ETSI TS 124 502 V19.3.0 (2026-03)

5G; Access to the 3GPP 5G Core Network (5GCN) via non-3GPP access networks (3GPP TS 24.502 version 19.3.0 Release 19)

RTS/TSGC-0124502vj30

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
5G;
Access to the 3GPP 5G Core Network (5GCN)
via non-3GPP access networks
(3GPP TS 24.502 version 19.3.0 Release 19)

3GPP TS 24.502 version 19.3.0 Release 19 1 ETSI TS 124 502 V19.3.0 (2026-03)

Reference
RTS/TSGC-0124502vj30
Keywords
5G
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ETSI
3GPP TS 24.502 version 19.3.0 Release 19 2 ETSI TS 124 502 V19.3.0 (2026-03)
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ETSI
3GPP TS 24.502 version 19.3.0 Release 19 3 ETSI TS 124 502 V19.3.0 (2026-03)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 8
1 Scope . 9
2 References . 9
3 Definitions, symbols and abbreviations . 11
3.1 Definitions . 11
3.2 Abbreviations . 12
4 General . 13
4.1 Overview . 13
4.2 Untrusted access . 14
4.3 Identities . 14
4.3.1 User identities . 14
4.3.2 FQDN for N3IWF Selection . 14
4.4 Quality of service support . 15
4.4.1 General . 15
4.4.2 QoS differentiation in non-3GPP access . 15
4.4.2.1 General . 15
4.4.2.2 QoS signalling . 15
4.4.2.3 QoS differentiation in user plane . 16
4.4.2.4 Reflective QoS . 16
4.4.2.5 QoS enforcement . 17
4.5 Trusted access . 17
4.6 Forbidden PLMNs for non-3GPP access to 5GCN . 17
5 Network discovery and selection . 18
5.1 General . 18
5.2 Access network discovery procedure . 18
5.2.1 General . 18
5.2.2 Discovering availability of WLAN access networks . 18
5.3 Access network selection procedure. 19
5.3.1 General . 19
5.3.2 WLAN selection procedure . 19
5.3.2.1 General . 19
5.3.2.2 Manual mode WLAN selection. 20
5.3.2.3 Automatic mode WLAN selection . 20
5.3A PLMN selection procedures using trusted non-3GPP access . 23
5.3A.1 General . 23
5.3A.2 PLMN solicitation . 23
5.3A.3 Manual PLMN selection mode procedure . 24
5.3A.4 Automatic mode PLMN selection procedure . 24
5.3A.4.1 General . 24
5.3A.4.2 Attempting to select HPLMN or equivalent HPLMN . 25
5.3A.4.3 Void. 25
5.3B PLMN selection procedures using wireline access . 25
5.3C PLMN selection procedures for 5G NSWO . 25
5.3D SNPN selection procedures using trusted non-3GPP access . 26
5.3D.1 General . 26
5.3D.2 SNPN solicitation . 26
5.3D.3 Manual SNPN selection mode procedure . 27
5.3D.4 Automatic mode SNPN selection procedure. 27
5.3D.4.1 General . 27
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5.3D.5 Automatic SNPN selection procedure for onboarding services in SNPN over trusted non-3GPP
access . 28
5.3E PLMN selection procedures using untrusted non-3GPP access . 29
5.3F SNPN selection procedures using untrusted non-3GPP access . 29
5.3G SNPN selection procedures using wireline access . 29
5.3H SNPN selection procedures for 5G NSWO . 29
5.4 Access network reselection procedure . 29
5.4.1 General . 29
5.4.2 WLAN reselection procedure . 29
6 UE - 5GC network protocols . 30
6.1 General . 30
6.2 Void . 30
6.3 Authentication and authorization for accessing 5GS via non-3GPP access network . 30
6.3.1 General . 30
6.3.2 Authentication of N5GC device behind a CRG over wireline access . 30
6.3a Authentication for 5G NSWO . 31
6.3b 5G NSWO provided by 5G-RG . 32
6.3b.1 General . 32
6.3b.2 Authentication for 5G NSWO provided by 5G-RG . 32
6.4 Handling of ANDSP Information . 33
6.4.1 General . 33
6.4.2 UE procedures . 33
6.4.2.1 General . 33
6.4.2.2 Use of WLAN selection information . 33
6.4.2.3 Use of N3AN node configuration information . 33
6.4.3 ANDSP information from the network . 33
7 Security association management procedures . 34
7.1 General . 34
7.2 N3AN node selection procedure . 34
7.2.1 General . 34
7.2.2 N3AN node configuration information . 34
7.2.3 Determination of the country the UE is located in . 35
7.2.4 N3AN node selection for non-emergency services . 35
7.2.4.1 General . 35
7.2.4.2 Determine if the visited country mandates the selection of N3IWF in this country. 36
7.2.4.3 UE procedure when the UE only supports connectivity with N3IWF . 36
7.2.4.4 UE procedure when the UE supports connectivity with N3IWF and ePDG . 40
7.2.4.4.1 General . 40
7.2.4.4.2 N3AN node selection for IMS service . 40
7.2.4.4.3 N3AN node selection for Non-IMS service . 44
7.2.5 Selection of an N3AN node in an SNPN . 48
7.2.6 N3AN node selection for emergency services . 49
7.2.6.1 General . 49
7.2.6.2 UE procedure when the UE only supports connectivity with N3IWF . 49
7.2.6.2a UE procedure when the UE only supports connectivity with N3IWF when accessing SNPN via
non-3GPP access . 50
7.2.6.3 UE procedure when the UE supports connectivity with N3IWF and ePDG . 50
7.2.7 N3AN node selection based on N3IWF identifier information provided to the UE in the
REGISTRATION REJECT message . 51
7.2.8 N3IWF selection for onboarding SNPN . 51
7.3 IKE SA establishment procedure for untrusted non-3GPP access . 52
7.3.1 General . 52
7.3.2 IKE SA and signalling IPsec SA establishment procedure . 52
7.3.2.1 IKE SA and signalling IPsec SA establishment initiation . 52
7.3.2.2 IKE SA and signalling IPsec SA establishment accepted by the network . 53
7.3.2.3 IKE SA and signalling IPsec SA establishment not accepted by the network . 55
7.3.3 EAP-5G session over non-3GPP access . 56
7.3.3.1 General . 56
7.3.3.1A EAP-5G session initiation . 56
7.3.3.2 EAP-5G session completion initiated by the network . 57
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7.3.3.3 EAP-5G session completion initiated by the UE . 58
7.3.4 Abnormal cases in the UE . 59
7.3.5 Abnormal cases in the N3IWF . 59
7.3.6 Procedures for UE behind the 5G-RG accessing 5GC via untrusted non-3GPP access network . 59
7.3A IKE SA establishment procedure for trusted non-3GPP access . 60
7.3A.1 General . 60
7.3A.2 EAP session over non-3GPP access . 61
7.3A.2.1 General . 61
7.3A.2.2 Identity transaction . 62
7.3A.2.3 EAP-5G session initiation . 62
7.3A.2.4 EAP-5G session completion initiated by the network . 63
7.3A.2.5 EAP-5G session completion initiated by the UE . 63
7.3A.3 IKE SA and signalling IPsec SA establishment procedure . 63
7.3A.3.1 IKE SA and signalling IPsec SA establishment initiation . 63
7.3A.3.2 IKE SA and signalling IPsec SA establishment accepted by the network . 64
7.3A.3.3 IKE SA and signalling IPsec SA establishment not accepted by the network . 64
7.3A.4 Procedure for devices without NAS support . 64
7.3A.4.1 General . 64
7.3A.4.2 N5CW device registration over trusted WLAN access network . 64
7.3A.4.3 Re-authentication procedure for the N5CW device mobility between two TWAPs connected to

the same TWIF . 65
7.3A.5 TNAN selection based on TNAN information provided to the UE in the REGISTRATION REJECT
message . 65
7.3A.6 Procedures for UE behind the 5G-RG accessing 5GC via trusted non-3GPP access network . 66
7.3A.7 Re-authentication procedure for the UE mobility between two TNAPs connected to the same TNGF . 66
7.4 IKEv2 SA deletion procedure . 66
7.4.1 General . 66
7.4.2 IKE SA deletion procedure initiated by the N3IWF and the TNGF . 67
7.4.2.1 IKE SA deletion initiation . 67
7.4.2.2 IKE SA deletion accepted by the UE . 67
7.4.2.3 Abnormal cases in the N3IWF and the TNGF . 67
7.4.3 IKE SA deletion procedure initiated by the UE . 67
7.4.3.1 IKE SA deletion initiation . 67
7.4.3.2 IKE SA deletion accepted by the N3IWF and the TNGF . 68
7.4.3.3 Abnormal cases in the UE . 68
7.5 User plane IPsec SA creation procedure . 68
7.5.1 General . 68
7.5.2 Child SA creation procedure initiation . 68
7.5.3 Child SA creation procedure accepted by the UE . 69
7.5.4 Child SA creation procedure not accepted by the UE . 69
7.5.5 Abnormal cases in the UE . 70
7.5.6 Abnormal cases in the N3IWF and the TNGF . 70
7.6 IPsec SA modification procedure . 70
7.6.1 General . 70
7.6.2 N3IWF and TNGF procedure for IPsec child SA modification . 70
7.6.3 UE procedure for IPsec child SA modification. 70
7.7 IPSec SA deletion procedure . 71
7.7.1 General . 71
7.7.2 N3IWF-initated and TNGF-initiated child SA deletion procedure . 71
7.7.2.1 N3IWF-initiated and TNGF-initiated child SA deletion procedure initiation . 71
7.7.2.2 N3IWF-initiated and TNGF-initiated child SA deletion procedure accepted by the UE . 71
7.7.2.3 Abnormal cases in the N3IWF and the TNGF . 72
7.7.3 UE-initiated child SA deletion procedure . 72
7.7.3.1 UE-initiated child SA deletion procedure initiation . 72
7.7.3.2 UE-initiated child SA deletion procedure accepted by the N3IWF and the TNGF. 72
7.7.3.3 Abnormal cases in the UE . 72
7.7.4 Abnormal cases in the UE . 72
7.7.5 Abnormal cases in the N3IWF and the TNGF . 72
7.8 UE-initiated liveness check procedure . 72
7.8.1 General . 72
7.8.2 UE-initiated liveness check procedure initiation . 72
7.8.3 UE-initiated liveness check procedure completion . 73
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7.8.4 Abnormal cases . 73
7.9 Network-initiated liveness check procedure . 73
7.9.1 General . 73
7.9.2 Network-initiated liveness check procedure initiation . 73
7.9.3 Network-initiated liveness check procedure completion . 73
7.9.4 Abnormal cases . 73
7.10 IKE SA rekeying procedure . 74
7.10.1 General . 74
7.10.2 N3IWF-initiated and TNGF-initiated IKE SA rekeying procedure . 74
7.10.2.1 N3IWF-initiated and TNGF-initiated IKE SA rekeying procedure initiation . 74
7.10.2.2 N3IWF-initiated and TNGF-initiated IKE SA rekeying procedure completion . 74
7.10.2.3 Abnormal cases . 74
7.10.3 UE-initiated IKE SA rekeying procedure . 75
7.10.3.1 UE-initiated IKE SA rekeying procedure initiation . 75
7.10.3.2 UE-initiated IKE SA rekeying procedure completion . 75
7.10.3.3 Abnormal cases . 75
7.11 IPsec SA rekeying procedure . 75
7.11.1 General . 75
7.11.2 N3IWF-initiated and TNGF-initiated IPsec SA rekeying procedure . 75
7.11.2.1 N3IWF-initiated and TNGF-initiated IPsec SA rekeying procedure initiation . 75
7.11.2.2 N3IWF-initiated and TNGF-initiated IPsec SA rekeying procedure completion . 75
7.11.2.3 Abnormal cases . 76
7.11.3 UE-initiated IPsec SA rekeying procedure . 76
7.11.3.1 UE-initiated IPsec SA rekeying procedure initiation . 76
7.11.3.2 UE-initiated IPsec SA rekeying procedure completion . 76
7.11.3.3 Abnormal cases . 76
7A void . 77
8 Message transport procedures . 77
8.1 General . 77
8.2 Transport of NAS messages over control plane . 77
8.2.1 General . 77
8.2.2 TCP packet encapsulation . 77
8.2.3 Establishment of TCP connection for transport of NAS messages . 80
8.2.3A Re-establishment of TCP connection for transport of NAS messages . 80
8.2.4 Transport of NAS messages over TCP connection . 80
8.2.5 Release of TCP connection for transport of NAS messages . 80
8.3 Transport of messages over user plane . 80
8.3.1 General . 80
8.3.2 Generic routing encapsulation (GRE) . 81
9 Parameters and coding. 83
9.1 General . 83
9.2 3GPP specific coding information . 83
9.2.1 GUAMI . 83
9.2.2 Establishment cause for non-3GPP access . 83
9.2.3 PLMN ID . 84
9.2.4 IKEv2 Notify Message Type value . 85
9.2.4.1 General . 85
9.2.4.2 Private Notify Message - Error Types . 85
9.2.4.3 Private Notify Message - Status Types . 85
9.2.5 TNGF IPv4 contact info . 86
9.2.6 TNGF IPv6 contact info . 87
9.2.7 NID . 87
9.3 IETF RFC coding information . 88
9.3.1 IKEv2 Notify payloads . 88
9.3.1.1 5G_QOS_INFO Notify payload. 88
9.3.1.2 NAS_IP4_ADDRESS Notify payload . 95
9.3.1.3 NAS_IP6_ADDRESS Notify payload . 95
9.3.1.4 UP_IP4_ADDRESS Notify payload . 96
9.3.1.5 UP_IP6_ADDRESS Notify payload . 97
9.3.1.6 NAS_TCP_PORT Notify payload . 97
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9.3.1.7 N3GPP_BACKOFF_TIMER Notify payload . 98
9.3.1.8 UP_SA_INFO Notify payload . 98
9.3.2 EAP-5G method . 99
9.3.2.1 General . 99
9.3.2.2 Message format . 99
9.3.2.2.1 EAP-Request/5G-Start message . 99
9.3.2.2.2 EAP-Response/5G-NAS message . 100
9.3.2.2.3 EAP-Request/5G-NAS message . 104
9.3.2.2.4 EAP-Response/5G-Stop message . 105
9.3.2.2.5 EAP-Request/5G-Notification message . 106
9.3.2.2.6 EAP-Response/5G-Notification message . 108
9.3.3 GRE encapsulated user data packet . 109
9.4 NAS message envelope . 110
Annex A (informative): Change history . 112
History . 118

ETSI
3GPP TS 24.502 version 19.3.0 Release 19 8 ETSI TS 124 502 V19.3.0 (2026-03)
Foreword
This Technical Specification has been produced by the 3rd Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
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