For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.

For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905. 5GMS ARP BM-SC DASH DTLS FEC GBR HLS MPD QCI QOS QOE ROM RTSP RTP RTCP SACH SAI SCEF SDP TLS TV UE UDP URL UTC

As shown in Figure 4.1-1, the reference point between Content Provider and BM-SC is called the xMB interface. Using the xMB reference point, content provider can invoke procedures supported by BM-SC(s) to set up and manage MBMS user service from BM-SC to the MBMS Clients. BM-SC defines an endpoint with all supported procedures on the xMB interface, which can then be converted to SGmb procedures for the interface between BM-SC and MBMS GW (not depicted).

The BM-SC may forward the received content for unicast delivery for appropriate functions (e.g., MBMS user service fallback). The control plane (xMB-C) and the user plane (xMB-U) may be optionally terminated by 3GPP defined enabler / exposure functions such as an SCEF, which exposes the same or a different interface to content providers. The exposed API such as by SCEF is not specified in the present document. The content provider may optionally exchange application level information like service metadata (e.g. serviceIds or URL(s) of USD(s) or other service identifier(s)) directly with the application. The BM-SC may support CAPIF [10]. When CAPIF is supported, then:

• the BM-SC shall support the CAPIF API provider domain functions (i.e. CAPIF-2/2e (xMB), CAPIF-3, CAPIF-4 and CAPIF-5 as specified in TS 23.222);
• the BM-SC xMB authentication and authorization functions (as defined in Clause 5.2) are replaced by CAPIF equivalent core domain functions (i.e. CAPIF-1/1e).

The CAPIF and associated API provider domain functions are specified in TS 23.222. The content provider may be a mission critical service provider ([12]), which is arranging MC Services to Mission Critical Organizations. Providing MC Services may require additional control of the resource allocation (QoS, coverage area). For this purpose, the interface can be extended with the xMB mission critical extension. The xMB mission critical extension consists in:

• additional properties within the control plane procedures (Table 5.4-6),
• specific semantic and syntax for the geographical area (Clause 5.4.7).

The Content Provider may be a 5GMS Application Provider as defined in clause 4.6 of TS 26.501, providing 5G Media Streaming services to a 5GMS System, as shown in Figure 4.1-2. In this case, Content Receiver <APP> includes a 5GMS Client that can be served at least partially by the MBMS Client. The 5GMS Application Function (5GMS AF) invokes xMB-C control plane procedures on the BM-SC as specified in clauses 5.3 and 5.4 and, as a result, content is ingested by the BM-SC from the 5GMS Application Server (5GMS AS) using the xMB-U File Distribution procedures specified in clause 5.5.2 to support delivery of xMB-C Session types Application or Files. Procedures for 5GMS content delivery via eMBMS, including communication of the 5GMS AF and 5GMS AS with the BM-SC are defined in clause 5.10 of TS 26.501.

The xMB reference point exists between the content provider and the BM-SC directly or via 3GPP defined enabler / exposure functions such as SCEF. When the BM-SC connects to content provider via a 3GPP defined enabler / exposure function, the xMB-C interface (and optionally also the xMB-U) is terminated at the 3GPP defined enabler / exposure function. The xMB reference point provides the ability for the content provider to:

• authenticate and authorize BM-SC(s).
• create, modify and terminate a service.
• create, modify and terminate a session.
• query information.
• deliver content to the BM-SC(s)

The xMB reference point provides the ability for the BM-SC to:

• authenticate and authorize a content provider.
• notify the content provider of the status of an MBMS user service usage.
• retrieve content from the content provider.

The xMB reference point shall support security function for confidentiality protection of both control plane (xMB-C) and user plane (xMB-U).