[SIPForum-discussion] question on PRACK

[Howell, Tod]

http://www.ietf.org/rfc/rfc3262.txt

http://excelsupport.dialogic.com/imgpubs/webhelp/Description/SIP/sip_prack.htm

I sent these links to someone on this forum last week.  I had this issue with a service provider IVR.  The isdn q931 message was stopping at in "band information available" and from call manager, continued to hear ringing.  The last sip message sent to call manager was provisional response 183.  In this case, it needed to be delivered reliably due to a security feature in IVR.  I had to enable prack in my sip profile in my call manager sip trunk to guarantee reliable response to provisional sip responses.  Above is a link to the ietf, and a nice over view and explanation.

Good luck!!



________________________________
From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Raghul Prasanna
Sent: Wednesday, May 11, 2011 5:58 PM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] question on PRACK

Hello all,

One of our carrier requires support for PRACK.

When the carrier sends 183 Session Progress, we send PRACK and receive 200 OK for the PRACK.

Then they again send 180 Ringing and our SBC rejects the call.

I believe we are right here to reject the call, because the carrier shouldnt be sending 180 ringing after receiving PRACK for 183 Session Progress. Please let me know.

Also if possible please point me to any rfc which says PRACK to 183 should not be followed by 180.

Thanks,
Raghul



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