Pending Answer Timer

A Pending Answer Timer limits the time that Diameter will wait for an Answer response after forwarding a Request message to an upstream Peer Node. The timer is started when Diameter queues a Request message for forwarding on a Diameter connection, and the timer is stopped when an Answer response to the message is received by Diameter.

When the time limit is exceeded, Diameter will invoke one of the following methods of message rerouting:

One or more Pending Answer Timers can be configured; each Pending Answer Timer can be configured to be assigned to an egress Peer Node to be used for a forwarded transaction. The Default Pending Answer Timer, is available to be used if no other Pending Answer Timer selection rule takes precedence.

In many cases, the Pending Answer Timer used by DSR is based on Diameter client response time requirements. Different Diameter clients for a single Application-ID can have differing response time requirements. The DSR Pending Answer Timer can be controlled based on Ingress Peer Node.

A Pending Answer Timer can be associated with:

The Peer Node that the Request is sent to
The configured Diameter Application Id that is contained in the Request message header
A Routing Option Set

If Pending Answer Timers are associated with both the Peer Node and the Application Id, the one associated with the Peer Node takes precedence. If neither the Peer Node nor the Application Id have an associated Pending Answer Timer, then the Default Pending Answer Timer is used.

When forwarding a Request upstream, the Diameter Routing Function determines the Pending Answer Timer to be used as follows:

If a Routing Option Set is configured for the Ingress Peer Node and Pending Answer Timer is configured in the Routing Option Set
Use Ingress Peer Node Routing Option Set Pending Answer Timer
Else If a Pending Answer Timer is configured for the Egress Peer Node
Use Egress Peer Node Pending Answer Timer
Else If a configured Application-ID exists for the Application-ID in the Request
Use Application-ID Pending Answer Timer
Else
Use the system Default Pending Answer Timer