[SIPForum-discussion] [Sip] What's the difference between session and dialog in SIP?

[gaurav katiyar]

Sip "Session Initiation Protocol". It talks about media session, i mean how to initiate, modify and terminate a session and Dialog provides a sort of context (like caller, callee, location, routing etc.) to modify this session. So dialog is more related to route the sip message to right node and body (SDP) handles media session if present. Dialogs may have media sessions Or may not. 
   
  Take an example of B2BUA. It is a type of statefull proxy having two dialog and one media session if doing media routing. 
  

Donald Lee <baolovebao at gmail.com> wrote:
  old good questions in sip, also add another "transaction".


  On Fri, Apr 25, 2008 at 8:18 AM, å&shy;™å®—君 <szj087 at gmail.com> wrote:
  Hi, Vijay

Thanks very much for your timely answers.

>From this specification,  session is a combination of signaling plane
and media plane messages and processes that enable two or more
participants to communicate. I think session is a larger scope than
dialog. In another word, one session can contain more than one dialog.
Is what I understand right?

Zongjun


2008/4/24, Vijay K. Gurbani <vkg at alcatel-lucent.com>:
    
  > There is some work progressing in the BMWG WG to create performance
>  metrics around SIP.  One of the first tasks in such an endeavor
>  is to define the notion of dialogs and sessions.  Please see
>  Section 3.1.1 of
> https://svn.resiprocate.org/rep/ietf-drafts/gurbani/bmwg-sip-bench-term/draft-ietf-bmwg-sip-term-00.txt
>  of the above draft for some insight.
>
>  Ëï×Ú¾ý wrote:
>
> > Hi, Lincoln
> >
> > thanks for your instructions.
> >
> > I know that dialog can exist without session since SUBSCRIBE/REFER can
> > create dialog and without any media between communication peers.
> >
> > What I want to know is the relationship of dialog and session when
> > they both exist in one communication activity. Take a example, when
> > there are 2 person participating talks with voice, we say there is a
> > dialog and a session.
> >
> > But when one caller invites another callee and gets five 200 final
> > responses from 5 UA every of which has its own session description. We
> > can say that there are 5 dialogs between caller and the other 5
> > callees, right? And then what is the exact number of session in this
> > scenario? One session or five session? That is what I want to know.
> >
> > Dialog is determined by dialogID (call-id, from/to tag) and session id
> > is determined by session id given in the SDP message.  My answer is
> > there are 5 dialog and one session now, right?
> >
>
>  - vijay
>  --
>  Vijay K. Gurbani, Bell Laboratories, Alcatel-Lucent
>  2701 Lucent Lane, Rm. 9F-546, Lisle, Illinois 60532 (USA)
>  Email: vkg@{alcatel-lucent.com,bell-labs.com,acm.org}
>  WWW:   http://www.alcatel-lucent.com/bell-labs
>
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-- 
BR
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Gaurav Katiyar
  Induslogic india pvt. ltd
  B-34/1 sector 59 NOIDA
  Phone:9818381368
   

       
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