[asterisk-dev] pjsip / asterisk 16: Question regarding 100rel / PRACK

[Michael Maier]

Hello!

I'm *sometimes* facing dropped calls after 900s on outbound calls. I analyzed the traces and could see the following point:

1. Asterisk sends Invite to provider / CSeq 26379 INVITE
2. Provider sends 180 Ringing / require: 100rel RSeq: 2 / CSeq 26379 INVITE

3. Asterisk sends PRACK / CSeq 26380 PRACK / RAck 2 26379
4. Provider sends 200 OK / CSeq 26380 PRACK

5. Provider sends 200 OK / CSeq 26379 INVITE
6. Asterisk sends ACK / CSeq 26379 ACK


900s later

7. Provider sends Update / CSeq 26380 UPDATE
8. Asterisk sends 200 OK / CSeq 26380 UPDATE

9. Provider sends ReInvite / CSeq 26381 INVITE
10. Asterisk sends 200 OK / CSeq 26381 INVITE
11. Provider sends ACK / CSeq 26381 ACK (without any *supported* headers)

12. Provider sends BYE
=> call is unexpectedly ended by the provider.


If it's working as expected, all steps are the same as above, but step 11 contains the supported headers and call proceeds.

Strange: There are two outgoing calls to exactly the same destination. The first call drops after 900s - the second call (restarted directly after the first call has been dropped)
works as expected.


My question (because always if a call was dropped, PRACK has been in use):
Is it a good idea to use a subsequent CSeq for the PRACK on Asterisk side, which is reused later on by the provider for the update (in this example)? Probably it shouldn't harm - but
could this for some devices be nevertheless a problem? For now, I disabled 100rel support on Asterisk trunk side (it was on by default). Let's wait and see what happens ... .


Thanks
Michael