C.2 MCPTT-2, MCVideo-2, MCData-2 and CSC-13 interfaces

29.2833GPPDiameter data management applicationsRelease 17TS

C.2.1 General

The Diameter message priority mechanism is an optional feature.

It is recommended to make use of IETF RFC 7944 [8] over the MCPTT-2, MCVideo-2, MCData-2 and CSC-13 interfaces of an operator network when the overload control defined in Annex A is applied on these interfaces.

C.2.2 MC Service Server and Configuration Management Server behaviour

When the MCPTT Server or the Configuration Management Server support the Diameter message priority mechanism, the MCPTT Server or the Configuration Management Server shall comply with IETF RFC 7944 [8].

The MCPTT Server or the Configuration Management Server sending a request shall determine the required priority according to its policies. When priority is required, the MCPTT Server or the Configuration Management Server shall include the DRMP AVP indicating the required priority level in the request it sends and shall prioritise the request according to the required priority level.

When the MCPTT Server or the Configuration Management Server receives the corresponding response, it shall prioritise the received response according to the priority level received within the DRMP AVP if present, in the response, otherwise according to the priority level of the corresponding request.

When the MCPTT Server or the Configuration Management Server receives a request, it shall handle the request according to the received DRMP AVP priority level. For the response, the MCPTT Server or the Configuration Management Server may modify the priority level received in the DRMP AVP according to its policies and shall handle the response according to the required priority level. If the required priority level is different from the priority level received in the request, the MCPTT Server or the Configuration Management Server shall include the DRMP AVP in the response.

If:

– the MCPTT Server and the Configuration Management Server supports using the Diameter message priority mechanism for DSCP marking purposes,

– the transport network utilizes DSCP marking, and

– message-dependant DSCP marking is possible for the protocol stack transporting Diameter,

then the MCPTT Server and the Configuration Management Server shall set the DSCP marking for transport of the request or response according to the required priority level.

Diameter requests related to priority traffic (e.g. MCPTT emergency call) shall contain a DRMP AVP with a high priority of which the level value is operator dependent.

When not-explicitly requested, the inclusion and priority value of the DRMP AVP in Diameter messages are implementation specific.

C.2.3 MC Service User Database behaviour

When the MCPTT User Database supports the Diameter message priority mechanism, the MCPTT User Database shall comply with IETF RFC 7944 [8].

The MCPTT User Database sending a request shall determine the required priority according to its policies. When priority is required, the MCPTT User Database shall include the DRMP AVP indicating the required priority level in the request it sends, and shall prioritise the requests according to required priority level.

When the MCPTT User Database receives the corresponding response, it shall prioritise the received response according to the priority level received within the DRMP AVP if present in the response, otherwise according to the priority level of the corresponding request.

When the MCPTT User Database receives a request, it shall handle the request according to the received DRMP AVP priority level. For the response, it may modify the priority level received in the DRMP AVP according to its policies and shall handle the response according to the required priority level. If the required priority level is different from the priority level received in the request, it shall include the DRMP AVP in the response.

If:

– the MCPTT User Database supports using the Diameter message priority mechanism for DSCP marking purposes,

– the transport network utilizes DSCP marking, and

– message-dependant DSCP marking is possible for the protocol stack transporting Diameter,

then the MCPTT User Database shall set the DSCP marking for transport of the request or response according to the required priority level.

When not explicitly requested, the inclusion and priority value of the DRMP AVP in Diameter messages are implementation specific.

Annex D (normative):
Diameter load control mechanism