[SIPForum-discussion] 180 Ringing with SDP

[Stewart Bunce]

Esentially what you are describing is call forking. In this case, as the 200 OK you receive is from a different device to the 180 with SDP you have already received, it will have a different far end (TO) tag in it. User 1 (Machine 1) should recognise this, send a CANCEL to Machine 2 and accept the response from Machine 3 by sending an ACK. The media settings from the 200 OK from Machine 3 will be used.
 
Stew 

-----Original Message ---
From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org]On Behalf Of Raghul Prasanna
Sent: 07 August 2008 11:29
To: discussion at sipforum.org
Subject: [SIPForum-discussion] 180 Ringing with SDP



Hi,
 
  Say if user 1 is registered to Machine 1 and User 2 is registered to Machine 2 and Machine 3. I call User 2 from User 1.
 
   In wireshark trace I see 180 Ringing with SDP and both the machines to which User 2 is registered rings. But I think we shouldnt be getting 180 with SDP because say if we get 180 Ringing with SDP from Machine 2 and the User Picks the phone on Machine 3 which has different Media settings, the 200 OK will have different SDP and 180 will have different SDP. 
 
  Or shd it be following what RFC 3261 says  
 
"If more than one Contact is sent in a REGISTER request, the
   registering UA intends to associate all of the URIs in these Contact
   header field values with the address-of-record present in the To
   field.  This list can be prioritized with the "q" parameter in the
   Contact header field.  The "q" parameter indicates a relative
   preference for the particular Contact header field value compared to
   other bindings for this address-of-record.  Section 16.6 describes
   how a proxy server uses this preference indication."
 
   So in this case if the User with higher preference doesnt answer, will the proxy will try calling the user with next preference and in this case send a new invite to the other user?
 
Thanks,
Raghul
 

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