UA1 behaves wrong - per RFC 3261 the dialog will be established by the 200 OK message (not by 180), therefore the to-tag from the 200 OK must be used.
It makes no sense to deal with such wrong implementations in the SIP proxy.
Which client is UA1?
Klaus
Jason Penton wrote:
Hi All
I have a question about the CORRECT operation of UA when making a call via a forking proxy:
Lets say UA1 calls 7000@sip.com and user 7000@sip.com is available at UA2 and UA3 i.e. the Proxy forks the request.
UA1 Forking UA2 UA3 Proxxy 1 |------INVITE---------->| | | 2 | |--------INVITE-------------->| | 3 | |---------------------------INVITE------------->| 4 | |<---RINGING(totag=1234)------| | 5 |<---RINGING(totag=1234)| | | 6 | |<------------------RINGING(totag=5768)---------| 7 |<---RINGING(totag=5678)| | | | | | | | | | |
NOW UA3 WILL ANSWER| |<----------------200 OK (totag=5678)-----------| 8 |<-200 OK (totag=5678)--| | | 9 |---ACK (totag=1234)--->| | | 10 | |------------------ACK (totag=1234)------------>|
AT THIS STAGE UA 3 IGNORES THE ACK AS IT DOES NOT CORRESPOND TO ORIGINATING 200 OK AND THE CALL IS NOT SETUP
- UA1 is using the to-tag of the first 180 RINGING it received (frame 5) no
matter what the to-tag in the 200 OK is
- My question here is: who is in the wrong???? The proxy or UA1?
- Should the proxy change the to-tag of the ACK before forewarding it to
UA3???
Any help/guidance would be much appreciated Jason Penton Rhodes University Grahamstown South Africa
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