Iñaki Baz Castillo wrote:
> Hi, imagine A calls B via proxy P:
>
> - A sends the INVITE to P.
> - P forwards to B.
> - B replies a 200 OK that arrives to P (this would cause proxy core to
> terminate the client transaction).
> - Before A receives the 200 OK it sends a CANCEL to P.
>
> What should do P now with the CANCEL? Note that there is not now an INVITE
> transaction alive for that CANCEL since 200 destroyed it. Maybe P should
> route the CANCEL using the same mechanism used for the INVITE, but surely no
> stateful proxy implements it since it's innecesary in 90% of cases (the proxy
> has already info about the destination for a incoming CANCEL since it
> forwarded before the INVITE).
I don't understand the issue. There is nothing to cancel. The proxy just
sends a 200 to the CANCEL back to A, but doesn't send one on to B. And
of course it forwards the 200 response from B back to A.
This is something like what happens with a forking proxy. The proxy in
general will have some targets it has tried and failed, some that
haven't been tried yet, and some that are in progress. When it gets a
CANCEL, it only sends CANCELs on to the requests in progress, not the
others.
Thanks,
Paul
> Thanks a lot.
>
>
> PD: It's happening to me now in a real environment.
>
>
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