ETSI TS 124 501 V19.6.2 (2026-03)

5G; Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3 (3GPP TS 24.501 version 19.6.2 Release 19)

RTS/TSGC-0124501vj62

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: 23-Mar-2026

Standards Content (Sample)

ETSI TS 124 501 V19.6.2 (2026-04)

TECHNICAL SPECIFICATION
5G;
Non-Access-Stratum (NAS) protocol for 5G System (5GS);
Stage 3
(3GPP TS 24.501 version 19.6.2 Release 19)

3GPP TS 24.501 version 19.6.2 Release 19 1 ETSI TS 124 501 V19.6.2 (2026-04)

Reference
RTS/TSGC-0124501vj62
Keywords
5G
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3GPP TS 24.501 version 19.6.2 Release 19 2 ETSI TS 124 501 V19.6.2 (2026-04)
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ETSI
3GPP TS 24.501 version 19.6.2 Release 19 3 ETSI TS 124 501 V19.6.2 (2026-04)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 27
1 Scope . 28
2 References . 28
3 Definitions and abbreviations . 33
3.1 Definitions . 33
3.2 Abbreviations . 46
4 General . 49
4.1 Overview . 49
4.2 Coordination between the protocols for 5GS mobility management and 5GS session management . 50
4.2A Control of UE access technology utilization by 5GS . 51
4.2A.1 General . 51
4.2A.2 List of PLMNs with associated access technology restrictions . 51
4.3 UE domain selection . 52
4.3.1 UE's usage setting . 52
4.3.2 Domain selection for UE originating sessions / calls . 52
4.3.3 Change of UE's usage setting . 54
4.3.4 Change or determination of IMS voice availability . 54
4.4 NAS security . 55
4.4.1 General . 55
4.4.2 Handling of 5G NAS security contexts. 55
4.4.2.1 General . 55
4.4.2.1.1 Establishment of 5G NAS security context . 55
4.4.2.1.2 UE leaving state 5GMM-DEREGISTERED . 58
4.4.2.1.3 UE entering state 5GMM-DEREGISTERED . 58
4.4.2.2 Establishment of a mapped 5G NAS security context during inter-system change from S1 mode
to N1 mode in 5GMM-CONNECTED mode . 58
4.4.2.3 Establishment of a 5G NAS security context during N1 mode to N1 mode handover . 59
4.4.2.4 Establishment of an EPS security context during inter-system change from N1 mode to S1 mode
in 5GMM-CONNECTED mode . 60
4.4.2.5 Establishment of secure exchange of NAS messages . 61
4.4.2.6 Change of security keys . 63
4.4.3 Handling of NAS COUNT and NAS sequence number . 63
4.4.3.1 General . 63
4.4.3.2 Replay protection . 64
4.4.3.3 Integrity protection and verification . 64
4.4.3.4 Ciphering and deciphering . 65
4.4.3.5 NAS COUNT wrap around . 65
4.4.4 Integrity protection of NAS signalling messages. 66
4.4.4.1 General . 66
4.4.4.2 Integrity checking of NAS signalling messages in the UE . 66
4.4.4.3 Integrity checking of NAS signalling messages in the AMF . 67
4.4.5 Ciphering of NAS signalling messages . 69
4.4.6 Protection of initial NAS signalling messages . 69
4.4.7 Protection of NAS IEs . 71
4.5 Unified access control . 72
4.5.1 General . 72
4.5.2 Determination of the access identities and access category associated with a request for access for
UEs not operating in SNPN access operation mode over 3GPP access . 74
4.5.2A Determination of the access identities and access category associated with a request for access for
UEs operating in SNPN access operation mode over 3GPP access . 80
4.5.3 Operator-defined access categories . 86
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4.5.4 Access control and checking . 88
4.5.4.1 Access control and checking in 5GMM-IDLE mode and in 5GMM-IDLE mode with suspend

indication . 88
4.5.4.2 Access control and checking in 5GMM-CONNECTED mode and in 5GMM-CONNECTED
mode with RRC inactive indication . 90
4.5.5 Exception handling and avoiding double barring . 92
4.5.6 Mapping between access categories/access identities and RRC establishment cause . 97
4.6 Network slicing . 98
4.6.1 General . 98
4.6.2 Mobility management aspects. 101
4.6.2.1 General . 101
4.6.2.2 NSSAI storage . 103
4.6.2.3 Provision of NSSAI to lower layers in 5GMM-IDLE mode . 110
4.6.2.4 Network slice-specific authentication and authorization . 112
4.6.2.5 Mobility management-based network slice admission control . 114
4.6.2.6 Provision of NSAG information to lower layers . 115
4.6.2.7 Mobility management-based network slice replacement . 116
4.6.2.8 Mobility management for optimised handling of temporarily available network slices . 117
4.6.2.9 Mobility management based network slice usage control . 119
4.6.2.10 Mobility management aspects of handling network slices with NS-AoS not matching deployed

tracking areas . 120
4.6.2.11 Mobility management for partial network slice . 121
4.6.3 Session management aspects . 122
4.6.3.0 General . 122
4.6.3.1 Session management based network slice admission control . 122
4.6.3.2 Support of network slice admission control and interworking with EPC . 123
4.6.3.3 Session management based network slice data rate limitation control . 123
4.6.3.4 Session management based network slice replacement . 123
4.6.3.5 Session management for optimized handling of temporarily available network slices . 124
4.6.3.6 Session management for partial network slice . 125
4.6.3.7 Session management aspect of handling network slices with NS-AoS not matching deployed
tracking areas . 126
4.7 NAS over non-3GPP access . 127
4.7.1 General . 127
4.7.2 5GS mobility management aspects . 127
4.7.2.1 General . 127
4.7.2.2 Establishment cause for non-3GPP access . 128
4.7.3 5GS session management aspects . 129
4.7.4 Limited service state over non-3GPP access . 129
4.7.5 NAS signalling using trusted WLAN access network . 130
4.8 Interworking with E-UTRAN connected to EPC . 130
4.8.1 General . 130
4.8.2 Single-registration mode . 131
4.8.2.1 General . 131
4.8.2.2 Single-registration mode with N26 interface . 131
4.8.2.3 Single-registration mode without N26 interface . 131
4.8.2.3.1 Interworking between NG-RAN and E-UTRAN . 131
4.8.2.3.2 Interworking between TNGF or N3IWF connected to 5GCN and E-UTRAN. 133
4.8.3 Dual-registration mode . 134
4.8.4 Core Network selection for UEs not using CIoT 5GS optimizations . 135
4.8.4A Core Network selection and redirection for UEs using CIoT optimizations. 135
4.8.4A.1 Core network selection . 135
4.8.4A.2 Redirection of the UE by the core network . 136
4.9 Disabling and re-enabling of UE's N1 mode capability . 136
4.9.1 General . 136
4.9.2 Disabling and re-enabling of UE's N1 mode capability for 3GPP access . 136
4.9.3 Disabling and re-enabling of UE's N1 mode capability for non-3GPP access. 140
4.9.4 Disabling and re-enabling of UE's satellite NG-RAN capability . 141
4.10 Interworking with ePDG connected to EPC . 141
4.11 UE configuration parameter updates . 142
4.12 Access traffic steering, switching and splitting (ATSSS) . 142
4.13 Support of NAS signalling using wireline access network . 142
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4.14 Non-public network (NPN) . 144
4.14.1 General . 144
4.14.2 Stand-alone non-public network (SNPN) . 144
4.14.3 Public network integrated non-public network (PNI-NPN) . 146
4.15 Time synchronization and time sensitive communication . 148
4.15.1 General . 148
4.15.2 Void . 148
4.15.2.1 Void. 148
4.15.2.2 Void. 148
4.15.2.3 Void. 148
4.15.3 Time synchronization . 148
4.15.4 User plane node management . 148
4.16 UE radio capability signalling optimisation . 149
4.17 5GS mobility management in NB-N1 mode . 150
4.18 5GS session management in NB-N1 mode . 150
4.19 5GS mobility management in WB-N1 mode for IoT . 151
4.20 5GS session management in WB-N1 mode for IoT . 151
4.21 Authentication and key management for applications (AKMA) . 152
4.22 Uncrewed aerial vehicle identification, authentication, authorization and operational restrictions . 152
4.22.1 General . 152
4.22.2 Authentication and authorization of UAV . 152
4.22.3 Authorization of C2 communication . 153
4.22.4 Void . 154
4.22.5 Support of no-transmit zone (NTZ) . 154
4.23 NAS over Non-Terrestrial Network . 154
4.23.1 General . 154
4.23.2 List of "PLMNs not allowed to operate at the present UE location" . 154
4.23.3 5GS mobility management via a satellite NG-RAN cell . 155
4.23.4 5GS session management via a satellite NG-RAN cell . 156
4.23.5 Handling multiple tracking area codes from the lower layers. 156
4.24 Minimization of service interruption . 157
4.25 Support of MUSIM features . 159
4.26 Support for Personal IoT Network service . 159
4.27 Mobile base station relay support . 160
4.28 NAS-specific aspects of mobile gNB with wireless access backhauling (MWAB) . 160
4.28.1 General . 160
4.28.2 Authorization of MWAB-UE . 161
4.28.3 Control of UE access via MWAB . 161
4.29 Support of indirect network sharing . 161
4.30 QoS differentiation of traffic for non-3GPP device identifier . 163
5 Elementary procedures for 5GS mobility management . 164
5.1 Overview . 164
5.1.1 General . 164
5.1.2 Types of 5GMM procedures . 164
5.1.3 5GMM sublayer states . 165
5.1.3.1 General . 165
5.1.3.2 5GMM sublayer states . 165
5.1.3.2.1 5GMM sublayer states in the UE. 165
5.1.3.2.1.1 General . 165
5.1.3.2.1.2 Main states . 166
5.1.3.2.1.2.1 5GMM-NULL . 166
5.1.3.2.1.2.2 5GMM-DEREGISTERED . 166
5.1.3.2.1.2.3 5GMM-REGISTERED-INITIATED . 166
5.1.3.2.1.2.4 5GMM-REGISTERED . 166
5.1.3.2.1.2.5 5GMM-DEREGISTERED-INITIATED . 166
5.1.3.2.1.2.6 5GMM-SERVICE-REQUEST-INITIATED. 166
5.1.3.2.1.3 Substates of state 5GMM-DEREGISTERED . 167
5.1.3.2.1.3.1 General . 167
5.1.3.2.1.3.2 5GMM-DEREGISTERED.NORMAL-SERVICE . 167
5.1.3.2.1.3.3 5GMM-DEREGISTERED.LIMITED-SERVICE . 167
5.1.3.2.1.3.4 5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION . 167
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5.1.3.2.1.3.5 5GMM-DEREGISTERED.PLMN-SEARCH . 167
5.1.3.2.1.3.6 5GMM-DEREGISTERED.NO-SUPI . 167
5.1.3.2.1.3.7 5GMM-DEREGISTERED.NO-CELL-AVAILABLE . 167
5.1.3.2.1.3.8 5GMM-DEREGISTERED.eCALL-INACTIVE . 168
5.1.3.2.1.3.9 5GMM-DEREGISTERED.INITIAL-REGISTRATION-NEEDED . 168
5.1.3.2.1.4 Substates of state 5GMM-REGISTERED . 168
5.1.3.2.1.4.1 General . 168
5.1.3.2.1.4.2 5GMM-REGISTERED.NORMAL-SERVICE . 168
5.1.3.2.1.4.3 5GMM-REGISTERED.NON-ALLOWED-SERVICE . 168
5.1.3.2.1.4.4 5GMM-REGISTERED.ATTEMPTING-REGISTRATION-UPDATE . 168
5.1.3.2.1.4.5 5GMM-REGISTERED.LIMITED-SERVICE . 169
5.1.3.2.1.4.6 5GMM-REGISTERED.PLMN-SEARCH . 169
5.1.3.2.1.4.7 5GMM-REGISTERED.NO-CELL-AVAILABLE . 169
5.1.3.2.1.4.8 5GMM-REGISTERED.UPDATE-NEEDED . 169
5.1.3.2.2 5GS update status in the UE . 170
5.1.3.2.3 5GMM sublayer states in the network side . 170
5.1.3.2.3.1 General . 170
5.1.3.2.3.2 5GMM-DEREGISTERED . 171
5.1.3.2.3.3 5GMM-COMMON-PROCEDURE-INITIATED . 171
5.1.3.2.3.4 5GMM-REGISTERED . 171
5.1.3.2.3.5 5GMM-DEREGISTERED-INITIATED . 171
5.1.4 Coordination between 5GMM and EMM . 171
5.1.4.1 General . 171
5.1.4.2 Coordination between 5GMM for 3GPP access and EMM with N26 interface . 172
5.1.4.3 Coordination between 5GMM for 3GPP access and EMM without N26 interface . 172
5.1.5 Coordination between 5GMM and GMM . 173
5.2 Behaviour of the UE in state 5GMM-DEREGISTERED and state 5GMM-REGISTERED . 173
5.2.1 General . 173
5.2.2 UE behaviour in state 5GMM-DEREGISTERED . 173
5.2.2.1 General . 173
5.2.2.2 Primary substate selection . 173
5.2.2.2.1 Selection of the substate after power on . 173
5.2.2.3 Detailed description of UE behaviour in state 5GMM-DEREGISTERED . 174
5.2.2.3.1 NORMAL-SERVICE . 174
5.2.2.3.2 LIMITED-SERVICE . 174
5.2.2.3.3 ATTEMPTING-REGISTRATION . 174
5.2.2.3.4 PLMN-SEARCH . 176
5.2.2.3.5 NO-SUPI . 176
5.2.2.3.6 NO-CELL-AVAILABLE . 176
5.2.2.3.7 eCALL-INACTIVE . 176
5.2.2.3.8 INITIAL-REGISTRATION-NEEDED . 177
5.2.2.4 Substate when back to state 5GMM-DEREGISTERED from another 5GMM state . 177
5.2.3 UE behaviour in state 5GMM-REGISTERED . 177
5.2.3.1 General . 177
5.2.3.2 Detailed description of UE behaviour in state 5GMM-REGISTERED . 177
5.2.3.2.1 NORMAL-SERVICE . 177
5.2.3.2.2 NON-ALLOWED-SERVICE . 178
5.2.3.2.3 ATTEMPTING-REGISTRATION-UPDATE . 178
5.2.3.2.4 LIMITED-SERVICE . 180
5.2.3.2.5 PLMN-SEARCH . 180
5.2.3.2.6 NO-CELL-AVAILABLE . 180
5.2.3.2.7 UPDATE-NEEDED . 180
5.3 General on elementary 5GMM procedures . 181
5.3.1 5GMM modes and N1 NAS signalling connection . 181
5.3.1.1 Establishment of the N1 NAS signalling connection . 181
5.3.1.2 Re-establishment of the N1 NAS signalling connection . 183
5.3.1.3 Release of the N1 NAS signalling connection . 184
5.3.1.4 5GMM-CONNECTED mode with RRC inactive indication . 189
5.3.1.5 Suspend and resume of the N1 NAS signalling connection . 193
5.3.2 Permanent identifiers . 194
5.3.3 Temporary identities . 197
5.3.4 Registration areas . 198
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5.3.5 Service area restrictions . 199
5.3.5.1 General . 199
5.3.5.2 3GPP access service area restrictions . 199
5.3.5.3 Wireline access service area restrictions . 203
5.3.6 Mobile initiated connection only mode . 204
5.3.7 Handling of the periodic registration update timer and mobile reachable timer . 207
5.3.8 Handling of timer T3502 . 209
5.3.9 Handling of NAS level mobility management congestion control . 209
5.3.10 Handling of DNN based congestion control . 210
5.3.11 Handling of S-NSSAI based congestion control . 210
5.3.12 Handling of local emergency numbers . 211
5.3.12A Handling of local emergency numbers received via 3GPP access and non-3GPP access . 212
5.3.12A.1 General . 212
5.3.12A.2 Receiving a REGISTRATION ACCEPT message via non-3GPP access . 212
5.3.13 Lists of 5GS forbidden tracking areas. 213
5.3.13A Forbidden PLMN lists . 214
5.3.14 List of equivalent PLMNs . 215
5.3.14A List of equivalent SNPNs . 215
5.3.15 Transmission failure abnormal case in the UE . 216
5.3.15A Abnormal cases in the UE . 216
5.3.16 Extended DRX cycle for UEs in 5GMM-IDLE and 5GMM-CONNECTED mode with RRC inactive
indication . 216
5.3.17 Service Gap Control. 217
5.3.18 Restriction on use of enhanced coverage . 219
5.3.19 Handling of congestion control for transport of user data via the control plane .
...