ETSI TS 124 301 V19.6.0 (2026-03)

Universal Mobile Telecommunications System (UMTS); LTE; 5G; Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 (3GPP TS 24.301 version 19.6.0 Release 19)

RTS/TSGC-0124301vj60

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
Universal Mobile Telecommunications System (UMTS);
LTE;
5G;
Non-Access-Stratum (NAS)
protocol for Evolved Packet System (EPS);
Stage 3
(3GPP TS 24.301 version 19.6.0 Release 19)

3GPP TS 24.301 version 19.6.0 Release 19 1 ETSI TS 124 301 V19.6.0 (2026-03)

Reference
RTS/TSGC-0124301vj60
Keywords
5G,LTE,UMTS
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ETSI
3GPP TS 24.301 version 19.6.0 Release 19 2 ETSI TS 124 301 V19.6.0 (2026-03)
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ETSI
3GPP TS 24.301 version 19.6.0 Release 19 3 ETSI TS 124 301 V19.6.0 (2026-03)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 21
1 Scope . 22
2 References . 22
3 Definitions and abbreviations . 26
3.1 Definitions . 26
3.2 Abbreviations . 34
4 General . 35
4.1 Overview . 35
4.2 Linkage between the protocols for EPS mobility management and EPS session management . 36
4.2A Handling of NAS signalling low priority indication . 36
4.3 UE mode of operation . 37
4.3.1 General . 37
4.3.2 Change of UE mode of operation . 38
4.3.2.1 General . 38
4.3.2.2 Change of UE's usage setting . 40
4.3.2.3 Change of voice domain preference for E-UTRAN . 41
4.3.2.4 Change or determination of IMS registration status . 42
4.3.2.5 Change of configuration regarding the use of SMS. . 43
4.4 NAS security . 43
4.4.1 General . 43
4.4.2 Handling of EPS security contexts . 44
4.4.2.1 General . 44
4.4.2.2 Establishment of a mapped EPS security context during intersystem handover . 45
4.4.2.3 Establishment of secure exchange of NAS messages . 46
4.4.2.4 Change of security keys . 48
4.4.2.5 Derivation of keys at CS to PS SRVCC handover from A/Gb mode to S1 mode or from Iu mode
to S1 mode . 49
4.4.3 Handling of NAS COUNT and NAS sequence number . 50
4.4.3.1 General . 50
4.4.3.2 Replay protection . 51
4.4.3.3 Integrity protection and verification . 51
4.4.3.4 Ciphering and deciphering . 51
4.4.3.5 NAS COUNT wrap around . 52
4.4.4 Integrity protection of NAS signalling messages. 52
4.4.4.1 General . 52
4.4.4.2 Integrity checking of NAS signalling messages in the UE . 53
4.4.4.3 Integrity checking of NAS signalling messages in the MME . 53
4.4.5 Ciphering of NAS signalling messages . 55
4.5 Disabling and re-enabling of UE's E-UTRA capability . 56
4.6 Applicability of procedures . 59
4.6.1 Relay nodes . 59
4.7 EPS mobility management and EPS session management in NB-S1 mode . 59
4.8 EPS mobility management and EPS session management in WB-S1 mode for IoT . 60
4.8.1 UE not using satellite E-UTRAN access . 60
4.8.2 UE using satellite E-UTRAN access . 60
4.9 Disabling and re-enabling of UE's NB-IoT capability . 61
4.9A Disabling and re-enabling of UE's satellite E-UTRAN capability . 62
4.10 Support of MUSIM features . 62
4.11 Satellite access for EPS . 62
4.11.1 General . 62
4.11.2 Handling list of "PLMNs not allowed to operate at the present UE location" . 63
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4.11.3 Handling multiple tracking area codes from the lower layers. 64
4.11.4 Support for enhanced discontinuous coverage . 64
4.11.5 Support for store and forward (S&F) satellite operation. 66
4.11.5.1 General . 66
4.11.5.2 Handling of timers . 66
4.11.5.3 Handling of S&F monitoring list and estimated S&F uplink delivery time duration . 67
4.12 MINT-EPS for UE to obtain service in EPS under disaster condition . 68
5 Elementary procedures for EPS mobility manage ment . 69
5.1 Overview . 69
5.1.1 General . 69
5.1.2 Types of EMM procedures . 70
5.1.3 EMM sublayer states . 71
5.1.3.1 General . 71
5.1.3.2 EMM sublayer states in the UE. 71
5.1.3.2.1 General . 71
5.1.3.2.2 Main states . 71
5.1.3.2.3 Substates of state EMM-DEREGISTERED . 73
5.1.3.2.4 Substates of state EMM-REGISTERED . 74
5.1.3.3 EPS update status . 75
5.1.3.4 EMM sublayer states in the MME . 76
5.1.3.4.1 EMM-DEREGISTERED. 76
5.1.3.4.2 EMM-COMMON-PROCEDURE-INITIATED . 76
5.1.3.4.3 EMM-REGISTERED . 76
5.1.3.4.4 EMM-DEREGISTERED-INITIATED . 76
5.1.4 Coordination between EMM and GMM . 77
5.1.5 Coordination between EMM and MM . 78
5.2 Behaviour of the UE in state EMM-DEREGISTERED and state EMM-REGISTERED . 78
5.2.1 General . 78
5.2.2 UE behaviour in state EMM-DEREGISTERED . 78
5.2.2.1 General . 78
5.2.2.2 Primary substate selection . 79
5.2.2.2.1 Selection of the substate after power on . 79
5.2.2.3 Detailed description of UE behaviour in state EMM-DEREGISTERED . 79
5.2.2.3.1 NORMAL-SERVICE . 79
5.2.2.3.2 LIMITED-SERVICE . 79
5.2.2.3.3 ATTEMPTING-TO-ATTACH . 79
5.2.2.3.4 PLMN-SEARCH . 80
5.2.2.3.5 NO-IMSI . 80
5.2.2.3.6 ATTACH-NEEDED . 81
5.2.2.3.7 NO-CELL-AVAILABLE . 81
5.2.2.3.8 eCALL-INACTIVE . 81
5.2.2.4 Substate when back to state EMM-DEREGISTERED from another EMM state . 81
5.2.3 UE behaviour in state EMM-REGISTERED . 82
5.2.3.1 General . 82
5.2.3.2 Detailed description of UE behaviour in state EMM-REGISTERED . 82
5.2.3.2.1 NORMAL-SERVICE . 82
5.2.3.2.2 ATTEMPTING-TO-UPDATE . 82
5.2.3.2.3 LIMITED-SERVICE . 84
5.2.3.2.4 PLMN-SEARCH . 84
5.2.3.2.5 UPDATE-NEEDED . 84
5.2.3.2.6 NO-CELL-AVAILABLE . 84
5.2.3.2.7 ATTEMPTING-TO-UPDATE-MM. 85
5.2.3.2.8 IMSI-DETACH-INITIATED . 85
5.3 General on elementary EMM procedures . 85
5.3.1 EMM modes and NAS signalling connection . 85
5.3.1.1 Establishment of the NAS signalling connection . 85
5.3.1.2 Release of the NAS signalling connection . 87
5.3.1.2.1 General . 87
5.3.1.2.2 UE is using EPS services with control plane CIoT EPS optimization . 91
5.3.1.3 Suspend and resume of the NAS signalling connection . 91
5.3.2 Lists of forbidden tracking areas . 92
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5.3.3 List of forbidden PLMNs for attach in S101 mode . 92
5.3.3a Forbidden PLMNs for EPS services . 93
5.3.4 Equivalent PLMNs list. 93
5.3.5 Handling of the periodic tracking area update timer and mobile reachable timer (S1 mode only) . 93
5.3.6 Handling of timer T3402 . 95
5.3.7 Handling of the Local Emergency Numbers List and the Extended Local Emergency Numbers List . 95
5.3.7a Specific requirements for UE configured to use timer T3245 . 96
5.3.7b Specific requirements for UE when receiving non-integrity protected reject messages . 97
5.3.8 Abnormal cases in the UE . 100
5.3.9 Handling of NAS level mobility management congestion control . 101
5.3.9A Handling of congestion control for transport of user data via the control plane . 102
5.3.10 Access class control . 102
5.3.11 Power saving mode . 103
5.3.12 Extended idle-mode DRX cycle . 104
5.3.13 Interaction between power saving mode and extended idle mode DRX cycle . 104
5.3.14 Dedicated core network . 104
5.3.15 CIoT EPS optimizations . 105
5.3.16 Restriction on use of enhanced coverage . 107
5.3.17 Service Gap Control. 107
5.3.18 Restricted local operator services . 109
5.3.19 Core Network selection and redirection for UEs using CIoT optimizations. 109
5.3.19.1 Core network selection . 109
5.3.19.2 Redirection of the UE by the core network . 109
5.3.20 UE radio capability signalling optimisatio n . 110
5.3.21 Wake-up signal assistance . 111
5.3.22 Void . 112
5.3.23 Control of UE access technology utilization by EPS . 112
5.3.23.1 General . 112
5.3.23.2 List of PLMNs with associated access technology restrictions . 112
5.4 EMM common procedures . 112
5.4.1 GUTI reallocation procedure . 112
5.4.1.1 General . 112
5.4.1.2 GUTI reallocation initiation by the network . 113
5.4.1.3 GUTI reallocation completion by the UE . 113
5.4.1.4 GUTI reallocation completion by the network . 114
5.4.1.5 Abnormal cases in the UE . 114
5.4.1.6 Abnormal cases on the network side . 114
5.4.2 Authentication procedure . 116
5.4.2.1 General . 116
5.4.2.2 Authentication initiation by the network . 116
5.4.2.3 Authentication response by the UE . 117
5.4.2.4 Authentication completion by the network . 118
5.4.2.5 Authentication not accepted by the network . 118
5.4.2.6 Authentication not accepted by the UE . 119
5.4.2.7 Abnormal cases . 119
5.4.3 Security mode control procedure . 124
5.4.3.1 General . 124
5.4.3.2 NAS security mode control initiation by the network . 125
5.4.3.3 NAS security mode command accepted by the UE . 128
5.4.3.4 NAS security mode control completion by the network . 129
5.4.3.5 NAS security mode command not accepted by the UE. 130
5.4.3.6 Abnormal cases in the UE . 130
5.4.3.7 Abnormal cases on the network side . 130
5.4.4 Identification procedure . 131
5.4.4.1 General . 131
5.4.4.2 Identification initiation by the network . 131
5.4.4.3 Identification response by the UE . 132
5.4.4.4 Identification completion by the network . 132
5.4.4.5 Abnormal cases in the UE . 132
5.4.4.6 Abnormal cases on the network side . 132
5.4.5 EMM information procedure . 133
5.4.5.1 General . 133
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5.4.5.2 EMM information procedure initiation by the network . 133
5.4.5.3 EMM information procedure in the UE . 134
5.4.5.4 Abnormal cases on the network side . 134
5.5 EMM specific procedures . 134
5.5.1 Attach procedure . 134
5.5.1.1 General . 134
5.5.1.2 Attach procedure for EPS services . 136
5.5.1.2.1 General . 136
5.5.1.2.2 Attach procedure initiation . 136
5.5.1.2.3 EMM common procedure initiation . 142
5.5.1.2.4 Attach accepted by the network . 142
5.5.1.2.4A Attach successful for EPS services and not accepted for SMS services . 151
5.5.1.2.5 Attach not accepted by the network . 152
5.5.1.2.5A Attach for emergency bearer services not accepted by the network . 161
5.5.1.2.5B Attach for initiating a PDN connection for emergency bearer services not accepted by the
network . 163
5.5.1.2.5B1 Attach by a UE transferring an emergency PDU session using a standalone PDN
CONNECTIVITY REQUEST message . 163
5.5.1.2.5C Attach for access to RLOS not accepted by the network . 164
5.5.1.2.6 Abnormal cases in the UE . 164
5.5.1.2.6A Abnormal cases in the UE, SMS services not accepted . 168
5.5.1.2.7 Abnormal cases on the network side . 169
5.5.1.3 Combined attach procedure for EPS services and non-EPS services (S1 mode only) . 170
5.5.1.3.1 General . 170
5.5.1.3.2 Combined attach procedure initiation . 171
5.5.1.3.3 EMM common procedure initiation . 171
5.5.1.3.4 Combined attach accepted by the network . 171
5.5.1.3.5 Combined attach not accepted by the network . 174
5.5.1.3.6 Abnormal cases in the UE . 180
5.5.1.3.7 Abnormal cases on the network side . 181
5.5.2 Detach procedure . 181
5.5.2.1 General . 181
5.5.2.2 UE initiated detach procedure . 182
5.5.2.2.1 UE initiated detach procedure initiation . 182
5.5.2.2.2 UE initiated detach procedure completion for EPS services only . 183
5.5.2.2.3 UE initiated combined detach procedure completion . 184
5.5.2.2.4 Abnormal cases in the UE . 184
5.5.2.2.5 Abnormal cases on the network side . 186
5.5.2.3 Network initiated detach procedure . 186
5.5.2.3.1 Network initiated detach procedure initiation . 186
5.5.2.3.2 Network initiated detach procedure completion by the UE . 188
5.5.2.3.3 Network initiated detach procedure completion by the network . 194
5.5.2.3.4 Abnormal cases in the UE . 194
5.5.2.3.5 Abnormal cases on the network side . 194
5.5.3 Tracking area updating procedure (S1 mode only) . 196
5.5.3.1 General . 196
5.5.3.2 Normal and periodic tracking area updating procedure . 198
5.5.3.2.1 General . 198
5.5.3.2.2 Normal and periodic tracking area updating procedure initiation . 198
5.5.3.2.3 EMM common procedure initiation . 207
5.5.3.2.4 Normal and periodic tracking area updating procedure accepted by the network . 207
5.5.3.2.4A Tracking area updating successful for EPS services and not accepted for SMS services . 222
5.5.3.2.5 Normal and periodic tracking area updating procedure not accepted by the network . 223
5.5.3.2.5A Tracking area updating procedure for initiating a PDN connection for emergency bearer
services not accepted by the network . 233
5.5.3.2.5B Tracking area updating for access to RLOS not accepted by the network . 234
5.5.3.2.6 Abnormal cases in the UE . 235
5.5.3.2.6A Abnormal cases in the UE, SMS services not accepted . 241
5.5.3.2.7 Abnormal cases on the network side . 241
5.5.3.3 Combined tracking area updating procedure . 244
5.5.3.3.1 General . 244
5.5.3.3.2 Combined tracking area updating procedure initiation . 244
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5.5.3.3.3 EMM common procedure initiation . 247
5.5.3.3.4 Combined tracking area updating procedure accepted by the network . 247
5.5.3.3.5 Combined tracking area updating procedure not accepted by the network . 250
5.5.3.3.6 Abnormal cases in the UE . 258
5.5.3.3.7 Abnormal cases on the network side . 260
5.5.4 eCall inactivity procedure . 260
5.5.5 Tracking area update request message (for N1 mode only) . 260
5.5.6 Attach request message (for N1 mode only) . 261
5.6 EMM connection management procedures (S1 mode only) . 261
5.6.1 Service request procedure . 261
5.6.1.1 General . 261
5.6.1.2 Service request procedure initiation . 267
5.6.1.2.0A General . 267
5.6.1.2.1 UE is not using EPS services with control plane CIoT EPS optimization . 267
5.6.1.2.2 UE is using EPS services with control plane CIoT EPS optimization . 268
5.6.1.2.3 UE is using EPS services with control plane CIoT EPS optimization with overhead reduction . 269
5.6.1.3 EMM common procedure initiation . 269
5.6.1.4 Service request procedure accepted by the network . 269
5.6.1.4.1 UE is not using EPS services with control plane CIoT EPS optimization . 269
5.6.1.4.2 UE is using EPS services with control plane CIoT EPS optimization . 272
5.6.1.4.3
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