[Serusers] Forking Proxy
Klaus Darilion
klaus.mailinglists at pernau.at
Thu Apr 1 09:44:17 CEST 2004
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 at sip.com and user 7000 at 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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>
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