PRACK not being retransmitted?

Asterisk 16.28 (I know it’s ancient). PJSIP

I have come across this situation and wonder what the correct procedure would be. Sorry for my laziness, I hope somebody might have stumbled over the issue and could save me some time from digging into the RFCs to figure out.

Asterisk is sending an Invite, 100rel supported.
Bob replies 180 ringing, Required: 100rel
Asterisk answers: PRACK

  • prack is lost - Asterisk does not receive 200 OK to PRACK.
  • What should happen now? Shouldn’t Asterisk Re-Send PRACK after some time?

Bob does not receive PRACK so repeats 180 Ringing Requred 100rel after a while.

  • This looks like a sensible thing to do. Bob has to assume the 180 ringing was lost.

Asterisk does not repeat PRACK upon receiving subsequent 180 ringing.

  • Call fails!

-Benoît-