PDD (Post Dial Delay) -  is experienced by the originating customer as the time from the sending of the final dialled digit to the point at which they hear ring tone or other in-band information. Where the originating network is required to play an announcement before completing the call then this definition of PDD excludes the duration of such announcements.

For SIP the PDD would be the time from Sending the INVITE to receiving the first ringing response for example: a SIP/2.0 180 Ringing repsonse.