5 Functional entities

24.2813GPPMission Critical Video (MCVideo) signalling controlProtocol specificationRelease 18TS

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

5.1 General

This clause associates the functional entities with the MCVideo roles described in the stage 2 architecture document (see 3GPP TS 23.281 [26]).

5.2 MCVideo client

To be compliant with the procedures in the present document, an MCVideo client shall:

– act as the user agent for all MCVideo application transactions (e.g. initiation of a group call); and

– support handling of the MCVideo client ID as described in clause 4.10.

To be compliant with the on-network procedures in the present document, an MCVideo client shall:

– support the MCVideo client on-network procedures defined in 3GPP TS 23.281 [26];

– support the GCS UE procedures defined in 3GPP TS 23.468 [82] for unicast delivery, MBMS delivery and service continuity;

– act as a SIP UA as defined in 3GPP TS 24.229 [11];

– generate SDP offer and SDP answer in accordance with 3GPP TS 24.229 [11] and clause 6.2;

– act as a transmission control participant responsible for transmission control requests and implement the on-network procedures for transmission and reception control requests as specified in 3GPP TS 24.581 [5];

– for registration and service authorisation, implement the procedures specified in clause 7.2;

– for affiliation, implement the procedures specified in clause 8.2;

– for group call functionality (including emergency and imminent peril), implement the MCVideo client procedures specified in clause 9.2; and

– for private call functionality (including emergency), implement the MCVideo client procedures specified in clause 10.2;

– for emergency alert, implement the procedures specified in clause 11.2; and

– for functional alias management, implement the procedures specified in clause 20.2.1.

To be compliant with the off-network procedures in the present document, an MCVideo client shall:

– support the off-network procedures defined in 3GPP TS 23.281 [26];

– support the MONP MCVideo messages specified in clause 17;

– act as a transmission control participant for transmission and reception control requests and implement the off-network procedures for transmission and reception control requests as specified in 3GPP TS 24.581 [5];

– act as a transmission control server providing distributed transmission and reception control and implement the off-network procedures for transmission and reception control as specified in 3GPP TS 24.581 [5];

– implement the procedures for ProSe direct discovery for public safety use as specified in 3GPP TS 24.334 [59];

– implement the procedures for one-to-one ProSe direct communication for Public Safety use as specified in 3GPP TS 24.334 [59];

– for group call functionality (including emergency and imminent peril), implement the MCVideo client procedures specified in clause 9.3; and

– for private call functionality, implement the MCVideo client procedures specified in clause 10.3.

To be compliant with the on-network and off-network procedures in the present document requiring end-to-end private call security key distribution, an MCVideo client shall support the procedures specified in 3GPP TS 33.180 [8].

To be compliant with the procedures for confidentiality protection of XML elements in the present document, the MCVideo client shall implement the procedures specified in clause 6.6.2.

To be compliant with the procedures for integrity protection of XML MIME bodies in the present document, the MCVideo client shall implement the procedures specified in clause 6.6.3.

5.3 MCVideo server

5.3.1 General

An MCVideo server can perform the controlling role for group calls and private calls as defined in 3GPP TS 23.281 [26].

An MCVideo server can perform the participating role for group calls and private calls as defined in 3GPP TS 23.281 [26].

An MCVideo server performing the participating role can serve an originating MCVideo user.

An MCVideo server performing the participating role can serve a terminating MCVideo user.

The same MCVideo server can perform the participating role and controlling role for the same group session.

When referring to the procedures in the present document for the MCVideo server acting in a participating role for the served user, the term, "participating MCVideo function" is used.

When referring to the procedures in the present document for the MCVideo server acting in a controlling role for the served user, the term "controlling MCVideo function" is used.

To be compliant with the procedures in the present document, an MCVideo server shall:

– support the MCVideo server procedures defined in 3GPP TS 23.281 [26];

– implement the role of an AS performing 3rd party call control acting as a routing B2BUA as defined in 3GPP TS 24.229 [11];

– support the GCS AS procedures defined in 3GPP TS 23.468 [82] for unicast delivery, MBMS delivery and service continuity;

– generate SDP offer and SDP answer in accordance with 3GPP TS 24.229 [11] and clause 6.3;

– implement the role of a centralised transmission control server and implement the on-network procedures for transmission and reception control as specified in 3GPP TS 24.581 [5];

– for registration and service authorisation, implement the procedures specified in clause 7.3;

– for affiliation, implement the procedures specified in clause 8.2.2;

– for group call functionality (including emergency and imminent peril), implement the MCVideo server procedures specified in clause 9.2;

– for private call functionality, implement the MCVideo server procedures specified in clause 10.2;

– for priority sharing, implement the MCVideo server procedures in clause 6.7; and

– for functional alias management, implement the procedures specified in clause 20.2.2.

To be compliant with the procedures in the present document requiring the distribution of private call keying material between MCVideo clients as specified in 3GPP TS 33.180 [8], an MCVideo server shall ensure that the keying material is copied from incoming SIP messages into the outgoing SIP messages.

To be compliant with the procedures for confidentiality protection of XML elements in the present document, the MCVideo server shall implement the procedures specified in clause 6.6.2.

To be compliant with the procedures for integrity protection of XML MIME bodies in the present document, the MCVideo server shall implement the procedures specified in clause 6.6.3.

5.3.2 Functional connectivity models

The following figures give an overview of the connectivity between the different functions of the MCVideo server as described in clause 5.3.1.

NOTE: Separate boxes are shown for each of the functions of the MCVideo server. In each MC system, these functions can be physically combined into one MCVideo server or can be implemented on more than one MCVideo server. For example, there could be an instantiation of an MCVideo server that only serves as a controlling MCVideo function, but not as a participating MCVideo function for any MCVideo clients. When an MCVideo server supports more than one function, then sending requests from one function to another does not incur a traversal of the underlying IMS SIP core network.

Figure 5.3.2-1 shows the basic functions of the MCVideo server when operating within the primary MCVideo system.

Figure 5.3.2-1: Functions of the MCVideo server in the primary MC system

Figure 5.3.2-2 shows the roles of the MCVideo server in a mutual aid relationship between a primary MC system and a partner MC system. Here, the controlling MCVideo function is in the primary MC system and the called user is homed in a partner MC system.

Figure 5.3.2-2: Mutual aid relationship between the primary MC system and a partner MC system with the controlling MCVideo function in the primary MC system

Figure 5.3.2-3 shows the roles of the MCVideo server in a mutual aid relationship between a primary MC system and a partner MC system. Here, the controlling MCVideo function is in the partner MC system.

Figure 5.3.2-3: Mutual aid relationship between the primary MC system and a partner MC system with the controlling MCVideo function in the partner MC system

Figure 5.3.2-4 illustrates a functional connectivity model involving multiple partner systems where the partner system that owns the group does not home any of the group members.

Figure 5.3.2-4: : Mutual aid relationship between the primary MC system and more than one partner MC system for MCVideo service

Other functional connectivity models can exist.

5.3.3 Failure case

When initiating a failure response to any received request, depending on operator policy, the MCVideo server may insert a SIP Response-Source header field with an "fe" header field parameter constructed with the URN namespace "urn:3gpp:fe", the fe-id part of the URN set to "as" and the "role" header field parameter set to "pf-mcvideo-server", "cf-mcvideo-server" or "ncf-mcvideo-server" depending on the current role endorsed by the MCVideo server and in accordance with clause 7.2.17 of 3GPP TS 24.229 [11].

5.4 MCVideo UE-to-network relay

To be compliant with the procedures in the present document for service continuity, an MCVideo UE-to-network relay shall support the UE-to-network relay procedures as specified in 3GPP TS 24.334 [59] and 3GPP TS 23.281 [26].

5.5 MCVideo gateway server

5.5.1 General

To allow interconnection between MCVideo systems in different trust domains, MC Gateway Servers can be optionally added on the path between controlling and participating MCVideo functions and between controlling and non-controlling MCVideo functions.

An MCVideo gateway server acts as a SIP and HTTP proxy for signalling with an interconnected MCVideo system in a different trust domain.

An MCVideo gateway server acts as an application and security gateway with an interconnected MCVideo system in a different trust domain.

An MCVideo gateway server provides topology hiding to the interconnected MCVideo system in a different trust domain.

An MCVideo gateway server enforces local policies and local security.

An MCVideo gateway server can be an exit point from the local MCVideo system to an interconnected MCVideo system in a different trust domain, an entry point to the MCVideo system from an interconnected MCVideo system in a different trust domain, or both.

An MCVideo gateway server is transparent to controlling and participating MCVideo functions and to controlling and non-controlling MCVideo functions. When required for interconnection, MC gateway server URIs are known and used by MCVideo servers in place of the PSIs of the interconnected MCVideo server. The MCVideo server does not need to know if it finally addresses directly a controlling MCVideo function or an intermediate MCVideo gateway server.

To be compliant with the procedures in the present document, an MCVideo gateway server shall:

– support the MC gateway server procedures defined in 3GPP TS 23.280 [74] and 3GPP TS 23.281 [26]; and

– support the MC gateway server procedures defined in 3GPP TS 33.180 [8];

– implement the procedures specified in clause 6.9.

To be compliant with the procedures for confidentiality protection in the present document, the MCVideo gateway server shall implement the procedures specified in clause 6.6.2, acting on behalf of the MCVideo server when sending or receiving confidentiality protected content to or from an MCVideo server in another trust domain.

To be compliant with the procedures for integrity protection of XML MIME bodies in the present document, the MCVideo gateway server shall implement the procedures specified in clause 6.6.3, acting on behalf of the MCVideo server when sending or receiving integrity protected content to or from an MCVideo server in another trust domain.