Pending Answer Timers configuration

A Pending Answer Timer sets the amount of time the DSR waits for an Answer after sending a Request to a Peer Node.

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

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

The Diameter Routing Option Set provides an optional Pending Answer Timer element. If a configured Pending Answer Timer is specified in a Routing Option Set:

Routing Option Set Maximum per Message Forwarding Allowed must be > 1
Routing Option Set Transaction Lifetime must be greater than or equal to the value of the Pending Answer Timer specified for the Routing Option Set

The Routing Option Set Transaction Lifetime value controls the total time that Diameter will attempt to process a transaction, including re-routing attempts. Although the Routing Option Set can be associated with an Ingress Peer Node, Diameter evaluates the Routing Option Set Transaction Lifetime for expiration only at re-routing attempts, which means:

Transaction Lifetime is not applicable or configurable if the Routing Option Set has re-routing disabled (Maximum per Message Forwarding Allowed value is set to 1)
Transaction Lifetime maybe extended by as much as 1 Pending Answer Timer interval in some cases

A Routing Option Set referenced by a Diameter Application-ID entry cannot have a Pending Answer Timer configured, because each Diameter Application-ID entry always has an associated Pending Answer Timer. The Default Pending Answer Timer is assigned to each Application Id if a configured Pending Answer Timer is not assigned.

Diameter selection of the Pending Answer Timer and Transaction Lifetime values to be used when routing Requests upstream will operate as indicated in Table 1.

Diameter Pending Answer Timer and Transaction Lifetime Selection
Routing Option Set specified in Ingress Peer Node?	Pending Answer Timer specified in Ingress Peer Node Routing Option Set?	Egress Pending Answer Timer specified in Egress Peer Node?	Application-ID entry exists for Appl-ID in Request being processed?	Resultant Pending Answer Timer value used Resultant Transaction Lifetime value used (if re-routing is enabled in the Routing Option Set - Maximum Forward Routing Attempts value is greater than 1)
Yes	Yes	N/A	N/A	Pending Answer Timer in Ingress Peer Node Routing Option Set Transaction Lifetime in Ingress Peer Node Routing Option Set
Yes	No	Yes	N/A	Egress Pending Answer Timer in Egress Peer Node Transaction Lifetime in Ingress Peer Node Routing Option Set
Yes	No	No	Yes	Pending Answer Timer in Application-ID table entry for Request's Appl-ID Transaction Lifetime in Ingress Peer Node Routing Option Set
Yes	No	No	No	System Default Pending Answer Timer Transaction Lifetime in Ingress Peer Node Routing Option Set
No	N/A	Yes	Yes	Egress Pending Answer Timer in Egress Peer Node Transaction Lifetime in Routing Option Set associated with configured Application-ID entry for Request's Appl-ID
No	N/A	Yes	No	Egress Pending Answer Timer in Egress Peer Node Transaction Lifetime in system Default Routing Option Set
No	N/A	No	Yes	Pending Answer Timer in Application-ID table entry for Request's Appl-ID Transaction Lifetime in Routing Option Set associated with Application-ID entry for Request's Appl-ID
No	N/A	No	No	System Default Pending Answer Timer Transaction Lifetime in system Default Routing Option Set

The Diameter > Configuration > Pending Answer Timers

On the Diameter > Configuration > Pending Answer Timers page, you can perform the following actions:

Filter the list of Pending Answer Timers to display only the desired Pending Answer Timers.
Sort the list by a column in ascending or descending order, by clicking the column heading. The default order is by Pending Answer Timer Name in ascending ASCII order.
Click Insert.

The Diameter > Configuration > Pending Answer Timers [Insert] page appears. You can add a new Pending Answer Timer.
The Diameter > Configuration > Pending Answer Timers [Insert] page will not open if
- The maximum number of Pending Answer Timers (8) already exists in the system.
Select a Pending Answer Timer in the list, and click Edit.

The Diameter > Configuration > Pending Answer Timers [Edit] page appears. You can edit the selected Pending Answer Timer.

If the selected Pending Answer Timer has been deleted by another user, the Diameter > Configuration > Pending Answer Timers [Edit] page will not open.
Select a Pending Answer Timer in the list, and click Delete. You can delete the selected Pending Answer Timer. You cannot delete the Default Pending Answer Timer.