[SIPForum-discussion] what is the diffrence b/w a transaction, session , dialog

XIAO Xiaohong Xiaohong.Xiao at alcatel-sbell.com.cn
Mon Jun 8 01:50:14 UTC 2009

In following diagram, ACK is the 3rd transaction.


From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Samir Patni
Sent: 2009年6月6日 15:48
To: VG; discussion at sipforum.org
Subject: Re: [SIPForum-discussion] what is the diffrence b/w a transaction, session , dialog

Hi Vikas,
Distinction between the three terms is as follows. 
SIP Transaction 
A SIP transaction occurs between a client and a server and comprises all messages from the first request sent from the client to the server up to a final (non-1xx) response sent from the server to the client. If the request is INVITE and the final response is a non-2xx, the transaction also includes an ACK to the response. The ACK for a 2xx response to an INVITE request is a separate transaction
Transaction identified by branch tag of Via field. 
A dialog is a peer-to-peer SIP relationship between two UAs that persists for some time. A dialog is established by SIP messages, such as a 2xx response to an INVITE request. A dialog is identified by a call identifier, local tag, and a remote tag. A dialog was formerly known as a call leg in RFC 2543.
Dialog identified by Call id, To tag and From tag. 
>From the SDP specification: "A multimedia session is a set of multimedia senders and receivers and the data streams flowing from senders to receivers. A multimedia conference is an example of a multimedia session." (RFC 2327 (A session as defined for SDP can comprise one or more RTP sessions.) As defined, a callee can be INVITEd several times, by different calls, to the same session. If SDP is used, a session is defined by the concatenation of the SDP user name, session id, network type, address type, and address elements in the origin field.
Hope this helps 
Thanks and Regards, 
Samir Patni
-----Original Message-----
From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of VG
Sent: Friday, June 05, 2009 6:40 PM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] what is the diffrence b/w a transaction, session , dialog
I m confused with these three things :
Please specify me with an example.
Thanks & Regards,
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