SIP in higher education

[Steve Blair <>]

Jeremy:

 There have been several issues with REFER and call transfer. I was 
looking in Bug Tracker
to remind myself of the details. It seems that the problems I remember 
were in IOS 12.2
releases which we no longer run. However bug #CSCea86574 is a possible 
suspect, at
least for my current problem. In my current case the sip domain name in 
the Refer-To
header has been rewritten to be an SRV name instead of an IP address by 
the time
the REFER message gets back to the gateway.

  The bug report suggests this issue has been fixed however I am not 
running any of the
IOS releases in which the bug has been reported to be corrected. I'll 
come back to this
on Monday when I return.

   Blind and Consultative transfers have been working for us. This is 
the first time in about
eight months that we have experienced an issue. Today all of our phones 
are Cisco phones
however this hasn't always been the case. Call transfer was working in 
the previous
mixed vendor environment.

-Steve
 

Jeremy George wrote:

> Steve,
>
>   Does it make a difference whether the IP devices are all Cisco or
> not?  I _seem_ to recall blind transfers work in all Cisco mode but
> not necessarily otherwise.
>
> - Jeremy
>
>
> On Thu, 24 Nov 2005, Steve Blair wrote:
>
> > Date: Thu, 24 Nov 2005 06:49:12 -0500
> > From: Steve Blair 
> > <>
> > Reply-To: 
> >
> > To: 
> >
> > Subject: Re: [sip.edu] Cisco gateway not handling REFER correctly?
> >
> >
> >
> > Hello Nimal:
> >
> >  I'm out of the office for out holiday however when I return on Monday I
> > will look into this a bit. I think I am having a similar problem. For 
> > me a
> > call comes in from the PSTN via the Cisco gateway to an IP phone. The
> > IP phone blind transfers the call to another IP device and the call 
> > drops.
> > I'll let you know if I discover anything of interest. May I ask that you
> > do the same?
> >
> > Thanks,Steve
> >
> > Nimal Ratnayake wrote:
> >
> > > Apologies for duplicates. previously posted on 
> > > .
> > >
> > > ---------
> > >
> > > Hi,
> > >
> > > When a call between a SIP phone and a PBX extension is transfered
> > > by the SIP phone to another SIP phone, the SIP gateway does not
> > > seem to handle the REFER correctly.  I am using a Cisco 3640 router
> > > running IOS 12.3(12).  The call flow is as shown below ( I have
> > > omitted the proxy in this picture)
> > >
> > >
> > > SIP                             PBX-GW
> > > IP=A.B.C.D                      IP=P.Q.R.S
> > > 1602                            3423
> > >
> > > -------------INVITE--------------->
> > > <------------TRYING----------------
> > > <------SESSION PROGRESS------------
> > > <--------------OK------------------
> > > --------------ACK----------------->
> > > ----INVITE c=IN IP4 0.0.0.0------->
> > > <-----OK c=IN IP4 P.Q.R.S----------
> > > --------------ACK----------------->
> > > -------REFER Refer-To: 1600------->
> > > <-----------Accepted---------------
> > > <------------NOTIFY OK-------------
> > > -------------- OK----------------->
> > >
> > >
> > > Shouldn't the gateway do an invite to 1600 after receiving REFER
> > > *before* sending NOTIFY?
> > >
> > > Any help or pointers to solve the problem would be appreciated.
> > >
> > > Thanks.
> > >
> > > Nimal Ratnayake