[SIPForum-discussion] transaction...

alexzhang at gdnt.com.cn alexzhang at gdnt.com.cn
Fri Aug 17 07:29:32 UTC 2007

What you said is not the root cause. Please refer to the RFC3261 -17.
      The reason for this separation is rooted in the importance of
      delivering all 200 (OK) responses to an INVITE to the UAC.  To
      deliver them all to the UAC, the UAS alone takes responsibility
      for retransmitting them (see Section, and the UAC alone
      takes responsibility for acknowledging them with ACK (see Section  Since this ACK is retransmitted only by the UAC, it is
      effectively considered its own transaction.
And in my opinion, when the transaction layer of the UAC/UAS will be
destroyed as soon as the 200 OK(Invite) is received. At this time, the
UAC and UAS already know the location of each other. It means that the
stateless proxy between them is not used any more. The ACK, which is
created in a new transaction, will be transmitted from UAC to UAS




From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Donald Lee
Sent: Friday, August 17, 2007 3:05 PM
To: Devanand Kumar
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] transaction...

because it has unique Via branch-ID, which identifying the transaction.

On 8/17/07, Devanand Kumar <devanand at techmahindra.com> wrote: 


	Hi ALL,


	Please tell me the reason that why The ACK for a 2xx response to
an INVITE request is a separate transaction. 


	Thanks and Regards, 

	Devanand Kumar 




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