[SIPForum-discussion] The process sequence

[Mark R Lindsey]

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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