Route Selection

The route selection process and its usage in retries are as follows:

  1. There is no requirement for the service to send Destination-Host and Destination-Realm AVPs in CCR.

  2. When there are no Destination fields in a message from the SMF service, the diameter endpoint evaluates the Destination-Host and Destination-Realm from the host selection profile. It associates with the passed client profile in the request.

  3. Host selection profile has a mandatory primary and an optional secondary host-realm pair. While realm is an optional CLI, it sets to a default value.

  4. The host and realm serve as an input to the route search algorithm to find possible multiple matching routes. The order depends on the flag and weight.

  5. Select the peer of the highest ordered active route to send a message. While on delivery failure and on retries configuration, the next route in the sequence is chosen to deliver the message.

  6. When the found routes run through due to failures and higher retry count, it fetches the secondary host to find the next set of ordered routes.

  7. When there are no or failed routes, it drops the request and the service responds accordingly.

  8. In the absence of host selection profile configuration, the peer management module selects and sorts all the active routes in the route table.

  9. For a subsequent CCR-U and CCR-T requests, the service populates a message with Destination-Host and Destination-Realm. It captures the details from the Origin-Host and Origin-Realm respectively from the CCA-I response.

  10. In CCR-U and CCR-T requests, for service with the existing Destination-Host and Destination-Realm, it skips the host selection logic.