6.6 Namf_MBSCommunication Service API

29.5183GPP5G SystemAccess and Mobility Management ServicesRelease 18Stage 3TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

6.6.1 API URI

The Namf_MBSCommunication service shall use the Namf_MBSCommunication API.

The API URI of the Namf_ MBSCommunication API shall be:

{apiRoot}/<apiName>/<apiVersion>

The request URI used in HTTP requests from the NF service consumer towards the NF service producer shall have the Resource URI structure defined in clause 4.4.1 of 3GPP TS 29.501 [5], i.e.:

{apiRoot}/<apiName>/<apiVersion>/<apiSpecificResourceUriPart>

with the following components:

– The {apiRoot} shall be set as described in 3GPP TS 29.501 [5].

– The <apiName> shall be "namf-mbs-comm".

– The <apiVersion> shall be "v1".

– The <apiSpecificResourceUriPart> shall be set as described in clause 6.6.3.

6.6.2 Usage of HTTP

6.6.2.1 General

HTTP/2, as defined in IETF RFC 7540 [19], shall be used as specified in clause 5 of 3GPP TS 29.500 [4].

HTTP/2 shall be transported as specified in clause 5.3 of 3GPP TS 29.500 [4].

HTTP messages and bodies for the Namf_MBSCommunication service shall comply with the OpenAPI [23] specification contained in Annex A.

6.6.2.2 HTTP standard headers

6.6.2.2.1 General

The usage of HTTP standard headers shall be supported as specified in clause 5.2.2 of 3GPP TS 29.500 [4].

6.6.2.2.2 Content type

The following content types shall be supported:

– JSON, as defined in IETF RFC 8259 [8], shall be used as content type of the HTTP bodies specified in the present specification as indicated in clause 5.4 of 3GPP TS 29.500 [4].

– The Problem Details JSON Object (IETF RFC 7807 [36]). The use of the Problem Details JSON object in a HTTP response body shall be signalled by the content type "application/problem+json".

Multipart messages shall also be supported (see clause 6.6.2.4) using the content type "multipart/related", comprising:

– one JSON body part with the "application/json" content type; and

– one binary body part with 3gpp vendor specific content subtypes.

The 3gpp vendor specific content subtypes defined in Table 6.6.2.2.2-1 shall be supported.

Table 6.6.2.2.2-1: 3GPP vendor specific content subtypes

content subtype	Description
vnd.3gpp.ngap	Binary encoded payload, encoding NG Application Protocol (NGAP) IEs, as specified in clause 9.3 of 3GPP TS 38.413 [9] (ASN.1 encoded).
NOTE: Using 3GPP vendor content subtypes allows to describe the nature of the opaque payload (i.e. NGAP information) without having to rely on metadata in the JSON payload.

See clause 6.6.2.4 for the binary payloads supported in the binary body part of multipart messages.

6.6.2.3 HTTP custom headers

6.6.2.3.1 General

In this release of this specification, no custom headers specific to the Namf_MBSCommunication service are defined. For 3GPP specific HTTP custom headers used across all service-based interfaces, see clause 5.2.3 of 3GPP TS 29.500 [4].

6.6.2.4 HTTP multipart messages

HTTP multipart messages shall be supported, to transfer opaque N2 Information MBS, in the following service operations (and HTTP messages):

– N2MessageTransfer Request and Response (POST).

HTTP multipart messages shall include one JSON body part and one binary body part comprising:

– N2 payload (see clause 6.1.6.4).

The JSON body part shall be the "root" body part of the multipart message. It shall be encoded as the first body part of the multipart message. The "Start" parameter does not need to be included.

The multipart message shall include a "type" parameter (see IETF RFC 2387 [9]) specifying the media type of the root body part, i.e. "application/json".

NOTE: The "root" body part (or "root" object) is the first body part the application processes when receiving a multipart/related message, see IETF RFC 2387 [9]. The default root is the first body within the multipart/related message. The "Start" parameter indicates the root body part, e.g. when this is not the first body part in the message.

For each binary body part in a HTTP multipart message, the binary body part shall include a Content-ID header (see IETF RFC 2045 [10]), and the JSON body part shall include an attribute, defined with the RefToBinaryData type, that contains the value of the Content-ID header field of the referenced binary body part.

6.6.3 Resources

6.6.3.1 Overview

Figure 6.6.3.1-1 describes the resource URI structure of the Namf_MBSCommunication API.

Figure 6.6.3.1-1: Resource URI structure of the Namf_MBSCommunication API

Table 6.6.3.1-1 provides an overview of the resources and applicable HTTP methods.

Table 6.6.3.1-1: Resources and methods overview

Resource name

Resource URI

HTTP method or custom operation

Description

(service operation)

N2 Message Handler (Custom Operation)

/n2-messages/transfer

transfer
(POST)

N2MessageTransfer

6.6.3.1 Resource: N2 Message Handler (Custom Operation)

6.6.3.1.1 Description

This resource represents the N2 Message Handler used to transfer a N2 message related to support a Multicast MBS session towards NG-RANs.

6.6.3.1.2 Resource Definition

Resource URI: {apiRoot}/namf-comm/<apiVersion>/n2-messages

This resource shall support the resource URI variables defined in table 6.6.3.1.2-1.

Table 6.6.3.1.2-1: Resource URI variables for this resource

Name	Data Type	Definition
apiRoot	String	See clause 6.6.1
apiVersion	String	See clause 6.6.1.

6.6.3.1.3 Resource Standard Methods

There are no resource standard methods for the N2 Message Handler resource in this release of this specification

6.6.3.1.4 Resource Custom Operations

6.6.3.1.4.1 Overview

Table 6.6.3.1.4.1-1: Custom operations

Operation Name

Custom operaration URI

Mapped HTTP method

Description

(service operation)

transfer

/n2-messages/transfer

POST

N2MessageTransfer

6.6.3.1.4.2 Operation: transfer

6.6.3.1.4.2.1 Description

The /n2-messages/transfer custom operation is used to initiate the transfer of N2 MBS Session Management information to the NG-RAN nodes serving a multicast MBS session. This custom operation uses the HTTP POST method.

6.6.3.1.4.2.2 Operation Definition

This operation shall support the request data structures specified in table 6.6.3.1.4.2-1 and the response data structure and response codes specified in table 6.6.3.1.4.2-2.

Table 6.6.3.1.4.2.2-1: Data structures supported by the POST Request Body on this resource

Data type	P	Cardinality	Description
MbsN2MessageTransferReqData	M	1	Representation of the data related to a multicast MBS session to be sent to the NG-RAN node(s) by the AMF.

Table 6.6.3.1.4.2.2-2: Data structures supported by the POST Response Body on this resource

Data type	P	Cardinality	Response codes	Description
MbsN2MessageTransferRspData	M	1	200 OK	Indicates that the AMF has successfully initiated the transfer of N2 Information to the AN.
RedirectResponse	O	0..1	307 Temporary Redirect	Temporary redirection. The response shall include a Location header field containing a different URI, or the same URI if a request is redirected to the same target resource via a different SCP. In the former case, the URI shall be an alternative URI of the resource located on an alternative service instance within the same AMF or AMF (service) set.
RedirectResponse	O	0..1	308 Permanent Redirect	Permanent redirection. The response shall include a Location header field containing a different URI, or the same URI if a request is redirected to the same target resource via a different SCP. In the former case, the URI shall be an alternative URI of the resource located on an alternative service instance within the same AMF or AMF (service) set.
ProblemDetails	O	0..1	404 Not Found	When the MBS Session ID is not found in the NF Service Producer (i.e. AMF) the "cause" attribute shall be set to: – MBS_SESSION_NOT_FOUND See table 6.6.7.3-1 for the description of these errors
NOTE: The mandatory HTTP error status code for the POST method listed in Table 5.2.7.1-1 of 3GPP TS 29.500 [4] also apply, with response body containing an object of ProblemDetails data type (see clause 5.2.7 of 3GPP TS 29.500 [4]).

Table 6.6.3.1.4.2.2-3: Headers supported by the 307 Response Code on this resource

Name

Data type

Cardinality

Description

Location

string

An alternative URI of the resource located on an alternative service instance within the same AMF or AMF (service) set.

Or the same URI, if a request is redirected to the same target resource via a different SCP.

3gpp-Sbi-Target-Nf-Id

string

0..1

Identifier of the target NF (service) instance ID towards which the request is redirected

Table 6.6.3.1.4.2.2-4: Headers supported by the 308 Response Code on this resource

Name

Data type

Cardinality

Description

Location

string

An alternative URI of the resource located on an alternative service instance within the same AMF or AMF (service) set.

Or the same URI, if a request is redirected to the same target resource via a different SCP.

3gpp-Sbi-Target-Nf-Id

string

0..1

Identifier of the target NF (service) instance ID towards which the request is redirected

6.6.4 Custom Operations without associated resources

6.6.5 Notifications

6.6.5.1 General

The notifications provided by the Namf_MBSCommunication service are specified in this clause.

Table 6.6.5.1-1: Callback overview

Notification

Resource URI

HTTP method or custom operation

Description

(service operation)

Notification

{notifyUri}

POST

Notify

6.6.5.2 Notification

6.6.5.2.1 Description

The notification is used by the AMF to report the failure of an MBS related N2 procedure with an NG-RAN node to a NF service consumer.

6.6.5.2.2 Notification Definitionn

The Callback URI "{notifyUri}" shall be used with the callback URI variables defined in table 6.6.5.2.2-1.

Table 6.6.5.2.2-1: Callback URI variables

Name	Definition
notifyUri	String formatted as URI with the Callback URI

6.6.5.2.3 Notification Standard Methods

6.6.5.2.3.1 POST

This method shall support the request data structures specified in table 6.6.5.2.3.1-1 and the response data structures and response codes specified in table 6.6.5.2.3.1-2.

Table 6.6.5.2.3.1-2: Data structures supported by the POST Request Body

Data type	P	Cardinality	Description
Notification	M	1	Represents the notification to be delivered

Table 6.6.5.2.3.1-3: Data structures supported by the POST Response Body

Data type	P	Cardinality	Response codes	Description
n/a			204 No Content
RedirectResponse	O	0..1	307 Temporary Redirect	Temporary redirection. The NF service consumer shall generate a Location header field containing a URI pointing to the endpoint of another NF service consumer to which the notification should be sent. If an SCP redirects the message to another SCP then the location header field shall contain the same URI or a different URI pointing to the endpoint of the NF service consumer to which the notification should be sent.
RedirectResponse	O	0..1	308 Permanent Redirect	Permanent redirection. The NF service consumer shall generate a Location header field containing a URI pointing to the endpoint of another NF service consumer to which the notification should be sent. If an SCP redirects the message to another SCP then the location header field shall contain the same URI or a different URI pointing to the endpoint of the NF service consumer to which the notification should be sent.
NOTE: The mandatory HTTP error status code for the POST method listed in Table 5.2.7.1-1 of 3GPP TS 29.500 [4] also apply, with response body containing an object of ProblemDetails data type (see clause 5.2.7 of 3GPP TS 29.500 [4]).

Table 6.6.5.2.3.1-4: Headers supported by the 307 Response Code on this resource

Name	Data type	P	Cardinality	Description
Location	string	M	1	A URI pointing to the endpoint of the NF service consumer to which the notification should be sent
3gpp-Sbi-Target-Nf-Id	string	O	0..1	Identifier of the target NF (service) instance ID towards which the request is redirected

Table 6.6.5.2.3.1-5: Headers supported by the 308 Response Code on this resource

Name	Data type	P	Cardinality	Description
Location	string	M	1	A URI pointing to the endpoint of the NF service consumer to which the notification should be sent
3gpp-Sbi-Target-Nf-Id	string	O	0..1	Identifier of the target NF (service) instance ID towards which the request is redirected

6.6.6 Data Model

6.6.6.1 General

This clause specifies the application data model supported by the API.

Table 6.6.6.1-1 specifies the data types defined for the Namf_MBSCommunication service based interface protocol.

Table 6.6.6.1-1: Namf_MBSCommunication specific Data Types

Data type	Clause defined	Description
MbsN2MessageTransferReqData	6.6.6.2.2	Data within MBS N2 Message Transfer Request
MbsN2MessageTransferRspData	6.6.6.2.3	Data within MBS N2 Message Transfer Response
N2MbsSmInfo	6.6.6.2.4	N2 MBS Session Management Information
Notification	6.6.6.2.5	Data within Notify Request
RanFailure	6.6.6.2.6	Description of an NG RAN failure
MbsNgapIeType	6.6.6.3.3	NGAP Information Element Type for MBS
RanFailureIndication	6.6.6.3.4	NG RAN failure indication

Table 6.6.6.3-2 specifies data types re-used by the Namf_MBSCommunication service based interface protocol from other specifications, including a reference to their respective specifications and when needed, a short description of their use within the Namf_MBSCommunication service based interface.

Table 6.6.6.1-2: Namf_MBSCommunication re-used Data Types

Data type	Reference	Comments
ProblemDetails	3GPP TS 29.571 [6]	Common data type used in response bodies
supportedFeatures	3GPP TS 29.571 [6]	Supported Features
RedirectResponse	3GPP TS 29.571 [6]	Response body of the redirect response message
MbsSessionId	3GPP TS 29.571 [6]	MBS Session Identifier
NgApCause	3GPP TS 29.571 [6]	NGAP Cause
N2InformationTransferResult	6.1.6.3.8	Enumeration N2 Message Transfer Result

6.6.6.2 Structured data types

6.6.6.2.1 Introduction

Structured data types used in Namf_MBSCommunication service are specified in this clause.

6.6.6.2.2 Type: MbsN2MessageTransferReqData

Table 6.6.6.2.2-1: Definition of type MbsN2MessageTransferReqData

Attribute name	Data type	P	Cardinality	Description	Applicability
mbsSessionId	MbsSessionId	M	1	This IE shall be included to identify the MBS session to which the N2 information to be transferred is related.
areaSessionId	AreaSessionId	O	0..1	Area Session ID This IE may be present, if this is a Location dependent multicast MBS session.
n2MbsSmInfo	N2MbsSmInfo	M	1	This IE shall contain the N2 MBS Session Information to be transferred to the NG-RAN nodes serving the MBS session and additional information required for the processing of the message by the AMF.
supportedFeatures	SupportedFeatures	C	0..1	This IE shall be present if at least one optional feature defined in clause 6.1.8 is supported.
ranNodeIdList	array(GlobalRanNodeId)	O	1..N	When present, this IE shall contain the list of NG RAN Node IDs towards which the MBS related N2 message is requested to be distributed.	RAN-ID-LIST
notifyUri	Uri	O	0..1	When present, this IE shall contain the notification URI to be used for receiving notifications about possible failures of the MBS related N2 procedure with an NG RAN node in the ranNodeIdList.	RAN-ID-LIST
notifyCorrelationId	string	O	0..1	When present, this IE shall contain the notification correlation ID to be sent within notifications.	RAN-ID-LIST

6.6.6.2.3 Type: MbsN2MessageTransferRspData

Table 6.6.6.2.3-1: Definition of type MbsN2MessageTransferRspData

Attribute name	Data type	P	Cardinality	Description
result	N2InformationTransferResult	M	1	This IE shall provide the result of the MBS N2 information transfer processing at the AMF.
supportedFeatures	SupportedFeatures	C	0..1	This IE shall be present if at least one optional feature defined in clause 6.1.8 is supported.
failureList	array(RanFailure)	O	1..N	List of MBS related N2 procedure failures

6.6.6.2.4 Type: N2MbsSmInfo

Table 6.6.6.2.4-1: Definition of type N2MbsSmInfo

Attribute name	Data type	P	Cardinality	Description
ngapIeType	MbsNgapIeType	M	1	This IE shall indicate the NGAP IE type of the ngapData as specified in clause 6.6.6.4.2.2.
ngapData	RefToBinaryData	M	1	This IE shall contain the reference the binary data part carrying the NGAP data.

6.6.6.2.5 Type: Notification

Table 6.6.6.2.5-1: Definition of type Notification

Attribute name	Data type	P	Cardinality	Description
mbsSessionId	MbsSessionId	M	1	MBS Session ID
areaSessionId	AreaSessionId	C	0..1	Area Session ID This IE shall be present, if present in the N2Message Transfer request.
failureList	array(RanFailure)	M	1..N	List of MBS related N2 procedure failures
notifyCorrelationId	string	C	0..1	This IE shall be present if the same IE is present in the N2Message Transfer request. When present, it shall contain the same value as received in the request.

6.6.6.2.6 Type: RanFailure

Table 6.6.6.2.6-1: Definition of type RanFailure

Attribute name	Data type	P	Cardinality	Description
ranId	GlobalRanNodeId	M	1	Indicates the identity of the NG RAN node.
ranFailureCause	NgApCause	C	0..1	When present, this IE shall contain the NGAP failure cause received from the NG-RAN. (NOTE)
ranFailureIndication	RanFailureIndication	C	0..1	This IE shall be present if the AMF cannot deliver the MBS related N2 message to the NG-RAN node. (NOTE)
NOTE: Either the ranFailureCause IE or the ranFailureIndication IE shall be present.

6.6.6.3 Simple data types and enumerations

6.6.6.3.1 Introduction

This clause defines simple data types and enumerations that can be referenced from data structures defined in the previous clauses.

6.6.6.3.2 Simple data types

The simple data types defined in Table 6.6.6.3.2-1 shall be supported.

6.6.6.3.3 Enumeration: MbsNgapIeType

Table 6.6.6.3.3-1: Enumeration MbsNgapIeType

Enumeration value	Description
"MBS_SES_ACT_REQ"	Multicast Session Activation Request Transfer
"MBS_SES_DEACT_REQ"	Multicast Session Deactivation Request Transfer
"MBS_SES_UPD_REQ"	Multicast Session Update Request Transfer

6.6.6.3.4 Enumeration: RanFailureIndication

The enumeration RanFailureIndication indicates a NG-RAN failure event.

Table 6.5.6.3.4-1: Enumeration RanFailureIndication

Enumeration value	Description
"NG_RAN_FAILURE_WITHOUT_RESTART"	The NG-RAN node failed without restart.
"NG_RAN_NOT_REACHABLE"	The AMF cannot reach the NG RAN node when sending the MBS related N2 message.

6.6.6.4 Binary data

6.6.6.4.1 Introduction

This clause defines the binary data that shall be supported in a binary body part in an HTTP multipart message (see clauses 6.6.2.2.2 and 6.6.2.4).

Table 6.6.6.4.1-1: Binary Data Types

Name	Clause defined	Content type
N2 MBS Session Management Information	6.6.6.4.2	vnd.3gpp.ngap

6.6.6.4.2 N2 Information

6.6.6.4.2.1 Introduction

N2 Information shall encode NG Application Protocol (NGAP) IEs, as specified in clause 9.3.A of 3GPP TS 38.413 [12] (ASN.1 encoded), using the vnd.3gpp.ngap content-type.

6.6.6.4.2.2 NGAP IEs

N2 Information may encode following NGAP MB-SMF related IE specified in in clause 9.3.5 of 3GPP TS 38.413 [12], as summarized in Table 6.6.6.4.2.2-1.

Table 6.6.6.4.2.2-1: N2 Information content for class MBS-SM

NGAP IE	Reference (3GPP TS 38.413 [12])	Related NGAP message
Multicast Session Activation Request Transfer	9.3.5.11	MULTICAST SESSION ACTIVATION REQUEST
Multicast Session Deactivation Request Transfer	9.3.5.12	MULTICAST SESSION DEACTIVATION REQUEST
Multicast Session Update Request Transfer	9.3.5.13	MULTICAST SESSION UPDATE REQUEST

6.6.7 Error Handling

6.6.7.1 General

HTTP error handling shall be supported as specified in clause 5.2.4 of 3GPP TS 29.500 [4].

6.6.7.2 Protocol Errors

Protocol Error Handling shall be supported as specified in clause 5.2.7 of 3GPP TS 29.500 [4].

6.6.7.3 Application Errors

The common application errors defined in the Table 5.2.7.2-1 in 3GPP TS 29.500 [4] may also be used for the Namf_MBSCommunication service, and the following application errors listed in Table 6.6.7.3-1 are specific for the Namf_MBSCommunication service.

Table 6.6.7.3-1: Application errors

Application Error	HTTP status code	Description
MBS_SESSION_NOT_FOUND	404 Not Found	Indicates the MBS related N2 Message transfer has failed due to the MBS Session ID being unknown to the AMF.

6.6.8 Feature Negotiation

The optional features in table 6.6.8-1 are defined for the Namf_MBSCommunication API. They shall be negotiated using the extensibility mechanism defined in clause 6.6 of 3GPP TS 29.500 [4].

The NF Service Consumer shall indicate the optional features it supports for the Namf_MBSCommunication service, if any, by including the supportedFeatures attribute in payload of the HTTP Request Message for following service operations:

– N2MessageTransfer, as specified in clause 5.7.2.2.

The AMF shall determine the supported features for the service operations as specified in clause 6.6 of 3GPP TS 29.500 [4] and shall indicate the supported features by including the supportedFeatures attribute in payload of the HTTP response for the service operation.

The syntax of the supportedFeatures attribute is defined in clause 5.2.2 of 3GPP TS 29.571 [6].

The following features are defined for the Namf_MBSCommunication service.

Table 6.6.8-1: Features of supportedFeatures attribute used by Namf_MBSCommunication service

Feature Number

Feature

M/O

Description

RAN-ID-LIST

N2 MBS session request distribution with list of NG RAN Node IDs provided by NF Service Consumer to AMF

An NF Service Consumer (e.g. MB-SMF) and an AMF that support this feature shall support:

Namf_MBSCommunication_N2MessageTransfer Request including the list of NG RAN node IDs towards which the MBS related N2 message is requested to be distributed; and
the AMF notifying an MBS related N2 procedure failure with an NG RAN node in this list, detected by the AMF or reported by the NG-RAN node.

See clause 8.4.1.2 of 3GPP TS 23.527 [33] and clauses 5.7.2.2 and 5.7.2.3.

Feature number: The order number of the feature within the supportedFeatures attribute (starting with 1).

Feature: A short name that can be used to refer to the bit and to the feature.

M/O: Defines if the implementation of the feature is mandatory ("M") or optional ("O").

Description: A clear textual description of the feature.

6.6.9 Security

As indicated in 3GPP TS 33.501 [27], the access to the Namf_MBSCommunication API may be authorized by means of the OAuth2 protocol (see IETF RFC 6749 [28]), using the "Client Credentials" authorization grant, where the NRF (see 3GPP TS 29.510 [29]) plays the role of the authorization server.

If Oauth2 authorization is used, an NF Service Consumer, prior to consuming services offered by the Namf_ MBSCommunication API, shall obtain a "token" from the authorization server, by invoking the Access Token Request service, as described in 3GPP TS 29.510 [29], clause 5.4.2.2.

NOTE: When multiple NRFs are deployed in a network, the NRF used as authorization server is the same NRF that the NF Service Consumer used for discovering the Namf_MBSCommunication service.

The Namf_ MBSCommunication API defines scopes for OAuth2 authorization as specified in 3GPP TS 33.501 [27]; it defines a single scope consisting on the name of the service (i.e., "namf-mbs-comm"), and it does not define any additional scopes at resource or operation level.

6.6.10 HTTP redirection

An HTTP request may be redirected to a different AMF service instance, within the same AMF or a different AMF of an AMF set, e.g. when an AMF service instance is part of an AMF (service) set or when using indirect communications (see 3GPP TS 29.500 [4]).

An SCP that reselects a different AMF producer instance will return the NF Instance ID of the new AMF producer instance in the 3gpp-Sbi-Producer-Id header, as specified in clause 6.10.3.4 of 3GPP TS 29.500 [4].

If an AMF within an AMF set redirects a service request to a different AMF of the set using an 307 Temporary Redirect or 308 Permanent Redirect status code, the identity of the new AMF towards which the service request is redirected shall be indicated in the 3gpp-Sbi-Target-Nf-Id header of the 307 Temporary Redirect or 308 Permanent Redirect response as specified in clause 6.10.9.1 of 3GPP TS 29.500 [4].

Annex A (normative):
OpenAPI specification