[Serusers] More call transfer questions

[Evan Borgstrom]

Hey Steve,

	The reason you don't see the REFER is because it wont be sent until
after the re-INVITE is responded to. The idea here is that you are going
to "flash" to a new line or use the Conf/Join buttons on the Cisco
phones which means that the session must be modified before the REFER
can be sent. In your case the re-INVITE will modify the ports and media
parameters in the session and will (usually) move the call from sendrecv
to sendonly state (check the a= tags in the SDP) it will also specify
new parameters in the m= tag in the SDP. The GW needs to respond with a
200 OK before your UA will send a REFER message.

-Evan

On Mon, 2005-02-28 at 16:37 -0500, Steve Blair wrote:
> Thanks. The odd thing is I never see the REFER using ngrep. Any idea why?
> 
> Evan Borgstrom wrote:
> 
> >Hey Steve,
> >
> >	The INVITE's you're seeing are re-INVITES. They're used to modify the
> >session before the Cisco phone sends the REFER to transfer the call.
> >Check out Section 14 of the SIP RFC (3261).
> >
> >http://www.faqs.org/rfcs/rfc3261.html
> >
> >-Evan
> >
> >On Mon, 2005-02-28 at 16:09 -0500, Steve Blair wrote:
> >  
> >
> >>  I'm a bit stuck and wonder if someone on this list can help.
> >>When a call arrives at a Cisco IP phone registered to our
> >>SER proxy from the PSTN it is answered. The called party
> >>then tries to transfer the call. In either case a new invite is
> >>generated. I'm under the impression a refer message should be
> >>generated but given the way attended transfer works on the
> >>7960s it doesn't seem possible to have a refer generated. Has
> >>anyone else seen this? If so any thoughts on what is happening?
> >>
> >>Thanks,Steve
> >>
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> >>
> >
> >
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