Maximum Post Dial Delay (PDD) Timer

The Maximum Post Dial Delay (PDD) timer measures the amount of time that passes before a final response is received for a SIP Invite. The timer can be configured between 1 and 30 seconds.  If the timer is not configured a value of 30 seconds will always be used. 

For Termination Vendor Trunk Groups, the purpose of the Max PDD timer is to route advance the call to the next available vendor when the vendor does not provide a final response (2XX - 6XX) before the timer expires. The Max PDD timer starts when the Orchestrator sends the SIP Invite to the vendor. The Max PDD timer stops when a final response (2XX -6XX) is received from the vendor. The Max PDD timer expires when a final response (2XX -6XX) is not received during the configured time. If the timer expires, a cancel message will be sent to the vendor. The Orchestrator will then check if the Termination Customer Trunk Group's Max PDD Timer has expired.  If Termination Customer Trunk Group's Max PDD Timer has expired then a SIP 504 Local PDD Timeout final response will be sent to the customer. If the Termination Customer Trunk Group's Max PDD Timer has not expired then a SIP Invite will be sent to the next vendor selected based on the matched routing rule from the termination route plan. If there are no more vendors to route the call to then a SIP 503 Routes Exhausted message will be sent to the customer. 

For Termination Customer Trunk Groups, the purpose of the Max PDD timer to cancel the call when the the timer expires and the current Termination Vendor Trunk Groups Max PDD timer also expires. The timer starts when a SIP Invite is received on the Termination Customer Trunk Group. The timer only stops when the call is established (i.e. a 200OK received by the vendor). No immediate action is taken when the Termination Customer Trunk Group's Max PDD timer expires.

Note: When  Termination Customer Trunk Group Max PDD timer expires the call will not be canceled until the current Termination Vendor Trunk Group's Max PDD timer also expires.

Note: See  B-Timer for an explanation of how the B-Timer and Max PDD work together.

For Origination Customer Trunk Groups, the Max PDD timer is not used and has no impact on call processing.

For Origination Vendor Trunk Groups the Max PDD timer has no impact on call processing.