ETSI TS 129 561 V19.5.0 (2026-03)

5G; 5G System; Interworking between 5G Network and external Data Networks; Stage 3 (3GPP TS 29.561 version 19.5.0 Release 19)

RTS/TSGC-0329561vj50

General Information

• Status: Not Published
• Technical Committee: 3GPP CT 3 - Interworking with external networks (formely CN3)
• Current Stage: 8 - Draft receipt by ETSI Secretariat
• Completion Date: 10-Mar-2026

Standards Content (Sample)

TECHNICAL SPECIFICATION
5G;
5G System;
Interworking between 5G Network and external Data Networks;
Stage 3
(3GPP TS 29.561 version 19.5.0 Release 19)


3GPP TS 29.561 version 19.5.0 Release 19 1 ETSI TS 129 561 V19.5.0 (2026-03)

Reference
RTS/TSGC-0329561vj50
Keywords
5G
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ETSI
3GPP TS 29.561 version 19.5.0 Release 19 2 ETSI TS 129 561 V19.5.0 (2026-03)
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ETSI
3GPP TS 29.561 version 19.5.0 Release 19 3 ETSI TS 129 561 V19.5.0 (2026-03)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 7
1 Scope . 8
2 References . 8
3 Definitions and abbreviations . 11
3.1 Definitions . 11
3.2 Abbreviations . 11
4 Network Characteristics . 12
4.1 Key characteristics of PLMN . 12
4.2 Key characteristics of IP Networks . 12
4.3 Key characteristics of Ethernet . 12
5 Interworking Classifications. 12
5.1 Service Interworking . 12
5.2 Network Interworking . 13
6 Reference Architecture . 13
7 Interface to 5G Network services (User Plane) . 14
8 Interworking with DN (IP) . 14
8.1 General . 14
8.2 DN Interworking Model . 14
8.2.1 General . 14
8.2.2 Access to DN through 5G Network . 15
8.2.2.1 Transparent access to DN . 15
8.2.2.2 IPv4 Non-transparent access to DN . 16
8.2.2.3 IPv6 Non-transparent access to DN . 17
8.3 Transport Level Marking . 19
9 Interworking with DN (Unstructured) . 19
9.1 General . 19
9.2 N6 PtP tunnelling based on UDP/IP . 19
9.3 Other N6 tunnelling mechanism . 20
10 Interworking with DN (DHCP) . 21
10.1 General . 21
10.2 DN interworking Model of SMF or SMF+PGW-C for DHCP . 21
10.2.2 IPv4 Address allocation and IPv4 parameter configuration via DHCPv4 . 22
10.2.3 IPv6 Prefix allocation via IPv6 stateless address autoconfiguration via DHCPv6 . 23
10.2.4 IPv6 parameter configuration via stateless DHCPv6 . 24
10.2.5 IPv6 Prefix Delegation via DHCPv6 . 25
10.2.5.1 General requirement . 25
10.2.5.2 Additional requirement to support RG . 25
10.3 3GPP Vendor-Specific Options . 26
11 Interworking with DN-AAA (RADIUS) . 27
11.1 RADIUS procedures. 27
11.1.1 RADIUS Authentication and Authorization in 5GC . 27
11.1.1a RADIUS Authentication and Authorization in EPC Interworking . 28
11.1.2 RADIUS Accounting . 29
11.2 Message flows on N6 interface . 30
11.2.1 Authentication, Authorization and Accounting procedures in 5GC . 30
11.2.1a Authentication and Authorization procedures in EPC Interworking . 33
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11.2.2 Accounting Update . 36
11.2.3 DN-AAA initiated QoS flow termination . 37
11.2.4 DN-AAA initiated re-authorization in 5GC . 38
11.2.4a DN-AAA initiated re-authorization in EPC Interworking . 39
11.3 List of RADIUS attributes . 40
11.3.1 General . 40
11.3.2 Change-of-Authorization Request (optionally sent from DN-AAA server to SMF) . 56
11.3.3 Access-Challenge (sent from DN-AAA server to SMF) . 57
12 Interworking with DN-AAA (Diameter) . . 57
12.1 Diameter Procedures . 57
12.1.1 Diameter Authentication and Authorization . 57
12.1.1a Diameter Authentication and Authorization in EPC Interworking . 58
12.1.2 Diameter Accounting . 60
12.2 Message flows on N6 interface . 61
12.2.1 Authentication, Authorization and Accounting procedures . 61
12.2.1a Authentication and Authorization procedures in EPC Interworking . 64
12.2.2 Accounting Update . 66
12.2.3 DN-AAA initiated QoS flow termination . 67
12.2.4 DN-AAA initiated re-authorization in 5GC . 68
12.2.4a DN-AAA initiated re-authorization in EPC Interworking . 69
12.2.5 DN-AAA initiated re-authentication and re-authorization in 5GC . 69
12.2.5a DN-AAA initiated re-authentication and re-authorization in EPC Interworking. 70
12.2.5b DN-AAA initiated re-authentication and re-authorization for MA PDU Session. 71
12.3 N6 specific AVPs . 71
12.4 N6 re-used AVPs . 71
12.4.0 General . 71
12.4.1 Use of the Supported-Features AVP on the N6 reference point . 74
12.5 N6 specific Experimental-Result-Code AVP . 75
12.6 N6 Diameter messages . 75
12.6.1 General . 75
12.6.2 DER Command . 76
12.6.3 DEA Command . 77
12.6.4 RAR Command . 78
12.6.5 RAA Command . 79
13 Interworking with IMS . 79
13.1 General . 79
13.2 IMS interworking Model . 80
13.2.1 Introduction. 80
13.2.2 IMS specific configuration in the SMF . 80
13.2.3 IMS specific procedures in the SMF . 81
13.2.3.1 Provisioning of Signalling Server Address . 81
13.2.3.2 Failure of Signalling Server Address . 81
14 Interworking with DN (Ethernet) . 81
15 Interworking with DN (Multicast Routing Protocol) . 82
15.1 General . 82
15.2 DN interworking Model of UPF for PIM . 82
16 Interworking with NSS-AAA (RADIUS) . . 83
16.1 RADIUS procedures. 83
16.1.1 General . 83
16.1.2 RADIUS Authentication and Authorization . 83
16.2 Message flows for network slice specific authentication . 84
16.2.1 Authentication and Authorization procedures . 84
16.2.2 NSS-AAA initiated revocation of network slice authorization . 85
16.3 List of RADIUS attributes . 86
16.3.1 General . 86
17 Interworking with NSS-AAA (Diameter) . 87
17.1 Diameter procedures . 87
17.1.1 General . 87
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17.1.2 Diameter Authentication and Authorization . 87
17.2 Message flows for network slice specific authentication . 87
17.2.1 Authentication and Authorization procedures . 87
17.2.2 NSS-AAA initiated revocation of network slice authorization . 89
17.2.3 NSS-AAA initiated re-authentication and re-authorization . 90
17.3 Specific AVPs . 91
17.4 re-used AVPs . 91
17.4.1 General . 91
17.4.2 Use of the Supported-Features AVP . 91
17.5 Specific Experimental-Result-Code AVP . 92
17.6 Diameter messages . 92
17.6.1 General . 92
18 Interworking with DN (L2TP tunnel) . 93
18.1 Support L2TP for CUPS across N6 . 93
19 Interworking with Credentials Holder using AAA server . 96
19.1 Credentials Holder using AAA server for primary authentication and authorization . 96
19.2 Credentials Holder using AAA server for primary authentication procedure . 96
20 Interworking with MBS Application Provider (AF/AS) . 97
20.1 General . 97
20.2 MBS interworking user plane reference point architecture . 97
20.3 User Plane Protocol between MB-UPF and MBS AF/AS or MBSTF . 98
20.4 User Plane Protocol between MBSTF and MBS AF/AS or NEF . 99
21 Interworking with AAA server in DCS for UE onboarding in SNPNs . 100
21.0 General . 100
21.1 Primary authentication using AAA server in DCS . 100
21.2 Secondary authentication using AAA server in DCS . 100
22 Interworking with DN for e2e encrypted traffic . 101
22.1 General . 101
22.2 Media Related Information. 101
22.3 Connect-UDP . 104
22.3.1 Introduction. 104
22.3.2 Sending Media Related Information using proxying UDP in HTTP Datagram . 104
22.3.3 Sending Media Related Information using transport options for UDP . 105
22.3.4 Sending Media Related Information using QUIC-aware proxying using HTTP . 106
22.3.5 Sending Media Related Information using Media over QUIC transport . 108
Annex A (normative): Rate control related to 5G Cellular Internet of Things (CIoT) optimisations . 109
A.1 General . 109
A.2 Support of rate control of user data . 109
A.2.1 General . 109
A.2.2 Small Data Rate Control . 109
A.2.3 Serving PLMN Rate Control information handling . 110
A.3: TS29561_CustomHeaders ABNF . 110
A.3.1 General . 110
A.3.2 ABNF definitions (Filename:"TS29561_CustomHeaders.abnf") . 111
Annex B (informative): IANA registration of 3GPP defined Forwarded Mode packets . 113
B.1 Introduction . 113
B.2 3GPP_MRI_AESCCM_8 . 113
B.3 Full Nonce Counter Capsule . 113
B.4 TLS Exporter Label . 114
Annex C (informative): IANA registration of 3GPP defined UDP Options Kind number . 114
C.1 Introduction . 114
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C.2 UDP Options Kind Number . 114
Annex D (informative): IANA registration of 3GPP defined MoQ Extension headers . 116
Annex E (informative): Change history . 117
History . 120

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Foreword
rd
This Technical Specification has been produced by the 3 Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
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3GPP TS 29.561 version 19.5.0 Release 19 8 ETSI TS 129 561 V19.5.0 (2026-03)
1 Scope
The present specification defines the stage 3 interworking procedures for 5G Network interworking between PLMN and
external DN or Network Slice Specific AAA.
The stage 2 requirements and procedures are contained in 3GPP TS 23.501 [2] and 3GPP TS 23.502 [3].
For interworking between 5G PLMN and external DNs, the present document is valid for both 3GPP accesses and non-
3GPP accesses.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
- References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
- For a specific reference, subsequent revisions do not apply.
- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TS 23.501: "System Architecture for the 5G System; Stage 2".
[3] 3GPP TS 23.502: "Procedures for the 5G System; Stage 2".
[4] 3GPP TS 29.281: "General Packet Radio System (GPRS) Tunnelling Protocol User Plane
(GTPv1-U)".
[5] 3GPP TS 29.061: "Interworking between the Public Land Mobile Network (PLMN) supporting
packet based services and Packet Data Networks (PDN)".
[6] IETF RFC 3748: "Extensible Authentication Protocol (EAP)".
[7] IETF RFC 3579: "RADIUS (Remote Authentication Dial In User Service) Support For Extensible
Authentication Protocol (EAP)".
[8] IETF RFC 2865: "Remote Authentication Dial In User Service (RADIUS)".
[9] IETF RFC 3162: "RADIUS and IPv6".
[10] IETF RFC 4818: "RADIUS Delegated-IPv6-Prefix Attribute".
[11] IETF RFC 5216: "The EAP-TLS Authentication Protocol".
[12] 3GPP TS 23.228: "IP Multimedia Subsystem (IMS); Stage 2".
[13] 3GPP TS 24.229: "IP Multimedia Call Control Protocol based on SIP and SDP; Stage 3".
[14] IETF RFC 2132: "DHCP Options and BOOTP Vendor Extensions".
[15] IETF RFC 3361: "Dynamic Host Configuration Protocol (DHCP-for-IPv4) Option for Session
Initiation Protocol (SIP) Servers".
[16] IETF RFC 3646: "DNS Configuration options for Dynamic Host Configuration Protocol for IPv6
(DHCPv6)".
[17] IETF RFC 3319: "Dynamic Host Configuration Protocol (DHCPv6) Options for Session Initiation
Protocol (SIP) Servers".
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[18] IETF RFC 2131: "Dynamic Host Configuration Protocol".
[19] IETF RFC 1542: "Clarification and Extensions for the Bootstrap Protocol".
[20] IETF RFC 4039: "Rapid Commit Option for the Dynamic Host Configuration Protocol version 4
(DHCPv4)".
[21] IETF RFC 8415: "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)".
[22] Void
[23] IETF RFC 7155: "Diameter Network Access Server Application".
[24] IETF RFC 6733: "Diameter Base Protocol".
[25] IETF RFC 4072: "Diameter Extensible Authentication Protocol (EAP) Application".
[26] IETF RFC 2866: "RADIUS Accounting".
[27] IETF RFC 5176: "Dynamic Authorization Extensions to Remote Authentication Dial In User
Service (RADIUS)".
[28] 3GPP TS 23.003: "Numbering, addressing and identification".
[29] IETF RFC 1825: "Security Architecture for the Internet Protocol".
[30] IETF RFC 1826: "IP Authentication Header".
[31] IETF RFC 1827: "IP Encapsulating Security Payload (ESP)".
[32] IETF RFC 4291: "IP Version 6 Addressing Architecture".
[33] IETF RFC 4861: "Neighbor Discovery for IP Version 6 (IPv6)".
[34] IETF RFC 4862: "IPv6 Stateless Address Autoconfiguration".
[35] IETF RFC 1027: "Using ARP to Implement Transparent Subnet Gateways".
[36] 802.3-2015 - IEEE Standard for Ethernet.
[37] IETF RFC 5281: "Extensible Authentication Protocol Tunneled Transport Layer Security
Authenticated Protocol Version 0 (EAP-TTLSv0)".
[38] 3GPP TS 23.380: "IMS Restoration Procedures".
[39] 3GPP TS 29.571: "5G System; Common Data Types for Service Based Interfaces; Stage 3".
[40] 3GPP TS 29.502: "5G System; Session Management Services; Stage 3".
[41] 3GPP TS 29.229: "Cx and Dx interfaces based on Diameter protocol; Protocol details".
[42] 3GPP TS 24.501: "Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3".
[43] 3GPP TS 23.316: "Wireless and wireline convergence access support for the 5G System (5GS)".
[44] IETF RFC 7761: "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol
Specification (Revised)".
[45] IETF RFC 3973: "Protocol Independent Multicast - Dense Mode (PIM-DM): Protocol
Specification (Revised)".
[46] 3GPP TS 29.571: "5G System; Common Data Types for Service Based Interfaces Stage 3".
[47] IETF RFC 2132: "DHCP Options and BOOTP Vendor Extensions".
[48] IETF RFC 3925: "Vendor-Identifying Vendor Options for Dynamic Host Configuration Protocol
version 4 (DHCPv4)".
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[49] IETF RFC 8415: "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)".
[50] 3GPP TS 29.274: "3GPP Evolved Packet System. Evolved GPRS Tunnelling Protocol for EPS
(GTPv2)".
[51] CableLabs WR-TR-5WWC-ARCH: "5G Wireless Wireline Converged Core Architecture".
[52] BBF WT-470: "5G FMC Architecture".
[53] 3GPP TS 23.401: "General Packet Radio Service (GPRS) enhancements for Evolved Universal
Terrestrial Radio Access Network (E-UTRAN) access".
[54] BBF TR-456: "AGF Functional Requirements".
[55] CableLabs DOCSIS MULPI: "Data-Over-Cable Service Interface Specifications DOCSIS 3.1,
MAC and Upper Layer Protocols Interface Specification".
[56] IETF RFC 7542: "The Network Access Identifier".
[57] IETF RFC 2661: " Layer Two Tunneling Protocol "L2TP".
[58] 3GPP TS 29.244: "Interface between the Control Plane and the User Plane of EPC Nodes;
Stage 3".
[59] 3GPP TS 33.501: "Security architecture and procedures for 5G system".
[60] 3GPP TS 23.247: "Architectural enhancements for 5G multicast-broadcast services; Stage 2".
[61] 3GPP TS 26.502: "5G Multicast-Broadcast User Service Architecture".
[62] IETF RFC 6603: "Prefix Exclude Option for DHCPv6-based Prefix Delegation".
[63] 3GPP TS 23.434: "Service Enabler Architecture Layer for Verticals (SEAL); Functional
architecture and information flows".
[64] IETF RFC 9298: "Proxying UDP in HTTP"
[65] IETF RFC 9114: "Hypertext Transfer Protocol Version 3 (HTTP/3)"
[66] IETF RFC 9868: "Transport Options for UDP".
[67] draft-ietf-masque-quic-proxy: "QUIC-Aware Proxying Using HTTP".
Editor's note: The above reference will be revised to RFC when finalized by IETF.
[68] IETF RFC 9000: "QUIC: A UDP-Based Multiplexed and Secure Transport"
[69] draft-ietf-moq-transport: "Media over QUIC Transport".
Editor's note: The above reference will be revised to RFC when finalized by IETF.
[70] 3GPP TS 26.522: "5G Real-time Media Transport Protocol Configurations".
[71] IEEE 802.1Q-2022: "IEEE Standard for Local and metropolitan area networks--Bridges and
Bridged Networks".
[72] IETF RFC 9297: "HTTP Datagrams and the Capsule Protocol"
[73] IETF RFC 5705: "Keying Material Exporters for Transport Layer Security (TLS)"
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3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in 3GPP TR 21.905 [1] and the following
apply. A term defined in the present document takes precedence over the definition of the same term, if any, in
3GPP TR 21.905 [1].
MA PDU Session: A PDU Session that provides a PDU connectivity service, which can use one access network at a
time, or simultaneously one 3GPP access network and one non-3GPP access network.
3.2 Abbreviations
For the purposes of the present document, the abbreviations given in 3GPP TR 21.905 [1] and the following apply. An
abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in
3GPP TR 21.905 [1].
5G-BRG 5G Broadband Residential Gateway
5G-CRG 5G Cable Residential Gateway
AMF Access and Mobility Management Function
AS Application Server
BBF Broadband Forum
CH Credentials Holder
CHAP Challenge Handshake Authentication Protocol
CHF Charging Function
CSMA/CD Carrier Sense Multiple Access/Collision Detection
DCS Default Credentials Server
DHCPv4 Dynamic Host Configuration Protocol version 4
DHCPv6 Dynamic Host Configuration Protocol version 6
DN Data Network
DNAI DN Access Identifier
DR Designated Router
DSL Digital Subscriber Line
FN-BRG Fixed Network Broadband RG
FN-CRG Fixed Network Cable RG
FQDN Fully Qualified Domain Name
GCI Global Cable Identifier
GLI Global Line Identifier
GPSI Generic Public Subscription Identifier
HFC Hybrid Fiber Coax
I-SMF Intermediate SMF
L2TP Layer Two Tunneling Protocol
LAC L2TP Access Concentrator
LNS L2TP Network Server
MBS Multicast/Broadcast Service.
MBSTF Multicast/Broadcast Service Transport Function.
MB-UPF Multicast/Broadcast User Plane Function
MRI Media Related Information
MSK Master Session Key
N3IWF Non-3GPP InterWorking Function
NGAP NG Application Protocol
NRM Network Resource Management
NSS Network Slice Specific
NSSAAF Network Slice-Specific Authentication and Authorization Function
ON-SNPN Onboarding Standalone Non-Public Network
PAP Password Authentication Protocol
P-GW PDN Gateway
PGW-C PDN Gateway Control plane function
PGW-U PDN Gateway User plane function
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PIM Protocol-Independent Multicast
PIM-DM Protocol-Independent Multicast- Dense Mode
PIM-SM Protocol-Independent Multicast- Sparse Mode
PON Passive Optical Network
PtP Point-to-Point
RG Residential Gateway
RP Rendezvous Point
RSN Redundancy Sequence Number
RTP Real-time Transport Protocol
SD Slice Differentiator
SEAL Service Enabler Architecture Layer for Verticals
SFD Start Frame Delimiter
SMF Session Management Function
S-NSSAI Single Network Slice Selection Assistance Information
SNPN Stand-alone Non-Public Network
SO-SNPN Subscription Owner Standalone Non-Public Network
SSC Session and Service Continuity
SST Slice/Service Type
TCP Transmission Control Protocol
TNAP Trusted Non-3GPP Access Point
TWAP Trusted WLAN Access Point
UDP User Datagram Protocol
UPF User Plane Function
V-SMF Visited SMF
VAL Vertical Application Layer
WAN Wide Area Network
4 Network Characteristics
4.1 Key characteristics of PLMN
The PLMN is fully defined in the 3GPP technical specifications. The 5G Network related key characteristics are
defined in 3GPP TS 23.501 [2].
4.2 Key characteristics of IP Networks
The Internet is a conglomeration of networks utilising a common set of protocols. IP protocols are defined in the
relevant IETF RFCs. The networks topologies may be based on LANs (e.g. Ethernet), Point to Point leased lines,
PSTN, ISDN, X.25 or WANs using switched technology (e.g. SMDS, ATM).
4.3 Key characteristics of Ethernet
The Ethernet is a family of computer networking technologies commonly used in LAN and is often used to refer to all
Carrier Sense Multiple Access/Collision Detection (CSMA/CD) LANs that generally conform to Ethernet
Specifications, including IEEE 802.3 [36]. The key characteristics for Ethernet are defined in IEEE 802.3 [36].
5 Interworking Classifications
5.1 Service Interworking
Service interworking is required when the Teleservice at the calling and called terminals are different. No service
interworking is specified in this specification.
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5.2 Network Interworking
Network interworking is required whenever a PLMN is involved in communications with another network to provide
end-to-end communications. The PLMN shall interconnect in a manner consistent with that of a normal Data Network
(type defined by the requirements e.g. IP). Interworking appears exactly like that of Data Networks.
6 Reference Architecture
Figure 6-1 shows the access interfaces for the 5G Network. Figure 6-2 sho
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