[SR-Users] CANCEL before INVITE

[Klaus Darilion]

Just the theory.

The proxy - if stateful forwarding is used, e.g. by using t_relay() - 
must not forward the CANCEL unless a provisional reply is received from 
the cisco phone.

regards
klaus

Am 17.06.2010 21:49, schrieb David:
> Hey,
>
> I am using a Cisco WIP310 wifi phone. Seeing as wifi is very battery
> demanding, the phone goes into a standby mode. When it's in the standby
> mode, it takes a few seconds to come back on.
>
> So I send an INVITE to the phone, statefully using TM, I send out a
> CANCEL before the phone returns the "180 ringing" message.
>
> Somehow the device is answering the CANCEL before the INVITE, so the
> result is that it responds to the CANCEL with "481 Call Leg/Transaction
> Does Not Exist.", after that it responds to the INVITE with a "180
> Ringing", the phone than rings indefinitely because the CANCEL is not
> sent out again as the transaction is completed from the 481 SIP message.
>
> I had a look at the CANCEL, there is no Route: header or tag on the To,
> so it looks like it is part of a new dialog ( I believe that's what
> rfc3261 says.
>
> As far as I can tell, my Kamailio is working properly. It is
> retransmitting the messages at the proper intervals, and it is passing
> along the messages as it receives them.
>
> The trouble is that the device answers the initial CANCEL before it
> answers any of the retransmitted INVITEs.
>
> Is there something that I can do in Kamailio to resolve this issue ? Is
> there an option that I can set that will cause Kamailio to relay the
> CANCEL only to devices that have already returned a 100 Trying or 180
> Trying ?
>
> What information do you need to know about my config? What parts of the
> SIP trace do you need ?
>
> Thanks,
>
> David
>
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