields as follows:
a) an Authorization header field as defined in RFC 7616 [286] and RFC 8760 [287] shall not be included, in order to indicate support for GPRS-IMS-Bundled authentication.
b) the Security-Client header field as defined in RFC 3329 [48] shall not contain signalling plane security mechanisms;
c) a From header field set to a temporary public user identity as defined in 3GPP TS 23.003 [3], as the public user identity to be registered;
d) a To header field set to a temporary public user identity as defined in 3GPP TS 23.003 [3], as the public user identity to be registered;
e) the Contact header field with the port value of an unprotected port where the UE expects to receive subsequent mid-dialog requests; and
f) the Via header field with the port value of an unprotected port where the UE expects to receive responses to the request.
NOTE 1: Since the private user identity is not included in the REGISTER requests when GPRS-IMS-Bundled authentication is used for registration, reregistration and de-registration procedures, all REGISTER requests from the UE use the temporary IMPU as the public user identity even when the implicitly registered IMPUs are available at the UE. The UE does not use the temporary public user identity in any non-registration SIP requests.
On receiving the 200 (OK) response to the REGISTER request defined in subclause 5.1.1.2.1, there are no additional requirements for the UE.
NOTE 2: When GPRS-IMS-Bundled authentication is in use, a 401 (Unauthorized) response to the REGISTER request is not expected to be received. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.3 Subscription to the registration-state event package | Upon receipt of a 2xx response to the initial registration, the UE shall subscribe to the reg event package for the public user identity registered at the user's registrar (S-CSCF) as described in RFC 3680 [43] and RFC 6665 [28].
NOTE 1: If the UE supports RFC 6140 [191] and performs the functions of an external attached network, the subscription will be directed to the main URI, as described in RFC 6140 [191].
The UE shall subscribe to the reg event package upon registering a new contact address via an initial registration procedure. If the UE receives a NOTIFY request via the newly established subscription dialog and via the previously established subscription dialogs (there will be at least one), the UE may terminate the previously established subscription dialogs and keep only the newly established subscription dialog.
The UE shall use the default public user identity for subscription to the registration-state event package.
NOTE 2: The subscription information stored in the HSS ensures that the default public user identity is a SIP URI.
On sending a SUBSCRIBE request, the UE shall populate the header fields as follows:
a) a Request-URI set to the resource to which the UE wants to be subscribed to, i.e. to the SIP URI that is the default public user identity used for subscription;
b) a From header field set to the SIP URI that is the default public user identity used for subscription;
c) a To header field set to the SIP URI that is the default public user identity used for subscription;
d) an Event header field set to the "reg" event package;
e) an Expires header field set to 600 000 seconds as the value desired for the duration of the subscription;
f) void; and
g) void.
Upon receipt of a dialog establishing NOTIFY request, as specified in RFC 6665 [28], associated with the SUBSCRIBE request, the UE shall:
1) store the information for the established dialog;
2) store the expiration time as indicated in the "expires" header field parameter of the Subscription-State header field, if present, of the NOTIFY request. Otherwise the expiration time is retrieved from the Expires header field of the 2xx response to SUBSCRIBE request; and
3) follow the procedures specified in RFC 6665 [28].
If continued subscription is required, the UE shall automatically refresh the subscription to the reg event package, for a previously registered public user identity, either 600 seconds before the expiration time if the initial subscription was for greater than 1200 seconds, or when half of the time has expired if the initial subscription was for 1200 seconds or less. If a SUBSCRIBE request to refresh a subscription fails with a non-481 response, the UE shall still consider the original subscription valid for the duration of the most recently known "Expires" value according to RFC 6665 [28]. Otherwise, the UE shall consider the subscription invalid and start a new initial subscription according to RFC 6665 [28].
5.1.1.3A Void |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.4 User-initiated reregistration and registration of an additional public user identity | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.4.1 General | The UE can perform the reregistration of a previously registered public user identity bound to any one of its contact addresses and the associated set of security associations or TLS sessions at any time after the initial registration has been completed.
The UE can perform the reregistration of a previously registered public user identity over any existing set of security associations or TLS session that is associated with the related contact address.
The UE can perform the reregistration of a previously registered public user identity via an initial registration as specified in subclause 5.1.1.2, when binding the previously registered public user identity to new contact address or to the registration flow and the associated contact address (if the multiple registration mechanism is used).
The UE can perform registration of additional public user identities at any time after the initial registration has been completed. The UE shall perform the registration of additional public user identities either:
- over the existing set of security associations or TLS sessions, if appropriate to the security mechanism in use, that is associated with the related contact address; or
- via an initial registration as specified in subclause 5.1.1.2.
The UE can fetch bindings as defined in RFC 3261 [26] at any time after the initial registration has been completed. The procedure for fetching bindings is the same as for a reregistration except that the REGISTER request does not contain a Contact header field.
Unless either the user or the application within the UE has determined that a continued registration is not required the UE shall reregister an already registered public user identity either 600 seconds before the expiration time if the previous registration was for greater than 1200 seconds, or when half of the time has expired if the previous registration was for 1200 seconds or less, or when the UE intends to update its capabilities according to RFC 3840 [62] and RFC 5688 [120] or when the UE needs to modify the ICSI values that the UE intends to use in a g.3gpp.icsi-ref media feature tag or IARI values that the UE intends to use in the g.3gpp.iari-ref media feature tag.
When sending a protected REGISTER request, the UE shall use a security association or TLS session associated either with the contact address or with the registration flow and the associated contact address used to send the request, see 3GPP TS 33.203 [19], established as a result of an earlier initial registration.
The UE shall extract or derive a public user identity, the private user identity, and the domain name to be used in the Request-URI in the registration, according to the procedures described in subclause 5.1.1.1A or subclause 5.1.1.1B.
On sending a REGISTER request that does not contain a challenge response, the UE shall populate the header fields as follows:
a) a From header field set to the SIP URI that contains:
1) if the UE supports RFC 6140 [191] and performs the functions of an external attached network, the main URI of the UE; else
2) the public user identity to be registered;
b) a To header field set to the SIP URI that contains:
1) if the UE supports RFC 6140 [191] and performs the functions of an external attached network, the main URI of the UE; else
2) the public user identity to be registered;
c) a Contact header field set to include SIP URI(s) that contain(s) in the hostport parameter the IP address or FQDN of the UE, and containing the instance ID of the UE in the "+sip.instance" header field parameter, if the UE:
1) supports GRUU (see table A.4, item A.4/53);
2) supports multiple registrations;
3) has an IMEI available; or
4) has an MEID available.
Only the IMEI shall be used for generating an instance ID for a multi-mode UE that supports both 3GPP and 3GPP2 defined radio access networks.
NOTE 1: The requirement placed on the UE to include an instance ID based on the IMEI or the MEID when the UE does not support GRUU and does not support multiple registrations does not imply any additional requirements on the network.
If the UE support multiple registrations, it shall include "reg-id" header field as described in RFC 5626 [92]. The UE shall include all supported ICSI values (coded as specified in subclause 7.2A.8.2) in a g.3gpp.icsi-ref media feature tag as defined in subclause 7.9.2 and RFC 3840 [62] for the IMS communication it intends to use, and IARI values (coded as specified in subclause 7.2A.9.2), for the IMS applications it intends to use in a g.3gpp.iari-ref media feature tag as defined in subclause 7.9.3 and RFC 3840 [62].
If the UE supports RFC 6140 [191] and performs the functions of an external attached network, for the registration of bulk number contacts the UE shall include a Contact URI without a user portion and containing the "bnc" URI parameter.
If a user part has previously been included in an initial REGISTER request, the UE shall use the user part which was previously used to create the binding being refreshed or removed;
d) a Via header field set to include the IP address or FQDN of the UE in the sent-by field. For the TCP, the response is received on the TCP connection on which the request was sent. If the UE previously has previously negotiated sending of keep-alives associated with the registration, it shall include a "keep" header field parameter with no value in the Via header field, in order to indicate continuous support to send keep-alives, as described in RFC 6223 [143];
e) a registration expiration interval value, set to 600 000 seconds as the value desired for the duration of the registration;
NOTE 2: The registrar (S-CSCF) might decrease the duration of the registration in accordance with network policy. Registration attempts with a registration period of less than a predefined minimum value defined in the registrar will be rejected with a 423 (Interval Too Brief) response.
f) a Request-URI set to the SIP URI of the domain name of the home network used to address the REGISTER request;
g) the Supported header field containing the option-tag "path", and:
1) if GRUU is supported, the option-tag "gruu"; and
2) if multiple registrations is supported, the option-tag "outbound";
h) if available to the UE (as defined in the access technology specific annexes for each access technology), a P-Access-Network-Info header field set as specified for the access network technology (see subclause 7.2A.4);
i) a Security-Client header field to announce the media plane security mechanisms the UE supports, if any, labelled with the "mediasec" header field parameter specified in subclause 7.2A.7;
NOTE 3: The "mediasec" header field parameter indicates that security mechanisms are specific to the media plane.
j) if the UE supports RFC 6140 [191] and performs the functions of an external attached network, for the registration of bulk number contacts the UE shall include a Require header field containing the option-tag "gin"; and
k) if the UE supports RFC 6140 [191] and performs the functions of an external attached network, for the registration of bulk number contacts the UE shall include a Proxy-Require header field containing the option-tag "gin".
On receiving the 200 (OK) response to the REGISTER request, the UE shall:
a) bind the new expiration time of the registration for this public user identity found in the To header field value either to the contact address or to the registration flow and the associated contact address used in this registration;
NOTE 4: If the UE supports RFC 6140 [191] and performs the functions of an external attached network, the To header field will contain the main URI of the UE.
b) store the list of service route values contained in the Service-Route header field and bind the list either to the contact address or to the registration flow and the associated contact address (if the multiple registration mechanism is used);
NOTE 5: The stored list of service route values will be used to build a proper preloaded Route header field for new dialogs and standalone transactions (other than REGISTER method) when using either the respective contact address or the registration flow and the associated contact address (if the multiple registration mechanism is used).
NOTE 6: If the list of Service-Route headers saved from a previous registration and bound either to this contact address or to the registration flow and the associated contact address (if the multiple registration mechanism is used), and the associated set of security associations or TLS session already exist, then the received list of Service-Route headers replaces the old list.
NOTE 7: The UE can utilize additional URIs contained in the P-Associated-URI header field, e.g. for application purposes.
c) if the UE indicated support for GRUU in the Supported header field of the REGISTER request then:
- if the UE did not use the procedures specified in RFC 6140 [191] for registration find the Contact header field within the response that matches the one included in the REGISTER request. If this contains a "pub-gruu" header field parameter or a "temp-gruu" header field parameter or both, then store the value of those parameters as the GRUUs for the UE in association with the public user identity and the contact address that was registered; and
- if the UE used the procedures specified in RFC 6140 [191]for registration then find the Contact header field within the response that matches the one included in the REGISTER request. If this contains a "pub-gruu" header field parameter then store the value of the "pub-gruu" header field parameter for use for generating public GRUUs for registering UAs as specified in RFC 6140 [191]. If this contains a "temp-gruu-cookie" header field parameter then store the value of the "temp-gruu-cookie" header field parameter for use for generating temporary GRUUs for registering UAs as specified in RFC 6140 [191];
NOTE 8: When allocating public GRUUs to registering UAs the functionality within the UE that performs the role of registrar will add an "sg" SIP URI parameter that uniquenly identifies that UA to the public GRUU it received in the "pub-gruu" header field parameter. The procedures for generating a temporary GRUU using the "temp-gruu-cookie" header field parameter are specified in subclause 7.1.2.2 of RFC 6140 [191].
d) store the announcement of the media plane security mechanisms the P-CSCF (IMS-ALG) supports received in the Security-Server header field and labelled with the "mediasec" header field parameter specified in subclause 7.2A.7, if any. Once the UE chooses a media security mechanism from the list received in the Security-Server header field from the server, it may initiate that mechanism on a media level when it initiates new media in an existing session;
NOTE 9: The "mediasec" header field parameter indicates that security mechanisms are specific to the media plane.
e) if the Via header field contains a "keep" header field parameter with a value, continue to send keep-alives as described in RFC 6223 [143], towards the P-CSCF;
f) if the 200 (OK) response contains the Authentication-Info header field including a nextnonce field, store the contained nonce as a nonce for authentication associated to the same registration or registration flow (if the multiple registration mechanism is used) and shall delete any other previously stored nonce value for authentication for this registration or registration flow (if the multiple registration mechanism is used); and
NOTE 10: The related registration flow or registration is identified by the couple instance-id and reg-id if the multiple registration mechanism is used or by contact address if not.
g) if a Feature-Caps header field is received, a UE supporting the Feature-Caps header field shall consider the ICSI values received in the Feature-Caps header field of 200 (OK) response as supported for the established registration or registration flow (if the multiple registration mechanism is used) according to RFC 6809 [190]; and
NOTE 11: The UE and related applications can use the ICSI values received in the Feature-Caps header field to improve the user experience.
h) void.
When a 401 (Unauthorized) response to a REGISTER is received the UE shall behave as described in subclause 5.1.1.5.1.
On receiving a 423 (Interval Too Brief) response to the REGISTER request, the UE shall:
- send another REGISTER request populating the registration expiration interval value with an expiration timer of at least the value received in the Min-Expires header field of the 423 (Interval Too Brief) response.
On receiving a 408 (Request Timeout) response or 500 (Server Internal Error) response or 504 (Server Time-Out) response or 403 (Forbidden) response for a reregistration, the UE shall perform the procedures for initial registration as described in subclause 5.1.1.2.
On receiving a 305 (Use Proxy) response to the REGISTER request, unless otherwise specified in the access specific annexes (as described in annex B, annex L or annex U), the UE shall:
a) ignore the contents of the Contact header field if it is included in the received message;
NOTE 12: The 305 response is not expected to contain a Contact header field.
b) release all IP-CAN bearers used for the transport of media according to the procedures in subclause 9.2.2;
c) initiate either a new P-CSCF discovery procedure as described in subclause 9.2.1, or select a new P-CSCF, if the UE was pre-configured with more than one P-CSCF's IP addresses or domain names;
d) select a P-CSCF address, which is different from the previously used address, from the address list; and
e) perform the procedures for initial registration as described in subclause 5.1.1.2.
When the timer F expires at the UE:
1) the UE shall stop processing of all ongoing dialogs and transactions associated with that flow, if any (i.e. no further SIP signalling will be sent by the UE on behalf of these transactions or dialogs); and
2) after releasing all IP-CAN bearers used for the transport of media according to the procedures in subclause 9.2.2:
a) the UE may select a different P-CSCF address from the list of P-CSCF addresses discovered during the procedures described in subclause 9.2.1 or from its pre-configured list of P-CSCF's IP addresses or domain names;
b) if no response has been received when attempting to contact all P-CSCFs known by the UE, the UE may get a new set of P-CSCF-addresses as described in subclause 9.2.1 unless otherwise specified in the access specific annexes (as described in annex B, annex L or annex U);
c) the UE may perform the procedures for initial registration as described in subclause 5.1.1.2; and
d) the UE shall perform the procedures in RFC 5626 [92] to form a new flow to replace the failed one if it supports multiple registrations. If failed registration attempts occur in the process of creating a new flow, the UE shall implement the flow recovery procedures defined in subclause 4.5 of RFC 5626 [92] for determination of the retry delay time before each new registration attempt. The UE shall use the values of the parameters max-time and base-time, of the algorithm defined in subclause 4.5 of RFC 5626 [92]. If no values of the parameters max-time and base-time (if all failed) have been provided to the UE by the network, the default values defined in subclause 4.5 of RFC 5626 [92] shall be used.
NOTE 13: It is an implementation option whether these actions are also triggered by other means than expiration of timer F, e.g. based on ICMP messages.
On receiving a 503 response with a Retry-After header field to the REGISTER request and the Retry-After header field indicates time bigger than the value for timer F as specified in table 7.7.1, the UE:
a) may mark the currently used P-CSCF address as unavailable for the time indicated by the Retry-After header field;
b) if there is a locally stored P-CSCF address as specified in subclause 5.1.9 which is different from the currently used P-CSCF address and which is not marked as unavailable, may initiate an initial registration as specified in subclause 5.1.1.2 using that P-CSCF; and
c) if there is no locally stored P-CSCF address as specified in subclause 5.1.9 which is different from the currently used P-CSCF address and which is not marked as unavailable, may get a new set of P-CSCF addresses as described in subclause 9.2.1 unless otherwise specified in the access specific annexes (as described in annex B, annex L or annex U) and initiate an initial registration as specified in subclause 5.1.1.2.
NOTE 14: It is UE implementation dependent whether the UE stops processing of all ongoing dialogs and transactions associated with that flow.
On receiving a 503 response with a Retry-After header field to the REGISTER request and the Retry-After header field indicates time smaller than the value for timer F as specified in table 7.7.1, after the time indicated by the Retry-After header field elapses:
a) if the expiration time as indicated in the "expires" header field parameter of the Subscription-State header field or as retrieved from the Expires header field of the 2xx response to SUBSCRIBE request has not expired, the UE may attempt a reregistration to the same P-CSCF; or
b) if the expiration time as indicated in the "expires" header field parameter of the Subscription-State header field or as retrieved from the Expires header field of the 2xx response to SUBSCRIBE request has expired, the UE may attempt an initial registration as specified in subclause 5.1.1.2.
NOTE 15: When the expiration time has expied and the time indicated by the Retry-After header field does not elapse, the UE considers the subscription invalid.
NOTE 16: It is UE implementation dependent whether the UE sends reregistration due to RAT change or feature tag which includes the ICSI values that the UE intends to use in a g.3gpp.icsi-ref media feature tag or IARI values that the UE intends to use in the g.3gpp.iari-ref media feature tag during the time indicated by the Retry-After header field. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.4.2 IMS AKA as a security mechanism | On sending a REGISTER request, as defined in subclause 5.1.1.4.1, the UE shall additionally populate the header fields as follows:
a) an Authorization header field, with:
- the "username" header field parameter set to the value of the private user identity;
- the "realm" header field parameter directive, set to the value as received in the "realm" WWW-Authenticate header field parameter;
- the "uri" header field parameter, set to the SIP URI of the domain name of the home network;
- the "nonce" header field parameter, set to last received nonce value; and
- the "response" header field parameter, set to the last calculated response value;
NOTE 1: If the UE specifies its FQDN in the hostport parameter in the Contact header field and in the sent-by field in the Via header field, then it has to ensure that the given FQDN will resolve (e.g., by reverse DNS lookup) to the IP address that is bound to the security association.
NOTE 2: The UE associates two ports, a protected client port and a protected server port, with each pair of security associations. For details on the selection of the protected port value see 3GPP TS 33.203 [19].
NOTE 3: If the UE is setting up an additional registration using procedures specified in RFC 5626 [92] and the UE accesses the network through 3GPP or 3GPP2 systems without any NAT, the flow is considered to be "logical flow".
b) additionally for the Contact header field, include the protected server port value in the hostport parameter;
c) additionally for the Via header field, for UDP, if the REGISTER request is protected by a security association, include the protected server port value in the sent-by field;
d) a Security-Client header field, set to specify the signalling plane security mechanism it supports, the IPsec layer algorithms for security and confidentiality protection it supports and the new parameter values needed for the setup of two new pairs of security associations. For further details see 3GPP TS 33.203 [19] and RFC 3329 [48]; and
e) a Security-Verify header field that contains the content of the Security-Server header field received in the 401 (Unauthorized) response of the last successful authentication.
On receiving the 200 (OK) response to the REGISTER request, the UE shall additionally:
a) set the security association lifetime associated with either this contact address or the registration flow and the associated contact address (if the multiple registration mechanism is used), and the associated set of security associations to the longest of either the previously existing security association lifetime, or the lifetime of the just completed registration plus 30 seconds.
NOTE 4: If the UE receives Authentication-Info, it will proceed as described in RFC 3310 [49] when AKAv1 is used or as described in RFC 4169 [227] when AKAv2 is used. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.4.3 SIP digest without TLS as a security mechanism | On sending a REGISTER request, as defined in subclause 5.1.1.4.1, the UE shall additionally populate the header fields as follows:
a) an Authorization header field as defined in RFC 7616 [286] and RFC 8760 [287], including:
- the "username" header field parameter, set to the value of the private user identity;
- the "realm" header field parameter, set to the domain name of the home network;
- the "uri" header field parameter, set to the SIP URI of the domain name of the home network;
- the "nonce" header field parameter, set to the stored nonce value for authentication for the related registration or registration flow (if the multiple registration mechanism is used); and
NOTE: The related registration flow or registration is identified by the couple instance-id and reg-id if the multiple registration mechanism is used or by contact address if not.
- the "response" header field parameter, set to the challenge response, constructed using the stored nonce value for authentication for the same registration or registration flow ( if the multiple registration mechanism is used), along with "algorithm", "cnonce", "qop", and "nc" header field parameters as specified in RFC 7616 [286] and RFC 8760 [287];
b) the Contact header field with the port value of an unprotected port where the UE expects to receive subsequent requests; and
c) the Via header field with the port value of an unprotected port where the UE expects to receive responses to the request. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.4.4 SIP digest with TLS as a security mechanism | On sending a REGISTER request, as defined in subclause 5.1.1.4.1, the UE shall additionally populate the header fields as follows:
a) an Authorization header field set in accordance with subclause 5.1.1.4.3;
b) the Security-Client header field set to specify the signalling plane security mechanism the UE supports. The UE shall support the setup of a TLS session as defined in 3GPP TS 33.203 [19]. The UE shall support the "tls" security mechanism, as specified in RFC 3329 [48]. The UE shall support TLS for integrity and confidentiality protection as defined in RFC 3261 [26], and shall announce support for them according to the procedures defined in RFC 3329 [48]; and
c) a Security-Verify header field that contains the content of the Security-Server header field received in the 401 (Unauthorized) response of the last successful authentication.
On receiving the 200 (OK) response to the REGISTER request defined in subclause 5.1.1.2.1, the UE shall additionally:
a) set the lifetime of the respective TLS session to the value configured. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.4.5 NASS-IMS bundled authentication as a security mechanism | On sending a REGISTER request, as defined in subclause 5.1.1.4.1, the UE shall additionally populate the header fields as follows:
a) optionally, an Authorization header field, with the "username" header field parameter, set to the value of the private user identity;
NOTE 1: In case the Authorization header field is absent, the mechanism only supports that one public user identity is associated with only one private user identity.
On receiving the 200 (OK) response to the REGISTER request defined in subclause 5.1.1.2.1, there are no additional requirements for the UE.
NOTE 2: When NASS-IMS bundled authentication is in use, a 401 (Unauthorized) response to the REGISTER request is not expected to be received. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.4.6 GPRS-IMS-Bundled authentication as a security mechanism | On sending a REGISTER request, as defined in subclause 5.1.1.4.1, the UE shall additionally populate the header fields as follows:
a) an Authorization header field as defined in RFC 7616 [286] and RFC 8760 [287] shall not be included, in order to indicate support GPRS-IMS-Bundled authentication.
b) security agreement header field values as required by RFC 3329 [48] shall not contain signalling plane security mechanisms;
c) a From header field set to a temporary public user identity derived from the IMSI, as defined in 3GPP TS 23.003 [3], as the public user identity to be registered;
d) a To header field set to a temporary public user identity derived from the IMSI, as defined in 3GPP TS 23.003 [3], as the public user identity to be registered;
e) the Contact header field with the port value of an unprotected port where the UE expects to receive subsequent mid-dialog requests; and
f) the Via header field with the port value of an unprotected port where the UE expects to receive responses to the request.
NOTE 1: Since the private user identity is not included in the REGISTER requests when GPRS-IMS-Bundled authentication is used for registration, reregistration and de-registration procedures, all REGISTER requests from the UE use the IMSI-derived IMPU as the public user identity even when the implicitly registered IMPUs are available at the UE. The UE does not use the temporary public user identity (IMSI-derived IMPU) in any non-registration SIP requests.
On receiving the 200 (OK) response to the REGISTER request defined in subclause 5.1.1.4.1, there are no additional requirements for the UE.
NOTE 2: When GPRS-IMS-Bundled authentication is in use, a 401 (Unauthorized) response to the REGISTER request is not expected to be received. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.5 Authentication | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.5.1 IMS AKA - general | Authentication is performed during initial registration. A UE can be re-authenticated during subsequent reregistrations, deregistrations or registrations of additional public user identities. When the network requires authentication or re-authentication of the UE, the UE will receive a 401 (Unauthorized) response to the REGISTER request.
On receiving a 401 (Unauthorized) response to the REGISTER request containing one or more WWW-Authenticate header fields the UE shall select the topmost header field that it supports (i.e. where the "algorithm" WWW-Authenticate header field parameter is "AKAv2-SHA-256" or "AKAv1-MD5"), the UE shall:
NOTE 1: The "AKAv1-MD5" algorithm is only supported for backward compatibility.
1) extract the RAND and AUTN parameters;
2) check the validity of a received authentication challenge, as described in 3GPP TS 33.203 [19] i.e. the locally calculated XMAC must match the MAC parameter derived from the AUTN part of the challenge; and the SQN parameter derived from the AUTN part of the challenge must be within the correct range; and
3) check the existence of the Security-Server header field as described in RFC 3329 [48]. If the Security-Server header field is not present or it does not contain the parameters required for the setup of the set of security associations (see annex H of 3GPP TS 33.203 [19]), the UE shall abandon the authentication procedure and send a new REGISTER request with a new Call-ID.
In the case that the 401 (Unauthorized) response to the REGISTER request is deemed to be valid the UE shall:
1) calculate the RES parameter and derive the keys CK and IK from RAND as described in 3GPP TS 33.203 [19];
2) set up a temporary set of security associations for this registration based on the static list and parameters the UE received in the 401 (Unauthorized) response and its capabilities sent in the Security-Client header field in the REGISTER request. The UE sets up the temporary set of security associations using the most preferred mechanism and algorithm returned by the P-CSCF and supported by the UE and using IK and CK (only if encryption enabled) as the shared key. The UE shall use the parameters received in the Security-Server header field to setup the temporary set of security associations. The UE shall set a temporary SIP level lifetime for the temporary set of security associations to the value of reg-await-auth timer;
3) store the announcement of the media plane security mechanisms the P-CSCF (IMS-ALG) supports received in the Security-Server header field and labelled with the "mediasec" header field parameter specified in subclause 7.2A.7, if any; and
NOTE 2: The "mediasec" header field parameter indicates that security mechanisms are specific to the media plane.
4) send another REGISTER request towards the protected server port indicated in the response using the temporary set of security associations to protect the message. The header fields are populated as defined for the initial REGISTER request that was challenged with the received 401 (Unauthorized) response, with the addition that the UE shall include an Authorization header field containing:
- the "realm" header field parameter set to the value as received in the "realm" WWW-Authenticate header field parameter;
- the "username" header field parameter, set to the value of the private user identity;
- the "response" header field parameter that contains the RES parameter, as described in RFC 3310 [49] when AKAv1 is used or as described in RFC 4169 [227] when AKAv2 is used;
- the "uri" header field parameter, set to the SIP URI of the domain name of the home network;
- the "algorithm" header field parameter, set to the value received in the 401 (Unauthorized) response; and
- the "nonce" header field parameter, set to the value received in the 401 (Unauthorized) response.
The UE shall also insert the Security-Client header field that is identical to the Security-Client header field that was included in the previous REGISTER request (i.e. the REGISTER request that was challenged with the received 401 (Unauthorized) response). The UE shall also insert the Security-Verify header field into the request, by mirroring in it the content of the Security-Server header field received in the 401 (Unauthorized) response. The UE shall set the Call-ID of the security association protected REGISTER request which carries the authentication challenge response to the same value as the Call-ID of the 401 (Unauthorized) response which carried the challenge.
NOTE 3: The Security-Client header field contains signalling plane security mechanism and if the UE supports media plane security, then media plane security mechanisms are contained, too.
On receiving the 200 (OK) response for the security association protected REGISTER request registering a public user identity with the associated contact address, the UE shall:
- change the temporary set of security associations to a newly established set of security associations, i.e. set its SIP level lifetime to the longest of either the previously existing set of security associations SIP level lifetime, or the lifetime of the just completed registration plus 30 seconds; and
- if this is the only set of security associations available toward the P-CSCF, use the newly established set of security associations for further messages sent towards the P-CSCF. If there are additional sets of security associations (e.g. due to registration of multiple contact addresses), the UE can either use them or use the newly established set of security associations for further messages sent towards the P-CSCF as appropriate.
NOTE 4: If the UE has registered multiple contact addresses, the UE can either send requests towards the P-CSCF over the newly established set of security associations, or use different UE's contact address and associated set of security associations when sending the requests towards the P-CSCF. Responses towards the P-CSCF that are sent via UDP will be sent over the same set of security associations that the related request was received on. Responses towards the P-CSCF that are sent via TCP will be sent over the same set of security associations that the related request was received on.
When the first request or response protected with the newly established set of security associations is received from the P-CSCF or when the lifetime of the old set of security associations expires, the UE shall delete the old set of security associations and related keys it may have with the P-CSCF after all SIP transactions that use the old set of security associations are completed.
NOTE 5: If the UE has registered multiple contact addresses, the S-CSCF can use different contact address when sending the requests destined for the UE. In this case the UE will not receive the subsequent requests over the newly established set of security associations.
Whenever the 200 (OK) response is not received before the temporary SIP level lifetime of the temporary set of security associations expires or a 403 (Forbidden) response is received, the UE shall consider the registration to have failed. The UE shall delete the temporary set of security associations it was trying to establish, and use the old set of security associations. The UE should send an unprotected REGISTER request according to the procedure specified in subclause 5.1.1.2 if the UE considers the old set of security associations to be no longer active at the P-CSCF.
In the case that the 401 (Unauthorized) response is deemed to be invalid then the UE shall behave as defined in subclause 5.1.1.5.3. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.5.2 Void | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.5.3 IMS AKA abnormal cases | If, in a 401 (Unauthorized) response, either the MAC or SQN is incorrect the UE shall respond with a further REGISTER indicating to the S-CSCF that the challenge has been deemed invalid as follows:
- in the case where the UE deems the MAC parameter to be invalid the subsequent REGISTER request shall contain no "auts" Authorization header field parameter and an empty "response" Authorization header field parameter, i.e. no authentication challenge response;
- in the case where the UE deems the SQN to be out of range, the subsequent REGISTER request shall contain the "auts" Authorization header field parameter (see 3GPP TS 33.102 [18]).
NOTE: In the case of the SQN being out of range, a "response" Authorization header field parameter can be included by the UE, based on the procedures described in RFC 3310 [49].
Whenever the UE detects any of the above cases, the UE shall:
- send the REGISTER request using an existing set of security associations, if available (see 3GPP TS 33.203 [19]);
- populate a new Security-Client header field within the REGISTER request and associated contact address, set to specify the security mechanisms it supports, the IPsec layer algorithms for integrity and confidentiality protection it supports and the parameters needed for the new security association setup. These parameters shall contain new values for spi_uc, spi_us and port_uc; and
- not create a temporary set of security associations.
On receiving a 420 (Bad Extension) in which the Unsupported header field contains the value "sec-agree" and if the UE supports GPRS-IMS-Bundled authentication, the UE shall initiate a new authentication attempt with the GPRS-IMS-Bundled authentication procedures as specified in subclause 5.1.1.2.6. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.5.4 SIP digest without TLS – general | On receiving a 401 (Unauthorized) response to the REGISTER request containing one or more WWW-Authenticate header fields the UE shall select the topmost header field that it supports (i.e. where the "algorithm" WWW-Authenticate header field parameter is "SHA-256", "SHA-512-256" or "MD5"), and the UE shall:
NOTE 1: The MD5 algorithm is only supported for backward compatibility.
1) extract the digest-challenge parameters as indicated in RFC 7616 [286] and RFC 8760 [287] from the WWW-Authenticate header field;
2) store the contained nonce value as the nonce for authentication associated to the same registration or registration flow (if the multiple registration mechanism is used) and delete any other previously stored nonce value for authentication for this registration or registration flow (if the multiple registration mechanism is used);
NOTE 2: The related registration flow or registration is identified by the couple instance-id and reg-id if the multiple registration mechanism is used or by contact address if not.
3) calculate digest-response parameters as indicated in RFC 7616 [286] and RFC 8760 [287];
4) send another REGISTER request containing an Authorization header field. The header fields are populated as defined in subclause 5.1.1.2.3, with the addition that the UE shall include an Authorization header field containing a challenge response, constructed using the stored nonce value for authentication for the same registration or registration flow (if the multiple registration mechanism is used) , "algorithm", "cnonce", "qop", and "nc" header field parameters as indicated in RFC 7616 [286] and RFC 8760 [287]. The UE shall set the Call-ID of the REGISTER request which carries the authentication challenge response to the same value as the Call-ID of the 401 (Unauthorized) response which carried the challenge. If SIP digest without TLS is used, the UE shall not include RFC 3329 [48] header fields with this REGISTER.
On receiving the 200 (OK) response for the REGISTER request, if the "algorithm" Authentication-Info header field parameter is "SHA-256", "SHA-512-256" or "MD5", the UE shall authenticate the S-CSCF using the "rspauth" Authentication-Info header field parameter as described in RFC 7616 [286] and RFC 8760 [287]. If the nextnonce field is present in the Authentication-Info header field the UE shall store the contained nonce value as the nonce for authentication associated to the same registration or registration flow (if the multiple registration mechanism is used) and shall delete any other previously stored nonce value for authentication for this registration or registration flow (if the multiple registration mechanism is used). |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.5.5 SIP digest without TLS – abnormal procedures | On receiving a 403 (Forbidden) response, the UE shall consider the registration to have failed. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.5.6 SIP digest with TLS – general | On receiving a 401 (Unauthorized) response to the REGISTER request, the procedures in subclause 5.1.1.5.4 apply with the following differences:
- The UE shall check the existence of the Security-Server header field as described in RFC 3329 [48]. If the Security-Server header field is not present or the list of supported security mechanisms does not include "tls", the UE shall abandon the authentication procedure and send a new REGISTER request.
In the case that the 401 (Unauthorized) response to the REGISTER is deemed to be valid the UE shall:
- store the announcement of the media plane security mechanisms the P-CSCF (IMS-ALG) supports labelled with the "mediasec" header field parameter specified in subclause 7.2A.7 and received in the Security-Server header field, if any; and
NOTE 1: The "mediasec" header field parameter indicates that security mechanisms are specific to the media plane.
- send another REGISTER request using the TLS session to protect the message.
The header fields are populated as defined for the initial request, with the addition that the UE shall include an Authorization header field containing a challenge response, constructed using the stored nonce value for authentication for the same registration or registration flow (if the multiple registration mechanism is used), "algorithm", "cnonce", "qop", and "nc" header field parameters as indicated in RFC 7616 [286] and RFC 8760 [287]. The UE shall also insert the Security-Client header field that is identical to the Security-Client header field that was included in the previous REGISTER request (i.e. the REGISTER request that was challenged with the received 401 (Unauthorized) response). The UE shall also insert the Security-Verify header field into the request, by mirroring in it the content of the Security-Server header field received in the 401 (Unauthorized) response. The UE shall set the Call-ID to the same value as the Call-ID of the 401 (Unauthorized) response which carried the challenge.
NOTE 2: The Security-Client header field contains signalling plane security mechanism and if the UE supports media plane security, then media plane security mechanisms are contained, too.
When SIP digest with TLS is used, and for the case where the 401 (Unauthorized) response to the REGISTER request is deemed to be valid, the UE shall establish the TLS session as described in 3GPP TS 33.203 [19]. The UE shall use this TLS session to send all further messages towards the P-CSCF towards the protected server port.
NOTE 3: The related registration flow or registration is identified by the couple instance-id and reg-id if the multiple registration mechanism is used or by contact address if not. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.5.7 SIP digest with TLS – abnormal procedures | On receiving a 403 (Forbidden) response, the UE shall consider the registration to have failed. If performing SIP digest with TLS, the UE should send an initial REGISTER according to the procedure specified in subclause 5.1.1.2 if the UE considers the TLS session to be no longer active at the P-CSCF. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.5.8 NASS-IMS bundled authentication – general | NASS-IMS bundled authentication is only applicable to UEs that contain neither USIM nor ISIM. Authentication is achieved via the registration and reregistration procedures as defined in subclause 5.1.1.2 and subclause 5.1.1.4. NASS-bundled authentication is granted by the network upon receipt by the UE of a 200 (OK) response to the initial REGISTER request.
There is no separate authentication procedure. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.5.9 NASS-IMS bundled authentication – abnormal procedures | There is no separate authentication procedure, and therefore no abnormal procedures. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.5.10 GPRS-IMS-Bundled authentication – general | Authentication is achieved via the registration and reregistration procedures as defined in subclause 5.1.1.2 and subclause 5.1.1.4. GPRS-IMS-Bundled authentication is granted by the network upon receipt by the UE of a 200 (OK) response to the initial REGISTER request. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.5.11 GPRS-IMS-Bundled authentication – abnormal procedures | There is no separate authentication procedure and therefore no abnormal procedures. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.5.12 Abnormal procedures for all security mechanisms | A UE shall only respond to two consecutive invalid challenges. The UE may attempt to register with the network again after an implementation specific time.
5.1.1.5A Network-initiated re-authentication
At any time, the UE can receive a NOTIFY request carrying information related to the reg event package (as described in subclause 5.1.1.3). If:
- the state attribute in any of the <registration> elements is set to "active";
- the value of the <uri> sub-element inside the <contact> sub-element is set to the Contact address that the UE registered; and
- the event attribute of that <contact> sub-element(s) is set to "shortened";
the UE shall:
1) use the expires attribute of the <contact> sub-element that the UE registered to adjust the expiration time for that public user identity; and
2) start the re-authentication procedures at the appropriate time (as a result of the S-CSCF procedure described in subclause 5.4.1.6) by initiating a reregistration as described in subclause 5.1.1.4, if required.
NOTE: When authenticating a given private user identity, the S-CSCF will only shorten the expiry time within the <contact> sub-element that the UE registered using its private user identity. The <contact> elements for the same public user identity, if registered by another UE using different private user identities remain unchanged. The UE will not initiate a reregistration procedure, if none of its <contact> sub-elements was modified.
5.1.1.5B Change of IPv6 address due to privacy
Stateless address autoconfiguration as described in RFC 2462 [20E] defines how an IPv6 prefix and an interface identifier is used by the UE to construct a complete IPv6 address.
If the UE receives an IPv6 prefix, the UE may change the interface identity of the IPv6 address as described in RFC 8981 [293] due to privacy but this can result in service discontinuity for services provided by the IM CN subsystem.
NOTE: When the UE constructs new IPv6 address by changing the interface identity, the UE can either transfer all established dialogs to new IPv6 address as specified in 3GPP TS 24.237 [8M] and subsequently relinquish the old IPv6 address, or terminate all established dialogs and transactions. While transferring the established dialogs to new IPv6 address, the UE will have double registration, i.e. one registration for the old IPv6 address and another for the new IPv6 address.
The procedure described below assumes that the UE will terminate all established dialogs and transactions and temporarily disconnect the UE from the IM CN subsystem until the new registration is performed. If the UE decides to change the IPv6 address due to privacy and terminate all established dialogs and transaction, associated with old IPv6 address, the UE shall:
1) terminate all ongoing dialogs (e.g., sessions) and transactions (e.g., subscription to the reg event) that were using the old IPv6 address;
2) deregister all registered public user identities that were using the old IPv6 address as described in subsclause 5.1.1.4;
3) construct a new IPv6 address according to the procedures specified in RFC 8981 [293];
4) register the public user identities that were deregistered in step 2 above with a new IPv6 address, as follows:
a) by performing an initial registration as described in subsclause 5.1.1.2; and
b) by performing a subscription to the reg event package as described in subsclause 5.1.1.3; and
5) subscribe to other event packages it was subscribed to before the change of IPv6 address procedure started.
To ensure a maximum degree of continuous service to the end user, the UE should transfer all established dialogs to the new IPv6 address as specified in 3GPP TS 24.237 [8M] rather than terminate all established dialogs and transactions and temporarily disconnect the UE from the IM CN subsystem as described above. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.6 User-initiated deregistration | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.6.1 General | For any public user identity that the UE has previously registered, the UE can deregister via a single registration procedure:
- all contact addresses bound to the indicated public user identity;
- some contact addresses bound to the indicated public user identity;
- a particular contact address bound to the indicated public user identity; or
- when the UE supports multiple registrations (i.e. the "outbound" option tag is included in the Supported header field) one or more flows bound to the indicated public user identity.
The UE can deregister a public user identity that it has previously registered with its contact address at any time. The UE shall protect the REGISTER request using a security association or TLS session that is associated with contact address, see 3GPP TS 33.203 [19], established as a result of an earlier registration, if one is available.
The UE shall extract or derive a public user identity, the private user identity, and the domain name to be used in the Request-URI in the registration, according to the procedures described in subclause 5.1.1.1A or subclause 5.1.1.1B.
Prior to sending a REGISTER request for deregistration, the UE shall release all dialogs that were using the contact addresses or the flow that is going to be deregistered and related to the public user identity that is going to be deregistered or to one of the implicitly registered public user identities. However:
- if the dialog that was established by the UE subscribing to the reg event package used the public user identity that is going to be deregistered; and
- this dialog is the only remaining dialog used for subscription to reg event package of the user, i.e. there are no other contact addresses registered with associated subscription to the reg event package of the user;
then the UE shall not release this dialog.
On sending a REGISTER request that will remove the binding between the public user identity and one of its contact addresses or one of its flows, the UE shall populate the header fields as follows:
a) a From header field set to the SIP URI that contains:
1) if the UE supports RFC 6140 [191] and performs the functions of an external attached network, the main URI of the UE; else
2) the public user identity to be deregistered;
b) a To header field set to the SIP URI that contains:
1) if the UE supports RFC 6140 [191] and performs the functions of an external attached network, the main URI of the UE; else
2) the public user identity to be deregistered;
c) a Contact header field set to the SIP URI(s) that contain(s) in the hostport parameter the IP address of the UE or FQDN, and:
1) if the UE is removing the binding between the public user identity indicated in the To header field, (together with the associated implicitly registered public user identities), and the contact address indicated in the Contact header field; and
- if the UE supports GRUU, or multiple registrations (i.e. the "outbound" option tag is included in the Supported header field), or has an IMEI available, or has an MEID available, the Contact header field also contains the "+sip.instance" header field parameter. Only the IMEI shall be used for generating an instance ID for a multi-mode UE that supports both 3GPP and 3GPP2 defined radio access networks;
- if the UE supports multiple registrations (i.e. the "outbound" option tag is included in the Supported header field), the Contact header field does not contain the "reg-id" header field parameter;
- if the UE does not supports GRUU and does not support multiple registrations (i.e. the "outbound" option tag is not included in the Supported header field), and does not have an IMEI available, and does not have an MEID available, the Contact header field does not contain either the "+sip.instance" header field parameter or the "reg-id" header field parameter;
NOTE 1: Since the contact address is deregistered, if there are any flows that were previously registered with the respective contact address, all flows terminating at the respective contact address are removed.
2) if the UE is removing the binding between the public user identity indicated in the To header field, (together with the associated implicitly registered public user identities) and one of its flows, the Contact header field contains the "+sip.instance" header field parameter and the "reg-id" header field parameter that identifies the flow; and
NOTE 2: The requirement placed on the UE to include an instance ID based on the IMEI when the UE does not support GRUU and does not support multiple registrations does not imply any additional requirements on the network.
3) if the UE supports RFC 6140 [191] and performs the functions of an external attached network, for the registration of bulk number contacts the UE shall include a Contact URI without a user portion and containing the "bnc" URI parameter;
d) a Via header field set to include the IP address or FQDN of the UE in the sent-by field;
e) a registration expiration interval value set to the value of zero, appropriate to the deregistration requirements of the user;
f) a Request-URI set to the SIP URI of the domain name of the home network used to address the REGISTER request;
g) if available to the UE (as defined in the access technology specific annexes for each access technology), a P-Access-Network-Info header field set as specified for the access network technology (see subclause 7.2A.4);
h) a Security-Client header field to announce the media plane security mechanisms the UE supports, if any;
NOTE 3: The "mediasec" header field parameter indicates that security mechanisms are specific to the media plane.
i) if the UE supports RFC 6140 [191] and performs the functions of an external attached network, for the registration of bulk number contacts the UE shall include a Require header field containing the option-tag "gin"; and
j) if the UE supports RFC 6140 [191] and performs the functions of an external attached network, for the registration of bulk number contacts the UE shall include a Proxy-Require header field containing the option-tag "gin".
For a public user identity that the UE has registered with multiple contact addresses or multiple flows (e.g. via different P-CSCFs), the UE shall also be able to deregister multiple contact addresses or multiple flows, bound to its public user identity, via single deregistration proceduere as specified in RFC 3261 [26]. The UE shall send a single REGISTER request, using one of its contact addresses and the associated set of security associations or TLS session, containing a list of Contact headers. Each Contact header field is populated as specifed above in bullets a) through i).
The UE can deregister all contact addresses bound to its public user identity and associated with its private user identity. The UE shall send a single REGISTER request, using one of its contact addresses and the associated set of security associations or TLS session, containing a public user identity that is being deregistered in the To header field, and a single Contact header field with value of "*" and the Expires header field with a value of "0". The UE shall not include the "instance-id" feature tag and the "reg-id" header field parameter in the Contact header field in the REGISTER request.
NOTE 4: All entities subscribed to the reg event package of the user will be informed via NOTIFY request which contact addresses bound to the public user identity have been deregistered.
When a 401 (Unauthorized) response to a REGISTER request is received the UE shall behave as described in subclause 5.1.1.5.1.
On receiving the 200 (OK) response to the REGISTER request, the UE shall:
- remove all registration details relating to this public user identity and the associated contact address.
- store the announcement of the media plane security mechanisms the P-CSCF (IMS-ALG) supports labelled with the "mediasec" header field parameter specified in subclause 7.2A.7 and received in the Security-Server header field, if any.
NOTE 5: The "mediasec" header field parameter indicates that security mechanisms are specific to the media plane.
If there are no more public user identities registered with this contact address, the UE shall delete any stored media plane security mechanisms and related keys and any security associations or TLS sessions and related keys it may have towards the IM CN subsystem.
If all public user identities are deregistered and all security association or TLS session is removed, then the UE shall consider subscription to the reg event package cancelled (i.e. as if the UE had sent a SUBSCRIBE request with an Expires header field containing a value of zero). |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.6.2 IMS AKA as a security mechanism | On sending a REGISTER request, as defined in subclause 5.1.1.6.1, the UE shall additionally populate the header fields as follows:
a) an Authorization header field, with:
- the "username" header field parameter, set to the value of the private user identity;
- the "realm" header field parameter, set to the value as received in the "realm" WWW-Authenticate header field parameter;
- the "uri" header field parameter, set to the SIP URI of the domain name of the home network;
- the "nonce" header field parameter, set to last received nonce value; and
- the response directive, set to the last calculated response value;
b) additionally for each Contact header field and associated contact address, include the associated protected server port value in the hostport parameter;
c) additionally for the Via header field, include the protected server port value bound to the security association in the sent-by field;
NOTE 1: If the UE specifies its FQDN in the hostport parameter in the Contact header field and in the sent-by field in the Via header field, then it has to ensure that the given FQDN will resolve (e.g., by reverse DNS lookup) to the IP address that is bound to the security association.
d) a Security-Client header field, set to specify the signalling plane security mechanisms it supports, the IPsec layer algorithms for integrity and confidentiality protection it supports and the new parameter values needed for the setup of two new pairs of security associations. For further details see 3GPP TS 33.203 [19] and RFC 3329 [48]; and
e) a Security-Verify header field that contains the content of the Security-Server header field received in the 401 (Unauthorized) response of the last successful authentication.
NOTE 2: When the UE has received the 200 (OK) response for the REGISTER request of the only public user identity currently registered with this contact address and its associated set of implicitly registered public user identities (i.e. no other public user identity is registered), the UE removes the security association (between the P-CSCF and the UE) that were using this contact address. Therefore further SIP signalling using this security association (e.g. the NOTIFY request containing the deregistration event) will not reach the UE. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.6.3 SIP digest without TLS as a security mechanism | On sending a REGISTER request, as defined in subclause 5.1.1.6.1, the UE shall additionally populate the header fields as follows:
a) an Authorization header field as defined in RFC 7616 [286] and RFC 8760 [287], including:
- the "username" header field parameter, set to the value of the private user identity;
- the "realm" header field parameter, set to the domain name of the home network;
- the "uri" header field parameter, set to the SIP URI of the domain name of the home network;
- the "nonce" header field parameter, set to an empty value; and
- the "response" header field parameter, set to an empty value;
b) for each Contact header field and associated contact address include the associated unprotected port value (where the UE was expecting to receive mid-dialog requests); and
c) the Via header field with the port value of an unprotected port where the UE expects to receive responses to the request. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.6.4 SIP digest with TLS as a security mechanism | On sending a REGISTER request, as defined in subclause 5.1.1.6.1, the UE shall additionally populate the header fields as follows:
a) an Authorization header field set in accordance with subclause 5.1.1.6.3; and
b) a Security-Client header field, set to specify the signalling plane security mechanism it supports. For further details see 3GPP TS 33.203 [19] and RFC 3329 [48]; and
c) a Security-Verify header field that contains the content of the Security-Server header field received in the 401 (Unauthorized) response of the last successful authentication. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.6.5 NASS-IMS bundled authentication as a security mechanism | On sending a REGISTER request, as defined in subclause 5.1.1.6.1, the UE shall additionally populate the header fields as follows:
a) optionally, an Authorization header field, with the "username" header field parameter, set to the value of the private user identity;
NOTE 1: In case the Authorization header field is absent, the mechanism only supports that one public user identity is associated with only one private user identity.
On receiving the 200 (OK) response to the REGISTER request defined in subclause 5.1.1.6.1, there are no additional requirements for the UE.
NOTE 2: When NASS-IMS bundled authentication is in use, a 401 (Unauthorized) response to the REGISTER request is not expected to be received. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.6.6 GPRS-IMS-Bundled authentication as a security mechanism | On sending a REGISTER request, as defined in subclause 5.1.1.6.1, the UE shall additionally populate the header fields as follows:
a) an Authorization header field as defined in RFC 7616 [286] and RFC 8760 [287] shall not be included, in order to indicate support GPRS-IMS-Bundled authentication.
b) the Security-Verify header field and the Security-Client header field values as defined by RFC 3329 [48] shall not contain signalling plane security mechanisms;
c) a From header field set to a temporary public user identity derived from the IMSI, as defined in 3GPP TS 23.003 [3], as the public user identity to be deregistered;
d) a To header field set to a temporary public user identity derived from the IMSI, as defined in 3GPP TS 23.003 [3], as the public user identity to be deregistered;
e) for each Contact header field and associated contact address include the associated unprotected port value (where the UE was expecting to receive mid-dialog requests); and
f) the Via header field with the port value of an unprotected port where the UE expects to receive responses to the request.
NOTE 1: Since the private user identity is not included in the REGISTER requests when GPRS-IMS-Bundled authentication is used for registration, reregistration and de-registration procedures, all REGISTER requests from the UE use the IMSI-derived IMPU as the public user identity even when the implicitly registered IMPUs are available at the UE. The UE does not use the temporary public user identity (IMSI-derived IMPU) in any non-registration SIP requests.
On receiving the 200 (OK) response to the REGISTER request defined in subclause 5.1.1.6.1, there are no additional requirements for the UE.
NOTE 2: When GPRS-IMS-Bundled authentication is in use, a 401 (Unauthorized) response to the REGISTER request is not expected to be received. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.1.7 Network-initiated deregistration | Upon receipt of a NOTIFY request, on any dialog which was generated during the subscription to the reg event package as described in subclause 5.1.1.3, including one or more <registration> element(s) which were registered by this UE, with:
1) the state attribute within the <registration> element set to "terminated", and within each <contact> element belonging to this UE, the state attribute set to "terminated" and the event attribute set either to "unregistered", or "rejected", or "deactivated", the UE shall remove all registration details relating to the respective public user identity (i.e. consider the public user identity indicated in the aor attribute of the <registration> element as deregistered); or
2) the state attribute within the <registration> element set to "active", and within a given <contact> element belonging to this UE, the state attribute set to "terminated", and the associated event attribute set either to "unregistered", or "rejected" or "deactivated", the UE shall consider the binding between the public user identity and either the contact address or the registration flow and the associated contact address (if the multiple registration mechanism is used) indicated in the respective <contact> element as removed. The UE shall consider its public user identity as deregistered when all bindings between the respective public user identity and all contact addresses and all registration flow and the associated contact address (if the multiple registration mechanism is used) belonging to this UE are removed.
NOTE 1: When multiple registration mechanism is used to register a public user identity and bind it to a registration flow and the associated contact address, there will be one <contact> element for each registration flow and the associated contact address.
NOTE 2: If the state attribute within the <registration> element is set to "active" and the <contact> element belonging to this UE is set to "active", the UE will consider that the binding between the public user identity and either the respective contact address or the registration flow and the associated contact address as left unchanged.
In case of a "deactivated" event attribute, the UE shall start the initial registration procedure as described in subclause 5.1.1.2. In case of a "rejected" event attribute, the UE shall release all dialogs related to those public user identities.
Upon receipt of a NOTIFY request, the UE shall delete all security associations or TLS sessions towards the P-CSCF either:
- if all <registration> element(s) have their state attribute set to "terminated" (i.e. all public user identities are deregistered) and the Subscription-State header field contains the value of "terminated"; or
- if each <registration> element that was registered by this UE has either the state attribute set to "terminated", or the state attribute set to "active" and the state attribute within the <contact> element belonging to this UE set to "terminated".
When all UE's public user identities are registered via a single P-CSCF and the subscription dialog to the reg event package of the UE is set via the respective P-CSCF, the UE shall delete these security associations or TLS sessions towards the respective P-CSCF when all public user identities have been deregistered and after the server transaction (as defined in RFC 3261 [26]) pertaining to the received NOTIFY request terminates.
NOTE 3: Deleting a security association or TLS session is an internal procedure of the UE and does not involve any SIP procedures.
NOTE 4: If all the public user identities (i.e. <contact> elements) registered by this UE are deregistered and the security associations or TLS sessions have been removed, the UE considers the subscription to the reg event package terminated since the NOTIFY request was received with Subscription-State header field containing the value of "terminated". |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.2 Subscription and notification | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.2.1 Notification about multiple registered public user identities | Upon receipt of a NOTIFY request for the dialog associated with the subscription to the reg event package the UE shall perform the following actions:
- store the information for the established dialog;
- store the expiration time as indicated in the "expires" header field parameter of the Subscription-State header field, if present, of the NOTIFY request. Otherwise the expiration time is retrieved from the Expires header field of the 2xx response to SUBSCRIBE request;
- if a <registration> element with state attribute "active", i.e. registered, is received for one or more public user identities, the UE shall store the indicated public user identities as registered;
- if a <registration> element with state attribute "active" is received, and the UE supports GRUU (see table A.4, item A.4/53), then for each public user identity indicated in the notification that contains a <pub-gruu> element or a <temp-gruu> element or both (as defined in RFC 5628 [94]), the UE shall store the value of those elements in association with the public user identity;
- if a <registration> element with state attribute "terminated", i.e. deregistered, is received for one or more public user identities, the UE shall store the indicated public user identities as deregistered and shall remove any associated GRUUs; and
NOTE 1: There can be public user identities which are automatically registered within the registrar (S-CSCF) of the user upon registration of one public user identity or when S-CSCF receives a Push-Profile-Request (PPR) from the HSS (as described in 3GPP TS 29.228 [14]) changing the status of a public user identity associated with a registered implicit set from barred to non-barred. Usually these automatically or implicitly registered public user identities belong to the same service profile of the user and they might not be available within the UE. The implicitly registered public user identities can also belong to different service profiles. The here-described procedures provide a different mechanism (to the 200 (OK) response to the REGISTER request) to inform the UE about these automatically registered public user identities.
NOTE 2: RFC 5628 [94] provides guidance on the management of temporary GRUUs, utilizing information provided in the reg event notification.
- follow the procedures specified in RFC 6665 [28]. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.2.2 General SUBSCRIBE requirements | If the UE receives a 503 (Service Unavailable) response to an initial SUBSCRIBE request containing a Retry-After header field, then the UE shall not automatically reattempt the request until after the period indicated by the Retry-After header field contents.
5.1.2A Generic procedures applicable to all methods excluding the REGISTER method
5.1.2A.1 UE-originating case
5.1.2A.1.1 General
The procedures of this subclause are general to all requests and responses, except those for the REGISTER method.
When the UE re-uses a previously registered contact address, the UE shall remove any parameters dedicated to registration from the Contact header field (e.g. "expires").
When the UE sends any request, the UE shall use either a given contact address that has been previously registered or a registration flow and the associated contact address (if the multiple registration mechanism is used) and shall:
- if IMS AKA is in use as a security mechanism:
a) if the UE has not obtained a GRUU, populate the Contact header field of the request with the protected server port and the respective contact address; and
b) include the protected server port and the respective contact address in the Via header field entry relating to the UE;
- if SIP digest without TLS is in use as a security mechanism:
a) if the UE has not obtained a GRUU, populate the Contact header field of the request with the port value of an unprotected port and the contact address where the UE expects to receive subsequent mid-dialog requests;
b) populate the Via header field of the request with the port value of an unprotected port and the respective contact address where the UE expects to receive responses to the request; and
c) if a nonce value for proxy authentication is stored for the related registration or registration flow (if the multiple registration mechanism is used), insert a Proxy-Authorization header field containing a challenge response, constructed using the stored nonce value for proxy authentication for the same registration or registration flow (if the multiple registration mechanism is used), "algorithm", "cnonce", "qop", and "nc" header field parameters as specified in RFC 7616 [286] and RFC 8760 [287];
- if SIP digest with TLS is in use as a security mechanism:
a) if the UE has not obtained a GRUU, populate the Contact header field of the request with the protected server port;
b) include the protected server port in the Via header field entry relating to the UE; and
c) if a nonce value for proxy authentication is stored for the related registration or registration flow (if the multiple registration mechanism is used), insert a Proxy-Authorization header field containing a challenge response, constructed using the stored nonce value for proxy authentication for the same registration or registration flow (if the multiple registration mechanism is used), "algorithm", "cnonce", "qop", and "nc" header field parameters as specified in RFC 7616 [286] and RFC 8760 [287];
- if NASS-IMS bundled authentication is in use as a security mechanism, and therefore no port is provided for subsequent SIP messages by the P-CSCF during registration, the UE shall send any request to the same port used for the initial registration as described in subclause 5.1.1.2;
- if GPRS-IMS-Bundled authentication is in use as a security mechanism, and therefore no port is provided for subsequent SIP messages by the P-CSCF during registration, the UE shall send any request to the same port used for the initial registration as described in subclause 5.1.1.2.
If SIP digest without TLS is used, the UE shall not include RFC 3329 [48] header field s in any SIP messages.
When SIP digest is in use, upon receiving a 407 (Proxy Authentication Required) response to an initial request, the originating UE shall:
- extract the digest-challenge parameters as indicated in RFC 7616 [286] and RFC 8760 [287] from the Proxy-Authenticate header field;
- if the contained nonce value is associated to the realm used for the related REGISTER request authentication, store the contained nonce as a nonce value for proxy authentication associated to the same registration or registration flow (if the multiple registration mechanism is used) and shall delete any other previously stored nonce value for proxy authentication for this registration or registration flow;
- calculate the response as described in RFC 7616 [286] and RFC 8760 [287] using the stored nonce value for proxy authentication associated to the same registration or registration flow (if the multiple registration mechanism is used); and
- send a new request containing a Proxy-Authorization header field in which the header field parameters are populated as defined in RFC 7616 [286] and RFC 8760 [287] using the calculated response.
Where a security association or TLS session exists, the UE shall discard any SIP response that is not protected by the security association or TLS session and is received from the P-CSCF outside of the registration and authentication procedures. The requirements on the UE within the registration and authentication procedures are defined in subclause 5.1.1.
For a UE performing the functions of an external attached network operating in static mode, authentication can take place without a registration based on TLS client certificate. Before any originating or terminating procedures can take place between the UE performing the functions of an external attached operating in static mode and the P-CSCF or between the UE performing the functions of an external attached network operating in static mode and the IBCF of the IMS network, for security and authentication between the UE performing the functions of an external attached network operating in static mode and the IMS network, the UE performing the functions of an external attached network operating in static mode shall use the TLS procedures according to 3GPP TS 33.310 [19D] using certificates.
In accordance with RFC 3325 [34] the UE may insert a P-Preferred-Identity header field in any initial request for a dialog or request for a standalone transaction as a hint for creation of an asserted identity (contained in the P-Asserted-Identity header field) within the IM CN subsystem.
NOTE 1: Since the S-CSCF uses the P-Asserted-Identity header field when checking whether the UE originating request matches the initial filter criteria, the P-Preferred-Identity header field inserted by the UE determines which services and applications are invoked.
When sending any initial request for a dialog or request for a standalone transaction using either a given contact address that has been previously registered or a registration flow and the associated contact address (if the multiple registration mechanism is used), the UE may include any of the following in the P-Preferred-Identity header field:
- a public user identity which has been registered by the user with the respective contact address;
- an implicitly registered public user identity returned in a registration-state event package of a NOTIFY request whose <uri> sub-element inside the <contact> sub-element of the <registration> element is the same as the contact address being used for this request and was not subsequently deregistered or that has not expired; or
- any other public user identity which the user has assumed by mechanisms outside the scope of this specification to have a current registration.
NOTE 2: The temporary public user identity specified in subclause 5.1.1.1 is not a public user identity suitable for use in the P-Preferred-Identity header field.
NOTE 3: Procedures in the network require international public telecommunication numbers when telephone numbers are used in P-Preferred-Identity header field.
NOTE 4: A number of header fields can reveal information about the identity of the user. Where privacy is required, implementers should also give consideration to other header fields that can reveal identity information. RFC 3323 [33] subclause 4.1 gives considerations relating to a number of header fields.
Where privacy is required, in any initial request for a dialog or request for a standalone transaction, the UE shall set a display-name of the From header field to "Anonymous" as specified in RFC 3261 [26] and set an addr-spec of the From header field to Anonymous User Identity as specified in 3GPP TS 23.003 [3].
NOTE 5: The contents of the From header field are not necessarily modified by the network based on any privacy specified by the user either within the UE indication of privacy or by network subscription or network policy. Therefore the user should include the value "Anonymous" whenever privacy is explicitly required. As the user can well have privacy requirements, terminal manufacturers should not automatically derive and include values in this header field from the public user identity or other values stored in or derived from the UICC. Where the user has not expressed a preference in the configuration of the terminal implementation, the implementation should assume that privacy is required. Users that require to identify themselves, and are making calls to SIP destinations beyond the IM CN subsystem, where the destination does not implement RFC 3325 [34], will need to include a value in the From header field other than Anonymous.
The UE shall determine the public user identity to be used for this request as follows:
1) if a P-Preferred-Identity was included, then use that as the public user identity for this request; or
2) if no P-Preferred-Identity was included, then use the default public user identity for the security association or TLS session and the associated contact address as the public user identity for this request;
The UE shall not include its "+sip.instance" header field parameter in the Contact header field in its non-register requests and responses except when the request or response is guaranteed to be sent to a trusted intermediary that will remove the "+sip.instance" header field parameter prior to forwarding the request or response to the destination.
NOTE 6: Such trusted intermediaries include an AS that all such requests as part of an application or service traverse. In order to ensure that all requests or responses containing the "+sip.instance" header field parameter are forwarded via the trusted intermediary the UE needs to have first verified that the trusted intermediary is present (e.g. first contacted via a registration or configuration procedure). Including the "+sip.instance" header field parameter containing an IMEI URN does not violate RFC 7254 [153] even when the UE requests privacy using RFC 3323 [33].
If this is a request for a new dialog, the Contact header field is populated as follows:
1) a contact header value which is one of:
- if a public GRUU value ("pub-gruu" header field parameter) has been saved associated with the public user identity to be used for this request, and the UE does not indicate privacy of the P-Asserted-Identity, then the UE should insert the public GRUU ("pub-gruu" header field parameter) value as specified in RFC 5627 [93]; or
- if a temporary GRUU value ("temp-gruu" header field parameter) has been saved associated with the public user identity to be used for this request, and the UE does indicate privacy of the P-Asserted-Identity, then the UE should insert the temporary GRUU ("temp-gruu" header field parameter) value as specified in RFC 5627 [93];
- otherwise, a SIP URI containing the contact address of the UE that has been previously registered without any contact parameters dedicated to registration procedure;
NOTE 7: The above items are mutually exclusive.
2) include an "ob" SIP URI parameter, if the UE supports multiple registrations, and the UE wants all subsequent requests in the dialog to arrive over the same flow identified by the flow token as described in RFC 5626 [92];
3) if the request is related to an IMS communication service that requires the use of an ICSI then the UE shall include in a g.3gpp.icsi-ref media feature tag, as defined in subclause 7.9.2 and RFC 3841 [56B], the ICSI value (coded as specified in subclause 7.2A.8.2) for the IMS communication service. The UE may also include other ICSI values that the UE is prepared to use for all dialogs with the terminating UE(s); and
4) if the request is related to an IMS application that is supported by the UE, then the UE may include in a g.3gpp.iari-ref media feature tag, as defined in subclause 7.9.3 and RFC 3841 [56B], the IARI value (coded as specified in subclause 7.2A.9.2) that is related to the IMS application and that applies for the dialog.
If this is a request within an existing dialog, and the request includes a Contact header field, then the UE should insert the previously used Contact header field.
If the UE support multiple registrations as specified in RFC 5626 [92], the UE should include option-tag "outbound" in the Supported header field.
If this is a request for a new dialog or standalone transaction and the request is related to an IMS communication service that requires the use of an ICSI then the UE:
1) shall include the ICSI value (coded as specified in subclause 7.2A.8.2), for the IMS communication service that is related to the request in a P-Preferred-Service header field according to RFC 6050 [121]. If a list of network supported ICSI values was received as specified in 3GPP TS 24.167 [8G], the UE shall only include an ICSI value that is in the received list;
NOTE 8: The UE only receives those ICSI values corresponding to the IMS communication services that the network provides to the user.
2) may include an Accept-Contact header field containing an ICSI value (coded as specified in subclause 7.2A.8.2) that is related to the request in a g.3gpp.icsi-ref media feature tag as defined in subclause 7.9.2 if the ICSI for the IMS communication service is known. The UE may remove one or more subclasses from an ICSI when including it in an Accept-Contact header field provided that the included ICSI corresponds to an IMS communication service.
NOTE 9: If the UE includes the same ICSI values into the Accept-Contact header field and the P-Preferred-Service header field, there is a possibility that one of the involved S-CSCFs or an AS changes the ICSI value in the P-Asserted-Service header field, which results in the message including two different ICSI values (one in the P-Asserted-Service header field, changed in the network and one in the Accept-Contact header field).
If an IMS application indicates that an IARI is to be included in a request for a new dialog or standalone transaction, the UE shall include an Accept-Contact header field containing an IARI value (coded as specified in subclause 7.2A.9.2) that is related to the request in a g.3gpp.iari-ref media feature tag as defined in subclause 7.9.3 and RFC 3841 [56B].
NOTE 10: RFC 3841 [56B] allows multiple Accept-Contact header fields along with multiple Reject-Contact header fields in a SIP request, and within those header fields, expressions that include one or more logical operations based on combinations of media feature tags. Which registered UE will be contacted depends on the Accept-Contact header field and Reject-Contact header field combinations included that evaluate to a logical expression and the relative qvalues of the registered contacts for the targeted registered public user identity. There is therefore no guarantee that when multiple Accept-Contact header fields or additional Reject-Contact header field(s) along with the Accept-Contact header field containing the ICSI value or IARI value are included in a request that the request will be routed to a contact that registered the same ICSI value or IARI value. Charging and accounting is based upon the contents of the P-Asserted-Service header field and the actual media related contents of the SIP request and not the Accept-Contact header field contents or the contact reached.
NOTE 11: The UE only includes the header field parameters "require" and "explicit" in the Accept-Contact header field containing the ICSI value or IARI value if the IMS communication service absolutely requires that the terminating UE understand the IMS communication service in order to be able to accept the session. Including the header field parameters "require" and "explicit" in Accept-Contact header fields in requests which don't absolutely require that the terminating UE understand the IMS communication service in order to accept the session creates an interoperability problem for sessions which otherwise would interoperate and violates the interoperability requirements for the ICSI in 3GPP TS 23.228 [7].
After the dialog is established the UE may change the dialog capabilities (e.g. add a media or request a supplementary service) if defined for the IMS communication service as identified by the ICSI value using the same dialog. Otherwise, the UE shall initiate a new initial request to the other user.
The UE can indicate privacy of the P-Asserted-Identity that will be generated by the P-CSCF in accordance with RFC 3323 [33], and the additional requirements contained within RFC 3325 [34].
If resource priority in accordance with RFC 4412 [116] is required for a dialog, then the UE shall include the Resource-Priority header field in all requests associated with that dialog.
NOTE 12: The case where the UE is unaware of the requirement for resource priority because the user requested the capability as part of the dialstring falls outside the scope of this requirement. Such cases can exist and will need to be dealt with by an appropriate functional entity (e.g. P-CSCF) to process the dialstring. For certain national implementations, signalling of a Resource-Priority header field to or from a UE is not required.
If available to the UE (as defined in the access technology specific annexes for each access technology), the UE shall insert a P-Access-Network-Info header field into any request for a dialog, any subsequent request (except CANCEL requests) or response (except CANCEL responses) within a dialog or any request for a standalone method (see subclause 7.2A.4). Insertion of the P-Access-Network-Info header field into the ACK request is optional.
NOTE 13: During the dialog, the points of attachment to the IP-CAN of the UE can change (e.g. UE connects to different cells). The UE will populate the P-Access-Network-Info header field in any request or response within a dialog with the current point of attachment to the IP-CAN (e.g. the current cell information).
NOTE 14: The value of the P-Access-Network-Info header field could be stale if the point of attachment of the UE with the network changes before the message is received by the network.
The UE shall build a proper preloaded Route header field value for all new dialogs and standalone transactions. The UE shall build a list of Route header field values made out of the following, in this order:
a) the P-CSCF URI containing the IP address acquired at the time of the P-CSCF discovery procedures which was used in registration of the contact address (or registration flow); and
NOTE 15: If the UE is provisioned with or receives a FQDN at the time of the P-CSCF discovery procedures, the FQDN is resolved to an IP address at the time of the P-CSCF discovery procedures.
b) the P-CSCF port based on the security mechanism in use:
- if IMS AKA or SIP digest with TLS is in use as a security mechanism, the protected server port learnt during the registration procedure;
- if SIP digest without TLS, NASS-IMS bundled authentication or GPRS-IMS-Bundled authentication is in use as a security mechanism, the unprotected server port used during the registration procedure;
c) and the values received in the Service-Route header field saved from the 200 (OK) response to the last registration or reregistration of the public user identity with associated contact address.
NOTE 16: When the UE registers multiple contact addresses, there will be a list of Service-Route headers for each contact address. When sending a request using a given contact address and the associated security associations or TLS session, the UE will use the corresponding list of Service-Route headers to construct a list of Route headers.
The UE may indicate that proxies should not fork the request by including a "no-fork" directive within the Request-Disposition header field in the request as described in RFC 3841 [56B].
If a request is for a new dialog or standalone transaction, and the request matches a trigger for starting logging of SIP signalling, as described in RFC 8497 [140] and configured in the trace management object defined in 3GPP TS 24.323 [8K], the UE shall:
- start to log SIP signalling for this dialog; and
- in any requests or responses sent on this dialog, append a "logme" header field parameter to the SIP Session-ID header field.
If a request or response is sent on a dialog for which logging of signalling is in progress, the UE shall check whether a trigger for stopping logging of SIP signalling has occurred, as described in RFC 8497 [140] and configured in the trace management object defined in 3GPP TS 24.323 [8K].
a) If a stop trigger event has occurred, the UE shall stop logging of signalling; or
b) if a stop trigger event has not occurred, the UE shall:
- in any requests or responses sent on this dialog, append a "logme" header field parameter to the SIP Session-ID header field; and
- log the request.
If the UE receives a 1xx or 200 (OK) response to an initial request for a dialog, the response containing a P-Asserted-Identity header field set to an emergency number as specified in 3GPP TS 22.101 [1A], the UE procedures in subclause 5.1.6.10 apply.
If the UE receives a 3xx response containing a Contact header field:
1) if the 3xx response is a 380 (Alternative Service) response to an INVITE request the response containing a P-Asserted-Identity header field with a value equal to the value of the last entry of the Path header field value received during registration and the response contains a 3GPP IM CN subsystem XML body that includes an <ims-3gpp> element, including a version attribute, with an <alternative-service> child element with the <type> child element set to "emergency" (see table 7.6.2) then the UE shall select a domain in accordance with the conventions and rules specified in 3GPP TS 22.101 [1A] and 3GPP TS 23.167 [4B], and:
- if the CS domain is selected, the UE behavior is defined in subclause 7.1.2 of 3GPP TS 23.167 [4B] and, where appropriate, in the access technology specific annex;
- if the IM CN subsystem is selected, the UE shall apply the procedures in subclause 5.1.6 with the exception of selecting a domain for the emergency call attempt; and
2) if the response is:
- not a 380 (Alternative Service) response; or
- a 380 (Alternative Service) response, and the response:
i. does not contain a 3GPP IM CN subsystem XML body that includes an <ims-3gpp> element, including a version attribute, with an <alternative-service> child element with the <type> child element set to "emergency" (see table 7.6.2); or
ii. does contain a 3GPP IM CN subsystem XML body that includes an <ims-3gpp> element, including a version attribute, with an <alternative-service> child element with the <type> child element set to "emergency" (see table 7.6.2), and the response;
I) does not contain a P-Asserted-Identity header field; or
II) does contain a P-Asserted-Identity header field with a value not equal to the value of the last entry of the Path header field value received during registration;
the UE should not automatically recurse on the Contact header field without first indicating the identity of the user to which a request will be sent and obtaining authorisation of the served user.
NOTE 17: The last entry on the Path header field value received during registration is the value of the SIP URI of the P-CSCF. If there are multiple registration flows associated with the registration, then the UE has received from the P-CSCF during registration multiple sets of Path header field values. The last entry of the Path header field value corresponding to the flow on which the 380 (Alternative Service) response was received is checked.
NOTE 18: A UE can still automatically recurse on 3xx responses as part of a service if the nature of the service enables the UE to identify 3xx responses as having originated from the home network and networks trusted by the home network and the nature of the service ensures that the charging for the requests sent as a result of the 3xx response is correlated with the original request.
NOTE 19: Automatically recursing on untrusted 3xx responses opens up the UE to being redirected to premium rate URIs without the user's consent.
The UE performing the functions of an external attached network operating in static mode shall send all requests using the already established TLS session as described in this subclause.
A UE supporting RFC 4028 [58], when it receives a 422 (Session Interval Too Small) to an INVITE request where the response contains a Min-SE header field, shall retry the request in accordance with RFC 4028 [58] subclause 7.4.
5.1.2A.1.2 Structure of Request-URI
The UE may include a SIP URI complying with RFC 3261 [26], a tel URI complying with RFC 3966 [22], a pres URI complying with RFC 3859 [179], an im URI complying with RFC 3860 [180], a mailto URI complying with RFC 2368 [181] or a "urn:service:test.sos.ecall" service URN with zero or more further sub-services, complying with RFC 8147 [244].
NOTE: This version of the document does not specify how the UE determines the host part of the SIP URI.
The UE may use non-international formats of E.164 numbers or non-E.164 numbers, including geo-local numbers and home-local numbers and other local numbers (e.g. private number), in the Request-URI.
The actual value of the URI depends on whether user equipment performs an analysis of the dial string input by the end user or not, see subclauses 5.1.2A.1.3 and 5.1.2A.1.4.
5.1.2A.1.3 UE without dial string processing capabilities
In this case the UE does not perform any analysis of the dial string. This requires that the dialling plan is designed so it enables the network to differentiate local numbers from other numbers.
The dial string is sent to the network, in the Request-URI of a initial request or a stand alone transaction, using one of the following formats:
1) a tel-URI, syntactically complying with RFC 3966 [22], with the dial string encoded as a local number followed by a "phone-context" tel URI parameter value;
EXAMPLE: tel:00447700900123;phone-context=example.com
2) a SIP URI, syntactically complying with RFC 3261 [26], with the user=phone parameter, embedding a tel-URI with a "phone-context" tel URI parameter value;
EXAMPLE: sip:00447700900123;
[email protected];user=phone
3) a SIP URI, complying with RFC 3261 [26] and RFC 4967 [103], with the user=dialstring parameter and with a "phone-context" tel-URI parameter value in the user part; or
EXAMPLE: sip:00447700900123;
[email protected];user=dialstring
4) a SIP URI syntactically complying with RFC 3261 [26], where the user part contains the dial string and the domain name is specific enough to enable to network to understand that the user part contains a dial string.
EXAMPLE: sip:[email protected]
For cases 1), 2), and 3) the UE shall set the "phone-context" tel URI parameter in accordance with subclause 5.1.2A.1.5.
5.1.2A.1.4 UE with dial string processing capabilities
In this case the UE performs sufficient dial string analysis (or receives an explicit indication from the user) to identify the type of numbering that is used and processes the dial string accordingly before building the Request-URI.
If the UE detects that a local dialling plan is being used, where the UE is able to identify a global telephone number, the UE shall translate the number into E.164 international format after removing all dial string elements used for local numbering detection purposes (e.g. escape codes).
If the UE detects that a local (private or public) dialling plan is being used and the UE is not able to identify a global number, it may decide to send the dial string unchanged to the network as described in subclause 5.1.2A.1.3 or the UE may decide to alter it to comply with the local numbering plan (e.g. remove all dial string elements used for local numbering detection).
In the latter case the local numbering information is sent using one of the following formats:
1) a tel-URI, complying with RFC 3966 [22], with a local number followed by a "phone-context" tel-URI parameter value;
2) a SIP URI, complying with RFC 3261 [26], with the "user" SIP URI parameter set to "phone" and a user part embedding a local number with a phone-context parameter; and
3) if the UE intends to send information related to supplementary services, a SIP URI, complying with RFC 3261 [26] and RFC 4967 [103], with the "user" SIP URI parameter set to "dialstring" and with a "phone-context" tel URI parameter value in the user part.
The UE shall set the "phone-context" tel URI parameter in accordance with subclause 5.1.2A.1.5.
NOTE: The way how the UE process the dial-string and handles special characters (e.g. pause) in order to produce a conformant SIP URI or tel-URI according to RFC 3966 [22] is implementation specific.
As a general rule, recognition of special service numbers shall take priority over other dialling plan issues. If the dial string equates to a pre-configured service URN as specified in RFC 5031 [69]) then the service-urn should be sent.
5.1.2A.1.5 Setting the "phone-context" tel URI parameter
When the UE uses home-local number, the UE shall include in the "phone-context" tel URI parameter the home network domain name in accordance with RFC 3966 [22].
When the UE uses geo-local number, the UE shall:
- if access technology information available to the UE (i.e., the UE can insert P-Access-Network-Info header field into the request), include the access technology information in the "phone-context" tel URI parameter according to RFC 3966 [22] as defined in subclause 7.2A.10; and
- if access technology information is not available to the UE (i.e., the UE cannot insert P-Access-Network-Info header field into the request), include in the "phone-context" tel URI parameter the home network domain name prefixed by the "geo-local." string according to RFC 3966 [22] as defined in subclause 7.2A.10.
When the UE uses other local numbers, than geo-local number or home local numbers, e.g. private numbers that are different from home-local number or the UE is unable to determine the type of the dialled number, the UE shall include a "phone-context" tel URI parameter set according to RFC 3966 [22], e.g. if private numbers are used a domain name to which the private addressing plan is associated. The "phone-context" value used in the case of other local numbers shall be different from "phone-context" values used with geo-local numbers and home-local numbers.
NOTE 1: The "phone-context" tel URI parameter value can be entered or selected by the subscriber, or can be a "pre-configured" value (e.g. using OMA-DM with the management object specified in 3GPP TS 24.167 [8G]) inserted by the UE.
NOTE 2: The way how the UE determines whether numbers in a non-international format are geo-local, home-local or relating to another network in absence of matching UE configuration in subclause 5.1.2A.1.5A, is implementation specific.
NOTE 3: Home operator's local policy can define a prefix string(s) to enable subscribers to differentiate dialling a geo-local number and/or a home-local number.
5.1.2A.1.5A Policy on local numbers
Policy on local numbers consists of zero or more parts of policy on local numbers
A part of policy on local numbers indicates an IMS communication service (identified by an ICSI) in which the UE is to use a number in non-international format without associated "phone-context" value as:
1) a geo-local number; or
2) a home-local number.
The UE may support the policy on local numbers.
If the UE supports the policy on local numbers:
1) if:
a) the upper layers provide a number in non-international format to be included in Request-URI of a SIP request;
b) the upper layers do not provide a "phone-context" value associated with the number;
c) the UE is not configured to associate a particular "phone-context" value with the number; and
d) the SIP request is related to an IMS communication service (identified by an ICSI) indicated in a part of the policy on local numbers such that:
i) the part of the policy on local numbers indicates to use the number as a geo-local number, then the UE shall use the number as a geo-local number in subclause 5.1.2A.1.5; and
ii) the part of the policy on local numbers indicates to use the number as a home-local number, then the UE shall use the number as a home-local number in subclause 5.1.2A.1.5; and
2) the UE may support being configured with the policy on local numbers using one or more of the following methods:
a) the Policy_on_local_numbers node of the EFIMSConfigData file described in 3GPP TS 31.102 [15C];
b) the Policy_on_local_numbers node of the EFIMSConfigData file described in 3GPP TS 31.103 [15B]; and
c) the Policy_on_local_numbers node of 3GPP TS 24.167 [8G].
If the UE is configured with both the Policy_on_local_numbers node of 3GPP TS 24.167 [8G] and the Policy_on_local_numbers node of the EFIMSConfigData file described in 3GPP TS 31.102 [15C] or the Policy_on_local_numbers node of the EFIMSConfigData file described in 3GPP TS 31.103 [15B], then the Policy_on_local_numbers node of the EFIMSConfigData file shall take precedence.
NOTE: Precedence for files configured on both the USIM and ISIM is defined in 3GPP TS 31.103 [15B].
5.1.2A.1.6 Abnormal cases
In the event the UE receives a 504 (Server Time-out) response containing:
1) a P-Asserted-Identity header field set to a value equal to a URI:
a) from the Service-Route header field value received during registration; or
b) from the Path header field value received during registration; and
NOTE 1: If there are multiple registration flows associated with the registration, then the UE has received from the P-CSCF during registration multiple sets of Path header field and Service-Route header field values. The Path header field value and Service-Route header field value corresponding to the flow on which the 504 (Server Time-out) response was received are checked.
2) a Content-Type header field set according to subclause 7.6 (i.e. "application/3gpp-ims+xml"), independent of the value or presence of the Content-Disposition header field, independent of the value or presence of Content-Disposition parameters,
then the following treatment is applied:
a) if the 504 (Server Time-out) response includes an IM CN subsystem XML body as described in subclause 7.6 with the <ims-3gpp> element, including a version attribute, with the <alternative-service> child element:
A) with the <type> child element set to "restoration" (see table 7.6.2); and
B) with the <action> child element set to "initial-registration" (see table 7.6.3);
then the UE:
- shall initiate S-CSCF restoration procedures by performing an initial registration as specified in subclause 5.1.1.2; and
- may provide an indication to the user based on the text string contained in the <reason> child element of the <alternative-service> child element of the <ims-3gpp> element.
NOTE 2: If the UE has discovered multiple P-CSCF addresses and has information that the P-CSCF was unable to forward the request resulting in sending back the 504 (Server Time-out) response, when starting the initial registration it is appropriate for the UE to select a P-CSCF address different from the one used for the registration binding on which the 504 (Server Time-out) response was received.
When sending a request from a contact address that has been previously registered (or via a registration flow if the multiple registration mechanism is used) which is bound to a public user identity by registration which used a P-CSCF address, and:
- if timer F expires in the "Trying" state of non-INVITE client transaction as described in IETF RFC 3261 [26];
- if a fatal transport error is reported by the transport layer in the "Trying" state of non-INVITE client transaction as described in IETF RFC 3261 [26];
- if timer B expires in the "Calling" state of INVITE client transaction as described in IETF RFC 6026 [163]; or
- if a fatal transport error is reported by the transport layer in "Calling" state of INVITE client transaction as described in IETF RFC 6026 [163];
then the UE shall:
1) if the multiple registration mechanism is not used:
A) consider the contact address as not bound to any public user identity;
B) mark the currently used P-CSCF address (i.e. P-CSCF address using which the contact address was registered) as unavailable;
C) if there is a locally stored P-CSCF addressas specified in subclause 5.1.9 which is different than thecurrently used P-CSCF address and which is not marked as unavailable, initiate an initial registration as specified in subclause 5.1.1.2 using that P-CSCF; and
D) if there is no locally stored P-CSCF address as specified in subclause 5.1.9 which is different than the currently used P-CSCF address and which is not marked as unavailable, get a new set of P-CSCF addresses as described in subclause 9.2.1 unless otherwise specified in the access specific annexes (as described in annex B, annex L or annex U) and initiate an initial registration as specified in subclause 5.1.1.2; and
2) if the multiple registration mechanism is used, declare the registration flow dead as defined in RFC 5626 [92] and mark the currently used P-CSCF address as unavailable.
NOTE 3: When a fatal transport error occurs, further steps might be necessary to restore the transport layer, possibly including re-establishment of an IP-CAN bearer.
When sending a request from a contact address that has been previously registered (or via a registration flow if the multiple registration mechanism is used) which is bound to a public user identity by registration which used a P-CSCF address, and if a 503 (Service Unavailable) response without a Retry-After header field is received for request as described in IETF RFC 3261 [26], the UE shall:
1) if the multiple registration mechanism is not used:
A) consider the contact address as not bound to any public user identity;
B) mark the currently used P-CSCF address (i.e. P-CSCF address using which the contact address was registered) as unavailable;
C) if there is a locally stored P-CSCF address as specified in subclause 5.1.9 which is different than the currently used P-CSCF address and which is not marked as unavailable, initiate an initial registration as specified in subclause 5.1.1.2 using that P-CSCF; and
D) if there is no locally stored P-CSCF address as specified in subclause 5.1.9 which is different than the currently used P-CSCF address and which is not marked as unavailable, get a new set of P-CSCF addresses as described in subclause 9.2.1 unless otherwise specified in the access specific annexes (as described in annex B, annex L or annex U) and initiate an initial registration as specified in subclause 5.1.1.2; and
2) if the multiple registration mechanism is used, declare the registration flow dead as defined in RFC 5626 [92] and mark the currently used P-CSCF address as unavailable.
When sending a request from a contact address that has been previously registered (or via a registration flow if the multiple registration mechanism is used) which is bound to a public user identity by registration which used a P-CSCF address, and if a 503 (Service Unavailable) response with a Retry-After header field is received for request as described in IETF RFC 3261 [26] and :
- if the request was a non-INVITE request, the Retry-After header field indicates a time bigger than value for timer F as specified in table 7.7.1; and
- if the request was an INVITE request, the Retry-After header field indicates a time bigger than value for timer B as specified in table 7.7.1;
the UE shall:
1) if the multiple registration mechanism is not used:
A) consider the contact address as not bound to any public user identity;
B) mark the currently used P-CSCF address (i.e. P-CSCF address using which the contact address was registered) as unavailable for the time indicated by the Retry-After header field;
C) if there is a locally stored P-CSCF address as specified in subclause 5.1.9 which is different than the currently used P-CSCF address and which is not marked as unavailable, initiate an initial registration as specified in subclause 5.1.1.2 using that P-CSCF; and
D) if there is no locally stored P-CSCF address as specified in subclause 5.1.9 which is different than the currently used P-CSCF address and which is not marked as unavailable, get a new set of P-CSCF addresses as described in subclause 9.2.1 unless otherwise specified in the access specific annexes (as described in annex B, annex L or annex U) and initiate an initial registration as specified in subclause 5.1.1.2; and
2) if the multiple registration mechanism is used, declare the registration flow dead as defined in RFC 5626 [92] and mark the currently used P-CSCF address as unavailable for the time indicated by the Retry-After header field.
NOTE 4: if the Retry-After header field indicates time smaller than the value for timer F or timer B as specified in table 7.7.1, the UE continues using the currently used P-CSCF address.
5.1.2A.2 UE-terminating case
The procedures of this subclause are general to all requests and responses, except those for the REGISTER method.
Where a security association or TLS session exists, the UE shall discard any SIP request that is not protected by the security association or TLS session and is received from the P-CSCF outside of the registration and authentication procedures. The requirements on the UE within the registration and authentication procedures are defined in subclause 5.1.1.
If an initial request contains an Accept-Contact header field containing the g.3gpp.icsi-ref media feature tag with an ICSI value, the UE should invoke the IMS application that is the best match for the ICSI value.
If an initial request contains an Accept-Contact header field containing the g.3gpp.iari-ref media feature tag with an IARI value the UE should invoke the IMS application that is the best match for the IARI value.
The UE can receive multiple ICSI values, IARI values or both in an Accept-Contact header field. In this case it is up to the implementation which of the multiple ICSI values or IARI values the UE takes action on.
NOTE 1: The application verifies that the contents of the request (e.g. SDP media capabilities, Content-Type header field) are consistent with the ICSI value in the g.3gpp.icsi-ref media feature tag and IARI value contained in the g.3gpp.iari-ref media feature tag.
If an initial request does not contain an Accept-Contact header field containing a g.3gpp.icsi-ref media feature tag or a g.3gpp.iari-ref media feature tag the UE shall invoke the application that is the best match based on the contents of the request (e.g. SDP media capabilities, Content-Type header field, media feature tag).
The UE can indicate privacy of the P-Asserted-Identity that will be generated by the P-CSCF in accordance with RFC 3323 [33], and the additional requirements contained within RFC 3325 [34].
NOTE 2: In the UE-terminating case, this version of the document makes no provision for the UE to provide a P-Preferred-Identity in the form of a hint.
NOTE 3: A number of header fields can reveal information about the identity of the user. Where, privacy is required, implementers should also give consideration to other header fields that can reveal identity information. RFC 3323 [33] subclause 4.1 gives considerations relating to a number of header fields.
The UE shall not include its "+sip.instance" header field parameter in the Contact header field in its non-register requests and responses except when the request or response is guaranteed to be sent to a trusted intermediary that will remove the "+sip.instance" header field parameter prior to forwarding the request or response to the destination.
NOTE 4: Such trusted intermediaries include an AS that all such requests as part of an application or service traverse. In order to ensure that all requests or responses containing the "+sip.instance" header field parameter are forwarded via the trusted intermediary the UE needs to have first verified that the trusted intermediary is present (e.g first contacted via a registration or configuration procedure). Including the "+sip.instance" header field parameter containing an IMEI URN does not violate RFC 7254 [153] even when the UE requests privacy using RFC 3323 [33].
If the response includes a Contact header field, and the response is sent within an existing dialog, and the Contact address previously used in the dialog was a GRUU, then the UE should insert the previously used GRUU value in the Contact header field as specified in RFC 5627 [93].
If the response includes a Contact header field, and the response is not sent within an existing dialog, the Contact header field is populated as follows:
1) if a public GRUU value ("pub-gruu" header field parameter) has been saved associated with the public user identity from the P-Called-Party-ID header field, and the UE does not indicate privacy of the contents of the P-Asserted-Identity header field, then the UE should insert the public GRUU ("pub-gruu" header field parameter) value as specified in RFC 5627 [93];
2) if a temporary GRUU value ("temp-gruu" header field parameter) has been saved associated with the public user identity from the P-Called-Party-ID header field, and the UE does indicate privacy of the P-Asserted-Identity, then should insert the temporary GRUU ("temp-gruu" header field parameter) value in the Contact header field as specified in RFC 5627 [93];
NOTE 5: The above items 1 and 2 are mutually exclusive.
3) if the request is related to an IMS communication service that requires the use of an ICSI then the UE shall include in a g.3gpp.icsi-ref media feature tag as defined in subclause 7.9.2 and RFC 3841 [56B] the ICSI value (coded as specified in subclause 7.2A.8.2), for the IMS communication service and then the UE may include the IARI value for any IMS application that applies for the dialog, (coded as specified in subclause 7.2A.9.2), that is related to the request in a g.3gpp.iari-ref media feature tag as defined in subclause 7.9.3 and RFC 3841 [56B]. The UE may also include other ICSI values that the UE is prepared to use for all dialogs with the originating UE(s) and other IARI values for the IMS application that is related to the IMS communication service; and
4) if the request is related to an IMS application that is supported by the UE when the use of an ICSI is not needed, then the UE may include the IARI value (coded as specified in subclause 7.2A.9.2), that is related to any IMS application and that applies for the dialog, in a g.3gpp.iari-ref media feature tag as defined in subclause 7.9.3 and RFC 3841 [56B].
After the dialog is established the UE may change the dialog capabilities (e.g. add a media or request a supplementary service) if defined for the IMS communication service as identified by the ICSI value using the same dialog. Otherwise, the UE shall initiate a new initial request to the other user.
If the UE did not insert a GRUU in the Contact header field then the UE shall include a contact address that has been previously registered with contact parameters used for registration removed and a port in the address in the Contact header field as follows:
- if IMS AKA or SIP digest with TLS is being used as a security mechanism, the protected server port value as in the initial registration; or
- if SIP digest without TLS is being used as a security mechanism, the port value of an unprotected port where the UE expects to receive subsequent mid-dialog requests. The UE shall set the unprotected port value to the port value used in the initial registration.
If the UE receives a Resource-Priority header field in accordance with RFC 4412 [16] in an initial request for a dialog, then the UE shall include the Resource-Priority header field in all requests associated with that dialog.
NOTE 6: For certain national implementations, signalling of a Resource-Priority header field to and from a UE is not required.
If available to the UE (as defined in the access technology specific annexes for each access technology), the UE shall insert a P-Access-Network-Info header field into any response to a request for a dialog, any subsequent request (except CANCEL requests) or response (except CANCEL responses) within a dialog or any response to a standalone method (see subclause 7.2A.4).
The terminating UE shall not include the P-Early-Media header field in any SIP messages, unless the terminating UE is a UE performing the functions of an external attached network that is allowed to send early media.
If a request or response is sent on a dialog for which logging of signalling is in progress, the UE shall check whether a trigger for stopping logging of SIP signalling has occurred, as described in RFC 8497 [140] and configured in the trace management object defined in 3GPP TS 24.323 [8K].
a) If a stop trigger event has occurred, the UE shall stop logging of signalling; or
b) if a stop trigger event has not occurred, the UE shall:
- in any requests or responses sent on this dialog, append a "logme" header field parameter to the SIP Session-ID header field; and
- log the request or response.
If the UE does not support a transfer of an updated MSD for PSAP callback specified in clause 5.1.6B, the UE shall not support RFC 7090 [209] and, in this version of the specification, the UE shall not perform any specific procedures beyond those defined in RFC 3261 [26] for the Priority header field.
NOTE 7: The mechanism specified in RFC 7090 [209] is based on the presence of a trust domain for the Priority header field in the operator's network. The UE is not aware whether a trust domain for the Priority header field exists in the operator's network.
If the terminating UE needs to retrieve the last service access number when the AS applies a number translation as described in subclause 5.7.1.22; the terminating UE can find the requested service access number in the hi-entry within the History-Info header field having a hi-index that match the "mp" or "rc" header field parameter value of the last hi-entry containing a "cause" SIP URI parameter, defined in RFC 4458 [68], set to the value "380" defined in RFC 8119 [230]. If no "mp" or "rc" header field parameter is received in the concerned hi-entry, the service access number can be found in the hi-entry preceding the hi-entry with the "cause" SIP URI parameter set to "380".
If the terminating UE
a) supports calling number verification status determination;
b) during registration determined that the home network supports calling number verification using signature verification as and attestation information, as defined in subclause 3.1; and
c) receives initial INVITE request for a dialog or a MESSAGE request containing a P-Asserted-Identity header field or a From header field with a "verstat" tel URI parameter in a tel URI or a SIP URI with a user=phone parameter;
then the terminating UE shall:
a) determine the calling number verification status based on the "verstat" tel URI parameter value; and
b) if unable to determine the calling number verification status based on the "verstat" parameter value, discard the parameter and treat the P-Asserted-Identity header field and the From header field in the same way as if the parameter would not have been included. |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.3 Call initiation - UE-originating case | |
d3a3ac3f64ab68e4fcef5ea9a665f70a | 24.229 | 5.1.3.1 Initial INVITE request | Where multiple domains exist for initiating a call/session, before sending an initial INVITE request, the UE shall perform access domain selection in accordance with the appropriate specification for the IP-CAN in use, taking into account the media to be requested. Access domain selection allows the policy of the network operator to be taken into account before the initial INVITE request is sent. Access dependent aspects of access domain selection are defined in the access technology specific annexes for each access technology.
Upon generating an initial INVITE request, the UE shall include the Accept header field with "application/sdp", the MIME type associated with the 3GPP IM CN subsystem XML body (see subclause 7.6.1) and any other MIME type the UE is willing and capable to accept.
The "integration of resource management and SIP" extension is hereafter in this subclause referred to as "the precondition mechanism" and is defined in RFC 3312 [30] as updated by RFC 4032 [64].
The preconditions mechanism should be supported by the originating UE.
If the precondition mechanism is disabled as specified in subclause 5.1.5A, the UE shall not use the precondition mechanism.
The UE may initiate a session without the precondition mechanism if the originating UE does not require local resource reservation.
NOTE 1: The originating UE can decide if local resource reservation is required based on e.g. application requirements, current access network capabilities, local configuration, etc.
In order to allow the peer entity to reserve its required resources, if the precondition mechanism is enabled as specified in subclause 5.1.5A; the originating UE supporting the precondition mechanism should make use of the precondition mechanism, even if it does not require local resource reservation.
Upon generating an initial INVITE request using the precondition mechanism, the UE shall:
- indicate the support for reliable provisional responses and specify it using the Supported header field; and
- indicate the support for the preconditions mechanism and specify it using the Supported header field.
Upon generating an initial INVITE request using the precondition mechanism, the UE shall not indicate the requirement for the precondition mechanism by using the Require header field.
During the session initiation, if the originating UE indicated the support for the precondition mechanism in the initial INVITE request and:
a) the received response with an SDP body includes a Require header field with "precondition" option-tag, the originating UE shall include a Require header field with the "precondition" option-tag:
- in subsequent requests that include an SDP body, that the originating UE sends in the same dialog as the response is received from; and
- in responses with an SDP body to subsequent requests that include an SDP body and include "precondition" option-tag in Supported header field or Require header field received in-dialog; or
b) the received response with an SDP body does not include the "precondition" option-tag in the Require header field,
- in subsequent requests that include an SDP body, the originating UE shall not include a Require or Supported header field with "precondition" option-tag in the same dialog;
- in responses with an SDP body to subsequent requests with an SDP body but without "precondition" option-tag in the Require or Supported header field, the originating UE shall not include a Require or Supported header field with "precondition" option-tag in the same dialog; and
- in responses with an SDP body to subsequent requests with an SDP body and with "precondition" option-tag in the Require or Supported header field, the originating UE shall include a Require header field with "precondition" option-tag in the same dialog.
NOTE 2: Table A.4 specifies that UE support of forking is required in accordance with RFC 3261 [26]. The UE can accept or reject any of the forked responses, for example, if the UE is capable of supporting a limited number of simultaneous transactions or early dialogs.
If the precondition mechanism is used, the UE shall, upon successful reservation of local resources, confirm the successful resource reservation (see subclause 6.1.2) within the next SIP request.
NOTE 3: The next SIP request will be either a PRACK request or an UPDATE request.
NOTE 4: The UE can receive a P-Early-Media header field authorizing an early-media flow while the required preconditions, if any, are not met and/or the flow direction is not enabled by the SDP direction parameter. According to RFC 5009 [109], an authorized early-media flow can be established only if the necessary conditions related to the SDP negotiation are met. These conditions can evolve during the session establishment.
NOTE 5: When the UE is confirming the successful resource reservation using an UPDATE request (or a PRACK request) and the UE receives a 180 (Ringing) response or a 200 (OK) response to the initial INVITE request before receiving a 200 (OK) response to the UPDATE request (or a 200 (OK) response to the PRACK request), the UE does not treat this as an error case and does not release the session.
NOTE 6: The UE procedures for rendering of the received early media and of the locally generated communication progress information are specified in 3GPP TS 24.628 [8ZF].
If the UE wishes to receive early media authorization indications, as described in RFC 5009 [109], the UE shall add the P-Early-Media header field with the "supported" parameter to the initial INVITE request.
A UE supporting the Session Timer extension as described in RFC 4028 [58] may support the extension being configured using Session_Timer_Support node specified in 3GPP TS 24.167 [8G].
If the UE supports the Session Timer extension, the UE shall include the option-tag "timer" in the Supported header field and should either insert a Session-Expires header field with the header field value set to the configured session timer interval value, or should not include the Session-Expires header field in the initial INVITE request. The header field value of the Session-Expires header field may be configured using local configuration or using the Session_Timer_Initial_Interval node specified in 3GPP 24.167 [8G]. If the UE is configured with both the local configuration and the Session_Timer_Initial_Interval node specified in 3GPP 24.167 [8G], then the local configuration shall take precedence.
If the UE inserts the Session-Expires header field in the initial INVITE request, the UE may also include the "refresher" parameter with the "refresher" parameter value set to "uac".
When a final answer is received for one of the early dialogs, the UE proceeds to set up the SIP session. The UE shall not progress any remaining early dialogs to established dialogs. Therefore, upon the reception of a subsequent final 200 (OK) response for an INVITE request (e.g., due to forking), the UE shall:
1) acknowledge the response with an ACK request; and
2) send a BYE request to this dialog in order to terminate it.
Upon receiving a 488 (Not Acceptable Here) response to an initial INVITE request, the originating UE should send a new INVITE request containing SDP according to the procedures defined in subclause 6.1.
NOTE 7: An example of where a new request would not be sent is where knowledge exists within the UE, or interaction occurs with the user, such that it is known that the resulting SDP would describe a session that did not meet the user requirements.
Upon receiving a 421 (Extension Required) response to an initial INVITE request in which the precondition mechanism was not used, including the "precondition" option-tag in the Require header field, if the UE supports the precondition mechanism and the precondition mechanism is enabled as specified in subclause 5.1.5A, the originating UE shall:
- send a new INVITE request using the precondition mechanism; and
- send an UPDATE request as soon as the necessary resources are available and a 200 (OK) response for the first PRACK request has been received.
Upon receiving a 503 (Service Unavailable) response to an initial INVITE request containing a Retry-After header field, then the originating UE shall not automatically reattempt the request via the same P-CSCF until after the period indicated by the Retry-After header field contents.
The UE may include a "cic" tel URI parameter in a tel URI, or in the userinfo part of a SIP URI with user=phone, in the Request-URI of an initial INVITE request if the UE wants to identify a user-dialed carrier, as described in RFC 4694 [112].
NOTE 8: The method whereby the UE determines when to include a "cic" tel-URI parameter and what value it should contain is outside the scope of this document (e.g. the UE could use a locally configured digit map to look for special prefix digits that indicate the user has dialled a carrier).
NOTE 9: The value of the "cic" tel-URI parameter reported by the UE is not dependent on UE location (e.g. the reported value is not affected by roaming scenarios).
In the event the UE receives a 380 (Alternative Service) response to an initial INVITE request the response containing a P-Asserted-Identity header field with a value equal to the value of the last entry of the Path header field value received during registration and the response containing a 3GPP IM CN subsystem XML body that includes an <ims-3gpp> element, including a version attribute, with an <alternative-service> child element with the <type> child element set to "emergency" (see table 7.6.2), the UE shall select a domain in accordance with the conventions and rules specified in 3GPP TS 22.101 [1A] and 3GPP TS 23.167 [4B], and:
- if the CS domain is selected, the UE behavior is defined in subclause 7.1.2 of 3GPP TS 23.167 [4B] and, where appropriate, in the access technology specific annex; and
- if the IM CN subsystem is selected, the UE shall apply the procedures in subclause 5.1.6 with the exception of selecting a domain for the emergency call attempt.
NOTE 10: The last entry on the Path header field value received during registration is the value of the SIP URI of the P-CSCF. If there are multiple registration flows associated with the registration, then the UE has received from the P-CSCF during registration multiple sets of Path header field values. The last entry of the Path header field value corresponding to the flow on which the 380 (Alternative Service) response was received is checked.
Upon receiving a 199 (Early Dialog Terminated) provisional response to an established early dialog the UE shall release resources specifically related to that early dialog.
The UE shall include the media feature tags defined in RFC 3840 [62] and RFC 5688 [120] for all supported streaming media types in the initial INVITE request.
If the UE sends a CANCEL request to cancel an initial INVITE request, the UE shall when applicable include in the CANCEL request a Reason header field with a protocol value set to "RELEASE_CAUSE" and a "cause" header field parameter as specified in subclause 7.2A.18.11.2. The UE may also include the "text" header field parameter with reason-text as specified in subclause 7.2A.18.11.2.
Upon receiving a 500 (Server Internal Error) response to an initial INVITE request including a Reason header field with a protocol value set to "FAILURE_CAUSE" and a cause header field parameter value set to "1" as specified in subclause 7.2A.18.12.2 and a Response-Source header field with a "fe" header field parameter set to "<urn:3gpp:fe:p-cscf.orig>", the UE can determine that the QoS or bearer resources in the originating IP-CAN is not available. |
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