B.2 T6a, T6ai, T6b, T6bi, T7 interfaces

29.1283GPPMobility Management Entity (MME) and Serving GPRS Support Node (SGSN) interfaces for interworking with packet data networks and applicationsRelease 17TS

The Diameter message priority mechanism is an optional feature which may apply on one or several of the T6a, T6ai, T6b, T6bi, T7 interfaces.

It is recommended to make use of IETF RFC 7944 [15] over the T6a, T6ai, T6b, T6bi, T7 interfaces of an operator network when the overload control defined in Annex A is applied on these interfaces.

A 3GPP functional entity supporting the Diameter message priority mechanism over one or several of the T6a, T6ai, T6b, T6bi, T7 interfaces shall comply with IETF RFC 7944 [15].

A 3GPP functional entity sending a request shall determine the required priority according to its policies. When priority is required, it 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 3GPP functional element 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 a 3GPP functional entity 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:

– a 3GPP functional entity 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 3GPP functional entity shall set the DSCP marking for transport of the request or response according to the required priority level.

The decisions of the 3GPP functional entity for a required priority and for the priority level value are implementation specific.

Diameter requests related to high priority traffic shall contain a DRMP AVP with a high priority of which the level value is operator dependent.

Annex C (normative):
Diameter load control mechanism