ETSI TS 129 573 V15.3.1 (2019-11)

TECHNICAL SPECIFICATION
5G;
5G System;
Public Land Mobile Network (PLMN) Interconnection;
Stage 3
(3GPP TS 29.573 version 15.3.1 Release 15)


3GPP TS 29.573 version 15.3.1 Release 15 1 ETSI TS 129 573 V15.3.1 (2019-11)

Reference
RTS/TSGC-0429573vf31
Keywords
5G
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3GPP TS 29.573 version 15.3.1 Release 15 2 ETSI TS 129 573 V15.3.1 (2019-11)
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3GPP TS 29.573 version 15.3.1 Release 15 3 ETSI TS 129 573 V15.3.1 (2019-11)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 6
1 Scope . 7
2 References . 7
3 Definitions and abbreviations . 8
3.1 Definitions . 8
3.2 Abbreviations . 8
4 General Description . 8
4.1 Introduction . 8
4.2 N32 Interface . 8
4.2.1 General . 8
4.2.2 N32-c Interface . 9
4.2.3 N32-f Interface . 9
4.3 Protocol Stack . 10
4.3.1 General . 10
4.3.2 HTTP/2 Protocol . 10
4.3.2.1 General . 10
4.3.2.2 HTTP standard headers . 10
4.3.2.3 HTTP custom headers . 11
4.3.2.4 HTTP/2 connection management . 11
4.3.3 Transport Protocol . 11
4.3.4 Serialization Protocol . 11
5 N32 Procedures . 12
5.1 Introduction . 12
5.2 N32 Handshake Procedures (N32-c) . 12
5.2.1 General . 12
5.2.2 Security Capability Negotiation Procedure . 12
5.2.3 Parameter Exchange Procedure . 13
5.2.3.1 General . 13
5.2.3.2 Parameter Exchange Procedure for Cipher Suite Negotiation . 13
5.2.3.3 Parameter Exchange Procedure for Protection Policy Exchange . 14
5.2.4 N32-f Context Termination Procedure . 16
5.2.5 N32-f Error Reporting Procedure . 16
5.3 JOSE Protected Message Forwarding Procedure on N32 (N32-f) . 17
5.3.1 Introduction. 17
5.3.2 Use of Application Layer Security. 17
5.3.2.1 General . 17
5.3.2.2 Protection Policy Lookup . 18
5.3.2.3 Message Reformatting . 18
5.3.2.4 Message Forwarding to Peer SEPP . 20
5.3.3 Message Forwarding to Peer SEPP when TLS is used . 21
6 API Definitions . 21
6.1 N32 Handshake API . 21
6.1.1 API URI . 21
6.1.2 Usage of HTTP . 21
6.1.2.1 General . 21
6.1.2.2 HTTP standard headers . 21
6.1.2.2.1 General . 21
6.1.2.2.2 Content type . 21
6.1.2.3 HTTP custom headers . 22
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6.1.2.3.1 General . 22
6.1.3 Resources . 22
6.1.3.1 Overview . 22
6.1.4 Custom Operations without Associated Resources . 22
6.1.4.1 Overview . 22
6.1.4.2 Operation: Security Capability Negotiation . 22
6.1.4.2.1 Description . 22
6.1.4.2.2 Operation Definition . 22
6.1.4.3 Operation: Parameter Exchange . 23
6.1.4.3.1 Description . 23
6.1.4.3.2 Operation Definition . 23
6.1.4.4 Operation: N32-f Context Terminate . 24
6.1.4.4.1 Description . 24
6.1.4.4.2 Operation Definition . 24
6.1.4.5 Operation: N32-f Error Reporting . 24
6.1.4.5.1 Description . 24
6.1.4.5.2 Operation Definition . 24
6.1.5 Data Model . 25
6.1.5.1 General . 25
6.1.5.2 Structured data types . 26
6.1.5.2.1 Introduction . 26
6.1.5.2.2 Type: SecNegotiateReqData . 26
6.1.5.2.3 Type: SecNegotiateRspData . 26
6.1.5.2.4 Type: SecParamExchReqData . 27
6.1.5.2.5 Type: SecParamExchRspData . 27
6.1.5.2.6 Type: ProtectionPolicy . 28
6.1.5.2.7 Type: ApiIeMapping . 28
6.1.5.2.8 Type: IeInfo . 29
6.1.5.2.9 Type: ApiSignature . 30
6.1.5.2.10 Type: N32fContextInfo . 30
6.1.5.2.11 Type: N32fErrorInfo . 30
6.1.5.2.12 Type: FailedModificationInfo . 30
6.1.5.2.13 Type: N32fErrorDetail . 31
6.1.5.2.14 Type: CallbackName . 31
6.1.5.3 Simple data types and enumerations . 31
6.1.5.3.1 Introduction . 31
6.1.5.3.2 Simple data types . 31
6.1.5.3.3 Enumeration: SecurityCapability. 31
6.1.5.3.4 Enumeration: HttpMethod . 32
6.1.5.3.5 Enumeration: IeType . 32
6.1.5.3.6 Enumeration: IeLocation . 32
6.1.5.3.7 Enumeration: N32fErrorType . 32
6.1.5.3.8 Enumeration: FailureReason . 33
6.1.5.4 Binary data . 33
6.1.6 Error Handling . 33
6.1.6.1 General . 33
6.1.6.2 Protocol Errors . 33
6.1.6.3 Application Errors . 33
6.2 JOSE Protected Message Forwarding API on N32 . 33
6.2.1 API URI . 33
6.2.2 Usage of HTTP . 33
6.2.2.1 General . 33
6.2.2.2 HTTP standard headers . 34
6.2.2.2.1 General . 34
6.2.2.2.2 Content type . 34
6.2.2.3 HTTP custom headers . 34
6.2.2.3.1 General . 34
6.2.3 Resources . 34
6.2.3.1 Overview . 34
6.2.4 Custom Operations without Associated Resources . 34
6.2.4.1 Overview . 34
6.2.4.2 Operation: JOSE Protected Forwarding . 34
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6.2.4.2.1 Description . 34
6.2.4.2.2 Operation Definition . 35
6.2.5 Data Model . 35
6.2.5.1 General . 35
6.2.5.2 Structured data types . 36
6.2.5.2.1 Introduction . 36
6.2.5.2.2 Type: N32fReformattedReqMsg . 36
6.2.5.2.3 Type: N32fReformattedRspMsg . 37
6.2.5.2.4 Type: DataToIntegrityProtectAndCipherBlock . 37
6.2.5.2.5 Type: DataToIntegrityProtectBlock . 38
6.2.5.2.6 Type: RequestLine . 38
6.2.5.2.7 Type: HttpHeader . 39
6.2.5.2.8 Type: HttpPayload . 40
6.2.5.2.9 Type: MetaData . 43
6.2.5.2.10 Type: Modifications . 43
6.2.5.2.11 Type: FlatJweJson . 44
6.2.5.2.12 Type: FlatJwsJson . 45
6.2.5.2.13 Type: IndexToEncryptedValue . 45
6.2.5.2.14 Type: EncodedHttpHeaderValue . 45
6.2.5.3 Simple data types and enumerations . 45
6.2.5.3.1 Introduction . 45
6.2.5.3.2 Simple data types . 45
6.2.5.3.3 Void . 46
6.2.5.3.4 Void . 46
6.2.6 Error Handling . 46
6.2.6.1 General . 46
6.2.6.2 Protocol Errors . 46
6.2.6.3 Application Errors . 46
Annex A (normative): OpenAPI Specification . 47
A.1 General . 47
A.2 N32 Handshake API . 47
A.3 JOSE Protected Message Forwarding API on N32-f. 52
Annex B (informative): Examples of N32-f Encoding . 56
B.1 General . 56
B.2 Input Message Containing No Binary Part . 56
B.3 Input Message Containing Multipart Binary Part . 57
Annex C (informative): End to end call flows when SEPP is on path . 59
C.1 General . 59
C.2 TLS security between SEPPs . 59
C.2.1 When http URI scheme is used . 59
C.2.2 When https URI scheme is used . 61
C.3 Application Layer Security between SEPPs . 64
C.3.1 When http URI scheme is used . 64
C.3.2 When https URI scheme is used . 66
Annex D (informative): Withdrawn API versions . 71
D.1 General . 71
D.2 N32 Handshake API . 71
Annex E (informative): Change history . 72
History . 73

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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
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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1 Scope
The present document specifies the stage 3 protocol and data model for the PLMN interconnection Interface. It provides
stage 3 protocol definitions and message flows, and specifies the APIs for the procedures on the PLMN interconnection
interface (i.e N32).
The 5G System stage 2 architecture and procedures are specified in 3GPP TS 23.501 [2] and 3GPP TS 23.502 [3].
The Technical Realization of the Service Based Architecture and the Principles and Guidelines for Services Definition
are specified in 3GPP TS 29.500 [4] and 3GPP TS 29.501 [5].
The stage 2 level N32 procedures are specified in 3GPP TS 33.501 [6].
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 29.500: "5G System; Technical Realization of Service Based Architecture; Stage 3".
[5] 3GPP TS 29.501: "5G System; Principles and Guidelines for Services Definition; Stage 3".
[6] 3GPP TS 33.501: "Security architecture and procedures for 5G system".
[7] IETF RFC 7540: "Hypertext Transfer Protocol Version 2 (HTTP/2)".
[8] IETF RFC 8259: "The JavaScript Object Notation (JSON) Data Interchange Format".
[9] IETF RFC 7231: "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content".
[10] IETF RFC 7230: "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing".
[11] IETF RFC 793: "Transmission Control Protocol".
[12] 3GPP TS 29.571: "5G System; Common Data Types for Service Based Interfaces Stage 3".
[13] IETF RFC 7518: "JSON Web Algorithms (JWA)".
[14] IETF RFC 7516: "JSON Web Encryption (JWE)".
[15] IETF RFC 4648: "The Base16, Base32, and Base64 Data Encodings".
[16] IETF RFC 7515: "JSON Web Signature (JWS)".
[17] IETF RFC 6901: "JavaScript Object Notation (JSON) Pointer".
[18] 3GPP TS 29.510: "Network Function Repository Services; Stage 3".
[19] 3GPP TS 23.003: "Numbering, addressing and identification".
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[20] 3GPP TR 21.900: "Technical Specification Group working methods".
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].
c-SEPP: The SEPP that is present on the NF service consumer side is called the c-SEPP.
p-SEPP: The SEPP that is present on the NF service producer side is called the p-SEPP.
NOTE: For the purpose of N32-c procedures, the two interacting SEPPs are called "initiating" SEPP and
"responding" SEPP. The c-SEPP and p-SEPP terminology is not used in this specification though it is
used in 3GPP TS 33.501 [6].
c-IPX: The IPX on the NF service consumer side.
p-IPX: The IPX of the NF service producer side.
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].
IPX IP Exchange Service
JOSE Javascript Object Signing and Encryption
JWE JSON Web Encryption
JWS JSON Web Signature
PRINS PRotocol for N32 INterconnect Security
SEPP Security and Edge Protection Proxy
TLS Transport Layer Security
4 General Description
4.1 Introduction
This clause provides a general description of the interconnect interfaces used between the PLMNs for transporting the
service based interface message exchanges.
4.2 N32 Interface
4.2.1 General
The N32 interface is used between the SEPPs of a VPLMN and a HPLMN in roaming scenarios. The SEPP that is on
the NF service consumer side is called the c-SEPP and the SEPP that is on the NF service producer is called the p-
SEPP. The N32 interface can be logically considered as 2 separate interfaces as given below.
- N32-c, a control plane interface between the SEPPs for performing initial handshake and negotiating the
parameters to be applied for the actual N32 message forwarding.
- N32-f, a forwarding interface between the SEPPs which is used for forwarding the communication between the
NF service consumer and the NF service producer after applying application level security protection.
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4.2.2 N32-c Interface
The following figure shows the scope of the N32-c interface.

SEPP in SEPP in
N32-c
PLMN A PLMN B
Figure 4.2.2-1: N32-c Interface
The N32-c interface provides the following functionalities:
- Initial handshake procedure between the SEPP in PLMN A (called the initiating SEPP) and the SEPP in PLMN
B (called the responding SEPP), that involves capability negotiation and parameter exchange as specified in
3GPP TS 33.501 [6].
4.2.3 N32-f Interface
The following figure shows the scope of the N32-f interface.

SEPP in SEPP in
PLMN A PLMN B
IPX IPX
(PLMN A (PLMN B
N32-f N32-f N32-f
Side) Side)
Figure 4.2.3-1: N32-f Interface
The N32-f interface shall be used to forward the HTTP/2 messages of the NF service producers and the NF service
consumers in different PLMN, through the SEPPs of the respective PLMN. The application layer security protection
functionality of the N32-f is used only if the PRotocol for N32 INterconnect Security (PRINS) is negotiated between
the SEPPs using N32-c.
The N32-f interface provides the following application layer security protection functionalities:
- Message protection of the information exchanged between the NF service consumer and the NF service producer
across PLMNs by applying application layer security mechanisms as specified in 3GPP TS 33.501 [6].
- Forwarding of the application layer protected message from a SEPP in one PLMN to a SEPP in another PLMN.
Such forwarding may involve IPX providers on path.
- If IPX providers are on the path from SEPP in PLMN A to SEPP in PLMN B, the forwarding on the N32-f
interface may involve the insertion of content modification instructions which the receiving SEPP applies after
verifying the integrity of such modification instructions.
If TLS is the negotiated security policy between the SEPP, then the N32-f shall involve only the forwarding of the
HTTP/2 messages of the NF service producers and the NF service consumers without any reformatting.
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4.3 Protocol Stack
4.3.1 General
The protocol stack for the N32 interface is shown below in Figure 4.2.1-1
Application
HTTP/2
TLS
TCP
IP
L2
Figure 4.3.1-1: N32 Protocol Stack
The N32 interfaces (N32-c and N32-f) use HTTP/2 protocol (see clause 4.2.2) with JSON (see clause 4.2.4) as the
application layer serialization protocol. For the security protection at the transport layer, the SEPPs shall support TLS as
specified in 3GPP TS 33.501 [6].
For the N32-f interface, the application layer (i.e the JSON payload) encapsulates the complete HTTP/2 message
between the NF service consumer and the NF service producer, by transforming the HTTP/2 headers and the body into
specific JSON attributes as specified in clause 6.2.
4.3.2 HTTP/2 Protocol
4.3.2.1 General
HTTP/2 as described in IETF RFC 7540 [7] shall be used for N32 interface.
4.3.2.2 HTTP standard headers
The HTTP request standard headers and the HTTP response standard headers that shall be supported on the N32
interface are defined in Table 4.2.2.2-1 and in Table 4.2.2.2-2 respectively.
Table 4.3.2.2-1: Mandatory to support HTTP request standard headers
Name Reference Description
Accept IETF RFC 7231 [9] This header is used to specify response media types that are
acceptable.
Accept-Encoding IETF RFC 7231 [9] This header may be used to indicate what response content-
encodings (e.g gzip) are acceptable in the response.
Content-Length IETF RFC 7230 [10] This header is used to provide the anticipated size, as a decimal
number of octets, for a potential payload body.
Content-Type IETF RFC 7231 [9] This header is used to indicate the media type of the associated
representation.
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Table 4.3.2.2-2: Mandatory to support HTTP response standard headers
Name Reference Description
Content-Length IETF RFC 7230 [10] This header may be used to provide the anticipated size, as a
decimal number of octets, for a potential payload body.
Content-Type IETF RFC 7231 [9] This header shall be used to indicate the media type of the
associated representation.
Content-Encoding IETF RFC 7231 [9] This header may be used in some responses to indicate to the
HTTP/2 client the content encodings (e.g gzip) applied to the
response body beyond those inherent in the media type.

4.3.2.3 HTTP custom headers
The HTTP custom headers specified in clause 5.2.3 of 3GPP TS 29.500 [4] shall be supported on the N32 interface.
4.3.2.4 HTTP/2 connection management
Each SEPP initiates HTTP/2 connections towards its peer SEPP for the following purposes
- N32-c interface
- N32-f interface
The scope of the HTTP/2 connection used for the N32-c interface is short-lived. Once the initial handshake is
completed the connection is torn down as specified in 3GPP TS 33.501 [6]. The HTTP/2 connection used for N32-c is
end to end between the SEPPs and does not involve an IPX to intercept the HTTP/2 connection, though an IPX may be
involved for IP level routing.
The scope of the HTTP/2 connection used for the N32-f interface is long-lived. The N32-f HTTP/2 connection at a
SEPP can be:
- Case A: Towards a SEPP of another PLMN without involving any IPX intermediaries; or
- Case B: Towards a SEPP of another PLMN via IPX. In this case the HTTP/2 connection from a SEPP terminates
at the next hop IPX with the IPX acting as a HTTP proxy.
For the N32-f interface the HTTP/2 connection management requirements specified in clause 5.2.6 of
3GPP TS 29.500 [4] shall be applicable. The URI scheme used for the N32-f JOSE protected message forwarding API
shall be "http". If confidentiality protection of all IEs for the N32-f JOSE protected message forwarding procedure is
required, then:
- For case A, the security between the SEPPs shall be ensured by means of IPSec or TLS VPN;
- For case B, hop-by-hop security between the SEPP and the IPXs should be established on N32-f. This hop-by-
hop security shall be established using an IPSec or TLS VPN.
4.3.3 Transport Protocol
The Transmission Control Protocol as described in IETF RFC 793 [11] shall be used as transport protocol as required
by HTTP/2 (see IETF RFC 7540 [7]). When there is no IPX between the SEPPs, TLS shall be used for security
protection (see 3GPP TS 33.501 [6]). When there is IPX between the SEPPs, TLS should be used for security protection
as specified in 3GPP TS 33.501 [6].
NOTE: When using TCP as the transport protocol, an HTTP/2 connection is mapped to a TCP connection.
4.3.4 Serialization Protocol
The JavaScript Object Notation (JSON) format as described in IETF RFC 8259 [8] shall be used as the serialization
protocol.
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5 N32 Procedures
5.1 Introduction
The procedures on the N32 interface are split into two categories:
- Procedures that happen end to end between the SEPPs on the N32-c interface;
- Procedures that are used for the forwarding of messages on the service based interface between the NF service
consumer and the NF service producer via the SEPP across the N32-f interface.
5.2 N32 Handshake Procedures (N32-c)
5.2.1 General
The N32 handshake procedure is used between the SEPPs in two PLMNs to mutually authenticate each other and
negotiate the security mechanism to use over N32-f along with associated security configuration parameters.
A HTTP/2 connection shall be established between the initiating SEPP and the responding SEPP end to end over TLS.
The following N32 handshake procedures are specified in the clauses bel
...