ETSI TS 129 500 V17.16.0 (2026-02)

5G; 5G System; Technical Realization of Service Based Architecture; Stage 3 (3GPP TS 29.500 version 17.16.0 Release 17)

RTS/TSGC-0429500vhg0

General Information

• Status: Not Published
• Technical Committee: 3GPP CT 4 - MAP/CAMEL/GTP/BCH/SS/TrFO/IMS/GUP/WLAN (formely CN4)
• Current Stage: 12 - Citation in the OJ (auto-insert)
• Completion Date: 04-Feb-2026

Standards Content (Sample)

TECHNICAL SPECIFICATION
5G;
5G System;
Technical Realization of Service Based Architecture;
Stage 3
(3GPP TS 29.500 version 17.16.0 Release 17)

3GPP TS 29.500 version 17.16.0 Release 17 1 ETSI TS 129 500 V17.16.0 (2026-02)

Reference
RTS/TSGC-0429500vhg0
Keywords
5G
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ETSI
3GPP TS 29.500 version 17.16.0 Release 17 2 ETSI TS 129 500 V17.16.0 (2026-02)
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ETSI
3GPP TS 29.500 version 17.16.0 Release 17 3 ETSI TS 129 500 V17.16.0 (2026-02)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 8
1 Scope . 10
2 References . 10
3 Definitions and abbreviations . 12
3.1 Definitions . 12
3.2 Abbreviations . 13
3.3 Special characters, operators and delimiters . 13
3.3.1 General . 13
3.3.2 ABNF operators . 13
3.3.3 URI – reserved and special characters . 13
3.3.4 SBI specific usage of delimiters . 13
4 Service Based Architecture Overview. 14
4.1 NF Services . 14
4.2 Service Based Interfaces . 14
4.3 NF Service Framework . 14
4.3.1 General . 14
4.3.2 NF Service Advertisement URI . 14
5 Protocols Over Service Based Interfaces . 15
5.1 Protocol Stack Overview . 15
5.2 HTTP/2 Protocol . 15
5.2.1 General . 15
5.2.2 HTTP standard headers . 15
5.2.2.1 General . 15
5.2.2.2 Mandatory to support HTTP standard headers . 16
5.2.3 HTTP custom headers . 18
5.2.3.1 General . 18
5.2.3.2 Mandatory to support custom headers. 19
5.2.3.2.1 General . 19
5.2.3.2.2 3gpp-Sbi-Message-Priority . 24
5.2.3.2.3 3gpp-Sbi-Callback . 24
5.2.3.2.4 3gpp-Sbi-Target-apiRoot . 24
5.2.3.2.5 3gpp-Sbi-Routing-Binding . 25
5.2.3.2.6 3gpp-Sbi-Binding . 26
5.2.3.2.7 3gpp-Sbi-Discovery . 29
5.2.3.2.8 3gpp-Sbi-Producer-Id . 30
5.2.3.2.9 3gpp-Sbi-Oci . 31
5.2.3.2.10 3gpp-Sbi-Lci . 33
5.2.3.2.11 3gpp-Sbi-Client-Credentials . 35
5.2.3.2.12 3gpp-Sbi-Nrf-Uri . 36
5.2.3.2.13 3gpp-Sbi-Target-Nf-Id . 37
5.2.3.2.14 3gpp-Sbi-Max-Forward-Hops . 37
5.2.3.2.16 3gpp-Sbi-Access-Scope . 38
5.2.3.2.17 3gpp-Sbi-Access-Token . 38
5.2.3.2.18 Void . 39
5.2.3.2.19 3gpp-Sbi-Target-Nf-Group-Id . 39
5.2.3.2.20 3gpp-Sbi-Nrf-Uri-Callback . 39
5.2.3.2.21 3gpp-Sbi-NF-Peer-Info . 39
5.2.3.2.22 3gpp-Sbi-Source-NF-Client-Credentials . 40
5.2.3.3 Optional to support custom headers . 40
5.2.3.3.1 General . 40
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5.2.3.3.2 3gpp-Sbi-Sender-Timestamp . 43
5.2.3.3.3 3gpp-Sbi-Max-Rsp-Time. 43
5.2.3.3.4 3gpp-Sbi-Correlation-Info . 43
5.2.3.3.5 3gpp-Sbi-Alternate-Chf-Id . 44
5.2.3.3.6 3gpp-Sbi-Notif-Accepted-Encoding . 45
5.2.3.3.7 3gpp-Sbi-Consumer-Info . 45
5.2.3.3.8 3gpp-Sbi-Response-Info . 46
5.2.3.3.9 Void . 47
5.2.3.3.10 3gpp-Sbi-Selection-Info . 47
5.2.3.3.11 3gpp-Sbi-Interplmn-Purpose . 48
5.2.3.3.12 3gpp-Sbi-Request-Info . 49
5.2.4 HTTP error handling . 50
5.2.5 HTTP/2 server push . 50
5.2.6 HTTP/2 connection management . 50
5.2.7 HTTP status codes . 51
5.2.7.1 General . 51
5.2.7.2 NF as HTTP Server . 52
5.2.7.3 NF as HTTP Client . 57
5.2.7.4 SCP/SEPP . 58
5.2.8 HTTP/2 request retries . 61
5.2.9 Handling of unsupported query parameters . 62
5.2.10 URL Encoding of data . 62
5.2.10.1 General . 62
5.2.10.2 URL Encoding of URI components . 63
5.2.10.3 URL Encoding of HTTP/2 request bodies . 64
5.3 Transport Protocol . 64
5.4 Serialization Protocol . 64
5.5 Interface Definition Language . 65
6 General Functionalities in Service Based Architecture . 65
6.1 Routing Mechanisms . 65
6.1.1 General . 65
6.1.2 Identifying a target resource . 65
6.1.3 Connecting inbound . 65
6.1.4 Pseudo-header setting . 65
6.1.4.1 General . 65
6.1.4.2 Routing within a PLMN . 66
6.1.4.3 Routing across PLMN . 66
6.1.4.3.1 General . 66
6.1.4.3.2 Use of telescopic FQDN between NFs and SEPP within a PLMN . 67
6.1.4.3.3 Use of 3gpp-Sbi-Target-apiRoot between NFs and SEPP within a PLMN . 67
6.1.4.3.4 Routing between SEPPs . 68
6.1.5 Host header . 68
6.1.6 Message forwarding . 68
6.2 Server-Initiated Communication . 68
6.2.1 General . 68
6.2.2 Subscription on behalf of NF Service Consumer . 69
6.3 Load Control . 70
6.3.1 General . 70
6.3.2 Load Control based on load signalled via the NRF . 70
6.3.3 Load Control based on LCI Header . 70
6.3.3.1 General . 70
6.3.3.2 Conveyance of Load Control Information . 71
6.3.3.3 Frequency of Conveyance . 71
6.3.3.4 Load Control Information . 71
6.3.3.4.1 General Description . 71
6.3.3.4.2 Load Control Timestamp . 72
6.3.3.4.3 Load Metric . 72
6.3.3.4.4 Scope of LCI . 72
6.3.3.4.5 S-NSSAI/DNN Relative Capacity . 74
6.3.3.5 LC-H feature support . 75
6.3.3.5.1 Indicating supports for the LC-H feature . 75
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6.3.3.5.2 Utilizing the LC-H feature support indication . 75
6.4 Overload Control . 75
6.4.1 General . 75
6.4.2 Overload Control based on HTTP status codes . 76
6.4.2.1 General . 76
6.4.2.2 HTTP Status Code "503 Service Unavailable" . 76
6.4.2.3 HTTP Status Code "429 Too Many Requests" . 77
6.4.2.4 HTTP Status Code "307 Temporary Redirect" . 77
6.4.3 Overload Control based on OCI Header . 77
6.4.3.1 General . 77
6.4.3.2 Conveyance of Overload Control Information . 78
6.4.3.3 Frequency of Conveyance . 78
6.4.3.4 Overload Control Information . 78
6.4.3.4.1 General Description . 78
6.4.3.4.2 Overload Control Timestamp . 79
6.4.3.4.3 Overload Reduction Metric . 80
6.4.3.4.4 Overload Control Period of Validity . 80
6.4.3.4.5 Scope of OCI . 80
6.4.3.5 Overload Control Enforcement . 84
6.4.3.5.1 Message Throttling . 84
6.4.3.5.2 Loss Algorithm . 85
6.4.3.6 OLC-H feature support . 85
6.4.3.6.1 Indicating supports for the OLC-H feature . 85
6.5 Support of Stateless NFs . 85
6.5.1 General . 85
6.5.2 Stateless AMFs . 85
6.5.2.1 General . 85
6.5.2.2 AMF as service consumer . 85
6.5.2.3 AMF as service producer . 86
6.5.3 Stateless NFs (for any 5GC NF type) . 87
6.5.3.1 General . 87
6.5.3.2 Stateless NF as service consumer . 87
6.5.3.3 Stateless NF as service producer . 88
6.6 Extensibility Mechanisms . 89
6.6.1 General . 89
6.6.2 Feature negotiation . 89
6.6.3 Vendor-specific extensions . 91
6.6.4 Extensibility for Query parameters . 91
6.7 Security Mechanisms . 92
6.7.1 General . 92
6.7.2 Transport layer security protection of messages . 92
6.7.3 Authorization of NF service access . 92
6.7.4 Application layer security across PLMN . 93
6.7.4.1 General . 93
6.7.4.2 N32 Procedures . 94
6.7.5 Client credentials assertion and authentication . 94
6.7.5.1 General . 94
6.7.5.2 Authorization of NF Service Consumers for data access via DCCF . 94
6.8 SBI Message Priority Mechanism . 95
6.8.1 General . 95
6.8.2 Message level priority . 95
6.8.3 Stream priority . 96
6.8.4 Recommendations when defining SBI Message Priorities . 96
6.8.5 HTTP/2 client behaviour . 97
6.8.6 HTTP/2 server behaviour . 97
6.8.7 HTTP/2 proxy behaviour . 97
6.8.8 DSCP marking of messages . 98
6.9 Discovering the supported communication options . 98
6.9.1 General . 98
6.9.2 Discoverable communication options . 98
6.9.2.1 Content-encodings supported in HTTP requests . 98
6.9.2.2 Content-encodings supported in HTTP responses . 99
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6.10 Support of Indirect Communication . 99
6.10.1 General . 99
6.10.2 Routing Mechanisms with SCP Known to the NF . 99
6.10.2.1 General . 99
6.10.2.2 HTTP/2 connection management . 100
6.10.2.3 Connecting inbound . 100
6.10.2.4 Pseudo-header setting. 100
6.10.2.5 3gpp-Sbi-Target-apiRoot header setting . 101
6.10.2.6 Cache key (ck) query parameter . 102
6.10.2A Routing Mechanism with SCP Unknown to the NF . 102
6.10.2A.1 Connecting inbound . 102
6.10.2A.2 HTTP/2 connection management . 102
6.10.2A.3 Pseudo-header setting. 103
6.10.3 NF Discovery and Selection for indirect communication with Delegated Discovery . 103
6.10.3.1 General . 103
6.10.3.2 Conveyance of NF Discovery Factors. 103
6.10.3.3 Notifications corresponding to default notification subscriptions . 104
6.10.3.4 Returning the Producer's NF Instance ID and NF Group ID to the NF Service Consumer . 105
6.10.3.5 Returning an Alternate CHF instance ID to the NF Service Consumer . 105
6.10.4 Authority and/or deployment-specific string in apiRoot of resource URI . 106
6.10.5 NF / NF service instance selection for Indirect Communication without Delegated Discovery . 107
6.10.5.1 General . 107
6.10.5.2 Notifications corresponding to default notification subscriptions . 108
6.10.6 Feature negotiation for Indirect Communication with Delegated Discovery . 109
6.10.7 Notification and callback requests sent with Indirect Communication . 109
6.10.8 Error Handling . 109
6.10.8.1 General . 109
6.10.8.2 Requirements for the originator of an HTTP error response . 110
6.10.8.3 Requirements for an SCP or SEPP relaying an HTTP error response . 111
6.10.9 HTTP redirection . 111
6.10.9.1 General . 111
6.10.10 Detection and handling of loop path when relaying message with indirect communication . 112
6.10.10.1 General . 112
6.10.10.2 Message Forwarding Depth Control . 112
6.10.10.3 Loop Detection with Via header . 112
6.10.11 Authorization of NF service access . 113
6.10.11.1 General . 113
6.10.11.2 Authorization for indirect communication with delegated discovery . 113
6.10.11.2.1 General . 113
6.10.11.2.2 Error handling when the SCP fails to obtain an access token . 114
6.10.11.2.3 Error handling when SCP receives a "401 Unauthorized" response or a "403 Forbidden"
response with a "WWW-Authenticate" header. 114
6.10.11.3 Authorization for indirect communication without delegated discovery . 115
6.11 Detection and handling of late arriving requests . 115
6.11.1 General . 115
6.11.2 Detection and handling of requests which have timed out at the HTTP client . 115
6.11.2.1 General . 115
6.11.2.2 Principles . 115
6.12 Binding between an NF Service Consumer and an NF Service Resource. 116
6.12.1 General . 116
6.12.2 Binding created as part of a service response . 118
6.12.3 Binding created as part of a service request . 119
6.12.4 Binding for explicit or implicit subscription requests . 119
6.12.5 Binding for service requests creating a callback resource . 121
6.13 SBI messages correlation for network troubleshooting . 121
6.13.1 General . 121
6.13.2 SBI messages correlation using UE identifier . 122
6.13.2.1 General . 122
6.13.2.2 Principles . 122
6.13.3 SBI messages correlation using NF Peer Information . 122
6.13.3.1 General . 122
6.13.3.2 Principles . 123
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6.14 Indicating the purpose of Inter-PLMN signaling. 123
6.14.1 General . 123
6.14.2 Inclusion of the intended purpose . 123
6.14.3 Evaluating the intended purpose . 123
Annex A (informative): Client-side Adaptive Throttling for Overload Control . 125
Annex B (normative): 3gpp-Sbi-Callback Types . 126
Annex C (informative): Internal NF Routing of HTTP Requests . 127
Annex D (informative): Change history . 128
History . 134

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