Inbound Message Retransmission

At each N4 and GTP endpoint, there’s a set of queues for incoming and outgoing traffic. Each queue has a dispatcher thread running that pulls the message from the queue. It dispatches the message to the application for further processing.

Each dispatcher references a retransmission cache to check if the incoming request is already in service. It further performs the following actions:

  • If it’s a retry request, the dispatcher drops the incoming request.

  • If the retransmission cache reaches the threshold for outstanding requests, the incoming request is dropped.

Each dispatcher has a separate retransmission cache. This cache is also updated with the response of the request sent. It’s for the retransmission request received after the response is sent.