[Serusers] AW: Snom phone (fwd) - sr-users

4 Mar 2003

Robert,

the gateway mandates PRACK, that cant be turned off. The OPTIONS can be
avoided if the phone is set to use REFER explicitly.

CS

-----Ursprüngliche Nachricht-----
Von: Robert Messer [mailto:rmesser@abpintl.com] 
Gesendet: Dienstag, 4. März 2003 05:58
An: cs(a)snom.de
Betreff: RE: Snom phone (fwd)

Kevin,

I will try to modify the code accordingly, however, 

I've been looking at the OPTIONS tag.  Perhaps I can tell the
snom phone not to use PRACK?  I'll look into that.

Thanks,

---greg

-----Original Message-----
From: Kevin [mailto:kmoroz@abpintl.com] 
Sent: Monday, March 03, 2003 8:09 PM
To: 'Greg Fausak'
Cc: 'Robert Messer'; sip(a)august.net; serusers(a)lists.iptel.org
Subject: RE: Snom phone (fwd)
Greg, 

   According to snom engineering you should put the routing 
information in the first 200 OK we receive.  Can you do that and try it?

You can test against my proxy if you like to see how it should work. 

Regards, 

Kevin

-----Original Message-----
From: Greg Fausak [mailto:greg@august.net] 
Sent: Monday, March 03, 2003 7:13 PM
To: 'Kevin'
Cc: 'Robert Messer'; sip(a)august.net; serusers(a)lists.iptel.org
Subject: RE: Snom phone (fwd)

Kevin,

I initially sent the packet:

...
  > > This is that packet that came from the last
200 OK <- PROXY:
 > > 
 > > #
 > > U 2003/02/24 07:56:52.503535 216.87.144.203:5060 -> 
 > 216.87.145.22:5060
 > > SIP/2.0 200 OK.
 > > Via: SIP/2.0/UDP 216.87.145.22:5060;branch=z9hG4bK-ng5tokyx448r.
 > > From: "snom man"
<sip:4695461245@augustvoice.net>;tag=8u6ju8wxuc.
 > > To: <sip:2143357976@augustvoice.net;user=phone>;tag=3CBB0360-532.
 > > Date: Mon, 24 Feb 2003 13:56:43 GMT.
 > > Call-ID: 3c267202b6a8-lgseu8olovlp(a)216.87.145.22.
 > > Server: Cisco-SIPGateway/IOS-12.x.
 > > CSeq: 2 INVITE.
 > > Session-Expires: 7200;refresher=uac.
 > > Require: timer.
 > > Allow-Events: telephone-event.
 > > Contact: <sip:92143357976@216.87.144.196:5060;user=phone>.
 > > Record-Route: <sip:2143357976@216.87.144.203;ftag=8u6ju8wxuc;lr>.
 > > Content-Type: application/sdp.
 > > Content-Length: 209.
 > > .
 > > v=0.
 > > o=CiscoSystemsSIP-GW-UserAgent 7543 5694 IN IP4 216.87.144.196.
 > > s=SIP Call.
 > > c=IN IP4 216.87.144.196.
 > > t=0 0.
 > > m=audio 16632 RTP/AVP 0 100.
 > > a=rtpmap:0 PCMU/8000.
 > > a=rtpmap:100 X-NSE/8000.
 > > a=fmtp:100 192-194.
 > >   
This is the 200 OK (response to the INVITE) message as delivered to the
phone.

I couldn't figure out what you were saying, so I went back to
the ethereal trace.  After the snom phone receives a 183 status
message, it sends a PRACK to the PROXY.  This PRACK is
OKed, without a Record-route.  The next message is an OK
responding to the original INVITE, which does indeed have a
Record-Route.

So, you are saying that the OK to your PRACK needs a record route?
I can do that I think, because the OK to the INVITE does indeed have
a Record-route.

I don't even know what a PRACK is for...

---greg

-----Original Message-----
From: Kevin [mailto:kmoroz@abpintl.com] 
Sent: Monday, March 03, 2003 5:19 PM
To: Greg Fausak
Cc: 'Robert Messer'
Subject: FW: Snom phone (fwd)
Hi Greg, 

   Sorry it took so long to get back to you.  Normally it is faster but
as I stated the SIP inter-
operability was last week which caused the delay.  Looks like the issue
is with the 
SER proxy.  If I knew the specification deeper I should have been able
to answer it myself.  Engineering ccs Jiri on their response to me so
he is aware of the issue.  

Regards,

Kevin

-----Original Message-----

The phone updates the route until it receives a 2xx code. The 200 Ok
response does not contain such a route therefore the phone uses the last
route it receives in the 200  which is empty. Therefore, the phone MUST
send the ACK directly to the gateway. 

§ 12.1.2 of the RFC3261. The dialog is NOT established by the
401-challened request.

The proxy can very easily solve the problem by putting itself into the
routing path of the 200 Ok.