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 [EMAIL PROTECTED] and user [EMAIL PROTECTED] 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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