ETSI TS 124 229 V19.6.0 (2026-03)

Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); LTE; 5G; IP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3 (3GPP TS 24.229 version 19.6.0 Release 19)

RTS/TSGC-0124229vj60

General Information

• Status: Not Published
• Technical Committee: 3GPP CT 1 - MM/CC/SM [lu] (formely CN1)
• Current Stage: 8 - Draft receipt by ETSI Secretariat
• Completion Date: 10-Mar-2026

Standards Content (Sample)

TECHNICAL SPECIFICATION
Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS);
LTE;
5G;
IP multimedia call control protocol based on
Session Initiation Protocol (SIP)
and Session Description Protocol (SDP);
Stage 3
(3GPP TS 24.229 version 19.6.0 Release 19)

3GPP TS 24.229 version 19.6.0 Release 19 1 ETSI TS 124 229 V19.6.0 (2026-03)

Reference
RTS/TSGC-0124229vj60
Keywords
5G,GSM,LTE,UMTS
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ETSI
3GPP TS 24.229 version 19.6.0 Release 19 2 ETSI TS 124 229 V19.6.0 (2026-03)
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Legal Notice
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ETSI
3GPP TS 24.229 version 19.6.0 Release 19 3 ETSI TS 124 229 V19.6.0 (2026-03)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 40
1 Scope . 42
2 References . 43
3 Definitions of terms, symbols and abbreviations . 59
3.1 Terms . 59
3.2 Symbols . 67
3.3 Abbreviations . 67
3A Interoperability with different IP-CAN . 70
4 General . 71
4.1 Conformance of IM CN subsystem entities to SIP, SDP and other protocols . 71
4.2 URI and address assignments . 74
4.2A Transport mechanisms . 76
4.2B Security mechanisms . 77
4.2B.1 Signalling security . 77
4.2B.2 Media security . 79
4.3 Routeing principles of IM CN subsystem entities . 82
4.4 Trust domain . 83
4.4.1 General . 83
4.4.2 P-Asserted-Identity . 83
4.4.3 P-Access-Network-Info . 84
4.4.4 History-Info . 84
4.4.5 P-Asserted-Service. 84
4.4.6 Resource-Priority . 84
4.4.7 Reason (in a response) . 84
4.4.8 P-Profile-Key . 84
4.4.9 P-Served-User . 84
4.4.10 P-Private-Network-Indication . 85
4.4.11 P-Early-Media . 85
4.4.12 CPC and OLI . 85
4.4.13 Feature-Caps . 85
4.4.14 Priority . 85
4.4.15 iotl . 85
4.4.16 Restoration-Info . 85
4.4.17 Relayed-Charge . 86
4.4.18 Service-Interact-Info . 86
4.4.19 Cellular-Network-Info . 86
4.4.20 Response-Source . 86
4.4.21 Attestation-Info header field . 86
4.4.22 Origination-Id header field . 86
4.4.23 Additional-Identity header field . 86
4.4.24 Priority-Verstat header field . 86
4.4.25 DC-Info header field . 86
4.5 Charging correlation principles for IM CN subsystems . 87
4.5.1 Overview . 87
4.5.2 IM CN subsystem charging identifier (ICID) . 87
4.5.2A Related ICID . 88
4.5.3 Access network charging information . 88
4.5.3.1 General . 88
4.5.3.2 Access network charging information . 88
4.5.4 Inter operator identifier (IOI) . 89
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4.5.4A Transit inter operator identifier (Transit IOI) . 90
4.5.5 Charging function addresses . 91
4.5.6 Relayed charge parameters . 91
4.5.7 Loopback-indication parameter . 91
4.5.8 IM CN subsystem Functional Entity Identifier . 92
4.5.8.1 General . 92
4.5.8.2 Tracking of IM CN subsystem functional entities generating charging information . 92
4.5.8.3 Tracking of applications generating charging information . 92
4.6 Support of local service numbers . 92
4.7 Emergency service . 92
4.7.1 Introduction. 92
4.7.2 Emergency calls generated by a UE . 92
4.7.3 Emergency calls generated by an AS . 93
4.7.4 Emergency calls received from an enterprise network . 93
4.7.5 Location in emergency calls . 93
4.7.6 eCall type of emergency service . 94
4.8 Tracing of signalling . 95
4.8.1 General . 95
4.8.2 Trace depth . 95
4.9 Overlap signalling . 95
4.9.1 General . 95
4.9.2 Overlap signalling methods . 96
4.9.2.1 In-dialog method . 96
4.9.2.1.1 General . 96
4.9.2.2 Multiple-INVITE method . 96
4.9.2.2.1 General . 96
4.9.3 Routeing impacts . 96
4.9.3.1 General . 96
4.9.3.2 Deterministic routeing . 96
4.9.3.3 Digit collection . 96
4.10 Dialog correlation for IM CN subsystems . 97
4.10.1 General . 97
4.10.2 CONF usage. 97
4.11 Priority mechanisms . 97
4.12 Overload control . 99
4.13 II-NNI traversal scenario . 100
4.13.1 General . 100
4.13.2 Identifying the II-NNI traversal scenario . 100
4.13.3 Security aspects . 100
4.14 Restoration procedures . 101
4.14.1 General . 101
4.14.2 P-CSCF restoration procedures . 101
4.14.3 S-CSCF restoration procedures . 101
4.15 Resource sharing . 102
4.16 Priority sharing . 102
4.17 3GPP PS data off . 102
4.18 Dynamic Service Interaction . 103
4.19 Restricted Local Operator Services . 103
4.20 IMS data channel . 103
5 Application usage of SIP . 104
5.1 Procedures at the UE . 104
5.1.0 General . 104
5.1.1 Registration and authentication. 104
5.1.1.1 General . 104
5.1.1.1A Parameters contained in the ISIM . 104
5.1.1.1B Parameters provisioned to a UE without ISIM or USIM . 105
5.1.1.1B.1 Parameters provisioned in the IMC . 105
5.1.1.1B.2 Parameters when UE does not contain ISIM, USIM or IMC . 105
5.1.1.2 Initial registration . 105
5.1.1.2.1 General . 105
5.1.1.2.2 Initial registration using IMS AKA . 111
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5.1.1.2.3 Initial registration using SIP digest without TLS . 112
5.1.1.2.4 Initial registration using SIP digest with TLS . 112
5.1.1.2.5 Initial registration using NASS-IMS bundled authentication . 113
5.1.1.2.6 Initial registration using GPRS-IMS-Bundled authentication . 113
5.1.1.3 Subscription to the registration-state event package . 114
5.1.1.3A Void. 115
5.1.1.4 User-initiated reregistration and registration of an additional public user identity . 115
5.1.1.4.1 General . 115
5.1.1.4.2 IMS AKA as a security mechanism. 119
5.1.1.4.3 SIP digest without TLS as a security mechanism . 120
5.1.1.4.4 SIP digest with TLS as a security mechanism . 120
5.1.1.4.5 NASS-IMS bundled authentication as a security mechanism . 121
5.1.1.4.6 GPRS-IMS-Bundled authentication as a security mechanism . 121
5.1.1.5 Authentication . 122
5.1.1.5.1 IMS AKA - general . 122
5.1.1.5.2 Void . 123
5.1.1.5.3 IMS AKA abnormal cases . 123
5.1.1.5.4 SIP digest without TLS – general . 124
5.1.1.5.5 SIP digest without TLS – abnormal procedures . 124
5.1.1.5.6 SIP digest with TLS – general . 124
5.1.1.5.7 SIP digest with TLS – abnormal procedures . 125
5.1.1.5.8 NASS-IMS bundled authentication – general . 125
5.1.1.5.9 NASS-IMS bundled authentication – abnormal procedures . 125
5.1.1.5.10 GPRS-IMS-Bundled authentication – general . 125
5.1.1.5.11 GPRS-IMS-Bundled authentication – abnormal procedures . 125
5.1.1.5.12 Abnormal procedures for all security mechanisms . 126
5.1.1.5A Network-initiated re-authentication . 126
5.1.1.5B Change of IPv6 address due to privacy . 126
5.1.1.6 User-initiated deregistration . 127
5.1.1.6.1 General . 127
5.1.1.6.2 IMS AKA as a security mechanism. 129
5.1.1.6.3 SIP digest without TLS as a security mechanism . 130
5.1.1.6.4 SIP digest with TLS as a security mechanism . 130
5.1.1.6.5 NASS-IMS bundled authentication as a security mechanism . 130
5.1.1.6.6 GPRS-IMS-Bundled authentication as a security mechanism . 130
5.1.1.7 Network-initiated deregistration . 131
5.1.2 Subscription and notification . 132
5.1.2.1 Notification about multiple registered public user identities . 132
5.1.2.2 General SUBSCRIBE requirements . 132
5.1.2A Generic procedures applicable to all methods excluding the REGISTER method . 133
5.1.2A.1 UE-originating case . 133
5.1.2A.1.1 General . 133
5.1.2A.1.2 Structure of Request-URI . 138
5.1.2A.1.3 UE without dial string processing capabilities . 139
5.1.2A.1.4 UE with dial string processing capabilities. 139
5.1.2A.1.5 Setting the "phone-context" tel URI parameter . 140
5.1.2A.1.5A Policy on local numbers . 140
5.1.2A.1.6 Abnormal cases . 141
5.1.2A.2 UE-terminating case . 143
5.1.3 Call initiation - UE-originating case . 145
5.1.3.1 Initial INVITE request . 145
5.1.4 Call initiation - UE-terminating case . 148
5.1.4.1 Initial INVITE request . 148
5.1.4.2 Reliable 18x Policy . 151
5.1.4A Session modification . 152
5.1.4A.0 General . 152
5.1.4A.1 Generating session modification request . 152
5.1.4A.2 Receiving session modification request . 153
5.1.5 Call release. 153
5.1.5A Precondition disabling policy . 153
5.1.6 Emergency service . 154
5.1.6.1 General . 154
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5.1.6.2 Initial emergency registration. 155
5.1.6.2A New initial emergency registration . 156
5.1.6.3 Initial subscription to the registration-state event package . 156
5.1.6.4 User-initiated emergency reregistration . 156
5.1.6.5 Authentication . 157
5.1.6.6 User-initiated emergency deregistration . 157
5.1.6.7 Network-initiated emergency deregistration . 157
5.1.6.8 Emergency session setup . 157
5.1.6.8.1 General . 157
5.1.6.8.2 Emergency session set-up in case of no registration . 158
5.1.6.8.3 Emergency session set-up within an emergency registration . 160
5.1.6.8.4 Emergency session setup within a non-emergency registration . 162
5.1.6.9 Emergency session release . 164
5.1.6.10 Successful or provisional response to a request not detected by the UE as relating to an

emergency session . 164
5.1.6.11 eCall type of emergency service . 165
5.1.6.11.1 General . 165
5.1.6.11.2 Initial INVITE request . 165
5.1.6.11.3 Transfer of an updated MSD . 167
5.1.6.12 Current location discovery during an emergency call . 168
5.1.6.12.1 General . 168
5.1.6.12.2 Current location information requested . 168
5.1.6.12.3 Providing current location information . 168
5.1.6A Test eCall . 168
5.1.6B Transfer of an updated MSD for PSAP Callback . 171
5.1.7 Void . 171
5.1.8 Void . 171
5.1.9 P-CSCF addresses management . 171
5.2 Procedures at the P-CSCF . 172
5.2.1 General . 172
5.2.2 Registration . 176
5.2.2.1 General . 176
5.2.2.2 IMS AKA as a security mechanism . 182
5.2.2.3 SIP digest without TLS as a security mechanism . 186
5.2.2.4 SIP digest with TLS as a security mechanism. 187
5.2.2.5 NASS-IMS bundled authentication as a security mechanism . 188
5.2.2.6 GPRS-IMS-Bundled authentication as a security mechanism . 189
5.2.2.7 P-CSCF reconfigured to not accept registrations . 189
5.2.3 Subscription to the user's registration-state event package . 189
5.2.3A Void . 191
5.2.3B SUBSCRIBE request . 191
5.2.4 Registration of multiple public user identities . 191
5.2.5 Deregistration . 193
5.2.5.1 User-initiated deregistration . 193
5.2.5.2 Network-initiated deregistration . 194
5.2.6 General treatment for all dialogs and standalone transactions excluding the REGISTER method . 194
5.2.6.1 Introduction . 194
5.2.6.2 Determination of UE-originated or UE-terminated case . 194
5.2.6.3 Requests initiated by the UE . 195
5.2.6.3.1 General for all requests . 195
5.2.6.3.2 General for all responses . 196
5.2.6.3.2A Abnormal cases . 197
5.2.6.3.3 Initial request for a dialog . 197
5.2.6.3.4 Responses to an initial request for a dialog . 200
5.2.6.3.5 Target refresh request for a dialog . 200
5.2.6.3.6 Responses to a target refresh request for a dialog . 201
5.2.6.3.7 Request for a standalone transaction . 201
5.2.6.3.8 Responses to a request for a standalone transaction . 203
5.2.6.3.9 Subsequent request other than a target refresh request . 203
5.2.6.3.10 Responses to a subsequent request other than a target refresh request . 204
5.2.6.3.11 Request for an unknown method that does not relate to an existing dialog . 204
5.2.6.3.12 Responses to a request for an unknown method that does not relate to an existing dialog . 206
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5.2.6.4 Requests terminated by the UE . 206
5.2.6.4.1 General for all requests . 206
5.2.6.4.2 General for all responses . 206
5.2.6.4.3 Initial request for a dialog . 207
5.2.6.4.4 Responses to an initial request for a dialog . 208
5.2.6.4.5 Target refresh request for a dialog . 209
5.2.6.4.6 Responses to a target refresh request for a dialog . 210
5.2.6.4.7 Request for a standalone transaction . 211
5.2.6.4.8 Responses to a request for a standalo
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