[SIPForum-discussion] Difference between DIALOG, SESSION and TRANSACTION

Devanand Kumar devanand at TechMahindra.com
Fri Aug 17 14:02:44 UTC 2007

Hi Lokesh,




Via: SIP/2.0/UDP;branch=z9hG4bK3763983732-38
transaction number


You can see branch- id in the via header that is the transaction

                since sip is a transaction protocol so it required
transaction number to send a request and get response for this




From: sip:+165566611111 at;tag=axes-alc;user=phone

sip:+15053338888 at;tag=alcUA_2242290126-17;user=phone

Call-ID: 11-11-11


A dialog represents a peer to peer SIP relationship between two user
agents which persists for some time.

So a dialog consists call-ID, remote tag and from tag.

Two type of dialog is here:-


Early Dialog:- A dialog established by a non final response.


Confirmed Dialog:- After getting 2xx response.



 INVITE/200/ACK these methods are used to establish a session.


We can say a session has established when INVITE request is getting the
final response 2xx from UAS and UAC send ACK for that final response or
the media negotiation has happened between the UAC and UAS.



Devanand Kumar



From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Lokesh Agrawal
Sent: Friday, August 17, 2007 5:29 PM
Subject: [SIPForum-discussion] Difference between DIALOG,SESSION and


Hi All,

Can Any one tell me difference between DIALOG, SESSION and TRANSACTION.
Please tell in detail with an example.

Thanks and Regards
Lokesh Agrawal


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