[SIPForum-discussion] The process sequence

[Mishra2, Abhishek (NSN - IN/Bangalore)]

Hello
 
 Like to add to Vivek's statement. Usually in IP- IVR /Call agent
scenarios and Tandem cases this is a common scenario. After 183 session
progress, the far end starts the tone.
 
Thanks & Regards
Abhishek 

________________________________

From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of ext Vivek Batra
Sent: Friday, June 19, 2009 12:34 AM
To: 'Mark R Lindsey'; 'Mike Jiang'
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] The process sequence


Number of scnerios exist where 183 Session Progress is sent prior to 180
Ringing.
 
E.g., in VoIP-GSM Gateway, when VoIP end recieves incoming INVITE,
gateway first sends 183 Ringing to alert the caller that call has been
progressed and on reciept of Ringing Alert from GSM network, gateway
sends 180 Ringing to caller which indicates caller that called device is
not ringing. 
 
However, it is upto caller device how to handle the 180 Ringing recieved
after 183 Session Progress.
 
Meanwhile, Linksys ATA provides 'Sticky 183' flag which indicates
whether 180 Ringing should be handled or not if recieved after 183
Session Progress.
 
Best Regards,
Vivek Batra

________________________________

From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Mark R Lindsey
Sent: Friday, June 19, 2009 1:49 AM
To: Mike Jiang
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] The process sequence


Most devices that send both 180 and 183 for one transaction send them
in that order: first 180, then 183. There's no temporal coupling between
180 and 183: they can occur in either order. (AFAIK.)

But beware if you use 183 with SDP, then start streaming RTP to the
calling endpoint, and then send a 180 to the UAC, you may get odd
results (such as overlapped ringback).  


On Jun 18, 2009, at 1:35 PM, Mike Jiang wrote:


	
	Hi All,
	      One quick question: I was wondering if the Ringing (180)
is always occurring ahead of the Session Progress (183).
	      In my case, the 183 response always happened before the
180 happened.
	
	      Thanks,
	
	      Mike J.
	


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