[SIPForum-discussion] SIP Sessions and SIP Dialog

Paul Kyzivat pkyzivat at alum.mit.edu
Fri Apr 8 22:07:43 UTC 2016

On 4/3/16 9:44 AM, Jason Morrison wrote:
> Looking for a bit of clarification on the captioned topic. Is it correct
> to say,
> 1)SIP Dialog – Is a completed request with Call-ID, To and From Tags
> established which may or may not consist of a media stream
> 2)SIP Session – Is a SIP dialog that consisting of a media stream.

SIP Session is under defined in a formal sense.

My extrapolation of the intent, using newer terminology is that a SIP 
Session is an INVITE Dialog Usage. (See RFC5057 for discussion of dialog 

The difference is that you can have an INVITE dialog usage that has no 
media. (By doing an O/A with no m-lines, or only m-lines with port=0.) 
This isn't normally very useful, but it might be in some transient 
cases. And I know some that use such with in-dialog MESSAGE. (But this 
latter usage is contrary to SIMPLE policy.)


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