6.9 Procedures at the MCVideo gateway

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

6.9.1 General

As described in clause 5.5, the MCVideo gateway servers are inserted in the path between MCVideo functions that reside in MCVideo systems from different trust domains.

This clause specifies the behavior of an MCVideo gateway server that acts as an exit point from an MCVideo system or as an entry point in an MCVideo system.

Local policies enforcement covers a wide variety of actions that are left to implementation. An example of local policies enforcement is given in clause 6.9.4.

6.9.2 MCVideo gateway server acting as an exit point from an MCVideo system

When acting as an exit point from a local MCVideo system to an interconnected MCVideo system, the MCVideo gateway server receives SIP requests and SIP responses intended for the controlling, non-controlling or participating function in the interconnected MCVideo system.

When receiving an outgoing SIP message, the MCVideo gateway server acting as an exit point:

1) shall identify the MCVideo system identity of the interconnected MCVideo system from the information elements in the outgoing SIP message, e.g. Request-URI;

2) may enforce local policy, and if local policy enforcement results in rejecting a SIP request (e.g. not having a mutual aid relationship), the MCVideo gateway shall reject the request by sending back a SIP 403 (Forbidden) response including a warning text "1xx service not authorized with the interconnected system", and the MCVideo gateway server shall not continue with the rest of the steps;

3) may replace in the outgoing SIP message any addressing information linked to the local MCVideo system topology with its own addressing information. This includes;

a) the P-Asserted-Identity header field may be set to the MCVideo gateway server’s own URI; and

b) the Request-URI may be set to the public service identity of the targeted function in the interconnected MCVideo system, or to the URI of the MCVideo gateway server that acts as an entry point in the interconnected MCVideo system; and

NOTE: How the MCVideo gateway server determines the public service identity of the targeted MCVideo function in the interconnected MCVideo system or the URI of the MCVideo gateway server in the interconnected MCVideo system is out of the scope of the present document.

4) shall forward the outgoing SIP message according to 3GPP TS 24.229 [11].

6.9.3 MCVideo gateway server acting as an entry point in an MCVideo system

When acting as an entry point in an MCVideo system from an interconnected MCVideo system, the MCVideo gateway receives SIP requests and SIP responses intended for the controlling, non-controlling or participating function in the local MCVideo system.

When receiving an incoming SIP message, the MCVideo gateway server acting as an entry point:

1) shall identify the MCVideo system identity of the interconnected MCVideo system from the P-Asserted-Identity header field of the incoming SIP messages;

2) may enforce local policy and. if local policy enforcement results in rejecting a SIP request (e.g. not having a mutual aid relationship), the MCVideo gateway shall reject the request by sending back a SIP 403 (Forbidden) response including a warning text "180 service not authorized by the interconnected system", and the MCVideo gateway server shall not continue with the rest of the steps;

3) should replace in the incoming SIP message its own addressing information with the addressing information of the targeted MCVideo function in the local MCVideo system:

a) the Request-URI should be set to the public service identity of the targeted MCVideo function in the local MCVideo system; and

NOTE: How the MCVideo gateway server determines the public service identity of the targeted MCVideo function in the local MCVideo system is out of the scope of the present document.

4) shall forward the incoming SIP message according to 3GPP TS 24.229 [11].

6.9.4 Local policies enforcement

Below is one example of local policy enforcement that can be handled by an MCVideo gateway server.

If an MCVideo gateway server acting as an exit point receives a SIP request or a SIP response that contains sensitive information that cannot be exposed to the targeted interconnected system based on local policies but does not prevent the service from being delivered (e.g. a functional alias), the MCVideo gateway server can remove that information from the outgoing SIP message before forwarding it.