[SIPForum-discussion] Why Ack is different transaction?

[Robert Sparks]

The destruction of the INVITE transaction on 200 is a known bug in  
the spec and a correction will be published shortly
(if you actually destroy the transaction, you will treat  
retransmissions a new request).

The real reason an ACK-200 is a new transaction is that it must  
follow the route-set established by the 200 to the INVITE.
In other words, it may go to a completely different first-hop  
destination than the INVITE did. Thus, it needs its own transaction
identifier.

RjS

On Mar 28, 2007, at 1:37 AM, Avishek Chowdhury wrote:

> Hi Aditi,
>
> When the UAC receives 200 OK, the client transaction is destroyed  
> at TL.
> This is done because, the TL is unaware of the above core. The  
> above core can be a Proxy or an UAC core.
> In case of proxy, the 200 OK is forwarded whereas in case of UAC,  
> an ACK is generated. Now this ACK has to create a new transaction  
> (transaction created by INVITE had been destroyed)
> at TL for its transmission, hence the ACK for 200 OK is outside the  
> INVITE transaction.
>
> For other non-2xx final responses, the client transaction at TL is  
> not destroyed and the ACK is generated by TL. Hence in this case,  
> the ACK is within the transaction.
>
> Regards,
> Avishek
>
> ----- Original Message -----
> From: aditi g
> To: discussion at sipforum.org
> Sent: Wednesday, March 28, 2007 9:52 AM
> Subject: [SIPForum-discussion] Why Ack is different transaction?
>
> Hi,
>
> I want to know why ACK is considered different transaction from  
> Invite transaction .
>
> regs
>
>
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