Mailing List CGatePro@mail.stalker.com Message #98210
From: Lightology Postmaster <postmaster@lightology.com>
Subject: CallCentric SIP not SIP compliant, Not working with CGP
Date: Mon, 6 Jul 2009 10:59:15 -0500
To: CommuniGate Pro Discussions <CGatePro@mail.stalker.com>
X-Mailer: Microsoft Outlook Express 6.00.2900.5512
In the last couple of weeks I was trying to get CGP working on CallCentric.com SIP trunks and I was unsuccessful.
I got great support from both CGP technical support and CallCentric but unfortunately a SIP protocol bug on CallCentric's side will prevent CGP from starting the PBX auto attendant or voicemail and from hanging up a call if the hang-up happens on the far end of the call.
 
CallCentric was not willing to fix the problem so I will not recommend anyone on the CGP list to waste time trying this provider.
 
I included details of the conversations in hopes that it will help with other SIP providers as I am trying now with VoicePulse and I have a different set of problems but still problems. I will report later when is clear.
 
 
Chris Vlad
 
Attached are the protocol suggestions from CGP Support and then the CallCentric response:
 
HANG-UP Problem:
 
That's a problem in the Callcentric's SIP implementation: they attempt
to change the dialog route-set by adding Record-Route headers to the ACK
request sent in response to 200-INVITE. RFC 3261 warns against this:

12.2 Requests within a Dialog
...
    Requests within a dialog MAY contain Record-Route and Contact header
    fields.  However, these requests do not cause the dialog's route set
    to be modified, although they may modify the remote target URI.
    Specifically, requests that are not target refresh requests do not
    modify the dialog's remote target URI, and requests that are target
    refresh requests do.  For dialogs that have been established with an
    INVITE, the only target refresh request defined is re-INVITE (see
    Section 14).  Other extensions may define different target refresh
    requests for dialogs established in other ways.

       Note that an ACK is NOT a target refresh request.

So, CGPro will send BYE to Callcentric using the route-set collected
during the dialog setup, that is from the INVITE request. So, the BYE
request will be addressed to the Callcentric's Contact URI and sent to
204.11.192.31:5080, not to 204.11.192.23:5070 they try to set using
Record-Route headers in their ACK request.

That's why the BYE request sent from CGPro in this dialog may be never
seen by the proper Callcentric server.
---------------------
 
Auto Atendant and voicemail problem:
 
The problem is that the gateway fails to send the ACK to confirm the
reception of 200-INVITE from the Voicemail application that took call to
the pbx@...  account. That must be some issue on the
Callcentric side, you may want to discuss this with their support.
 
> Hello Dmitry,
> here is the response i got from Call Centric:
>
> "one thing that may cause issues is the 200 OK packet being sent from
> your SIP client, specifically the line "Require: timer".

But the incoming INVITE had the "Supported: timer"?

> Within your
> Communigate application, do you have any options relating to
> session-timers?

It's possible to change the minimal and default values for session
timers (Setting -> Real-Time -> Nodes -> Call Legs -> Session
Expiration:), but there's no way to disable session timers altogether:
as long as the peer advertizes support for the "timer" extension, CGPro
will use it.

> If so, is possible, please try disabling this option,
> and let us know whether or not you are able to receive incoming calls."
>
-------------------------
 
Call Centric response:
 
We have on multiple occasions attempted to get CommuniGatePro to work correctly and unfortunately it simply does not work with our service. Please understand that we have many IPBXes, softphones and devices that do work with our service without any issues from around the world, many of which can be seen on our SIP hardware (http://www.callcentric.com/faq/8/48) and software list (http://www.callcentric.com/faq/8/47). Also note the primary developer of our SIP registration and other servers is and was heavily involved in the SIP RFC. You are more then welcome to use another user agent previously mentioned on our compatibility list.
We have on multiple occasions attempted to get CommuniGatePro to work correctly and unfortunately it simply does not work with our service. Please understand that we have many IPBXes, softphones and devices that do work with our service without any issues from around the world, many of which can be seen on our SIP hardware (http://www.callcentric.com/faq/8/48) and software list (http://www.callcentric.com/faq/8/47). Also note the primary developer of our SIP registration and other servers is and was heavily involved in the SIP RFC. You are more then welcome to use another user agent previously mentioned on our compatibility list.

 
 
 
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