2.6.7 Diameter Routing Message Priority

RFC 7944 Diameter Routing Message Priority (DRMP) is the IETF standard which defines a mechanism to allow Diameter endpoints to indicate the relative priority of Diameter transactions. With this information, Diameter nodes can factor that priority into routing, resource allocation and overload abatement decisions. Message priority is embedded into IETF defined DRMP AVP of diameter messages with priority value ranging from 0 through 15 where 0 is the highest priority value and 15 is the lowest priority value. DRMP allows message priority assignment based on Diameter transactions that is request and answer message shall have same message priority. DSR uses the DRMP AVP based message priorities for message throttling decisions during congestion conditions similar to message priorities defined using Message Priority Configuration Set (MPCS) at DSR.

DSR provides the system configuration option to enable the support for 16 message priorities or legacy 5 message priorities. DRMP feature can be used at DSR only if the support for 16 message priorities has been enabled. DRMP feature can be enabled for individual Diameter Application Ids which allows DSR to assign message priorities to ingress diameter messages based on DRMP AVP only for configured Diameter Application Id’s. If no DRMP AVP is present in the ingress diameter message then message priority shall be assigned based on MPCS configurations at DSR. The operator is also provided a configuration option called “Answer Priority Mode”, a System Options attribute, for selecting which method to use for assigning priority to Answer messages - via the DSR legacy method of reserving the highest priorities for normal Answers (Highest Priority Mode) or the DRMP method of making the Answer priority the same as the Request priority (Request Priority Mode). When Highest Priority Mode is set, DSR ignores DRMP AVPs in Answer messages because the operator has chosen to ignore the DRMP method of assigning priority to Answers.