[SIPForum-discussion] Why ACK is separate transaction for INVITE

[Ravikannan Alagarsamy]

Yes I know, Only branch paramaters in Via  will change.

On Thu, Jun 23, 2011 at 1:07 PM, Johnson Jagasetty <johnsetty at hotmail.com>wrote:

>  Hi Ravi,
>
> CSeq  in ACK message must be same as INVITE for successful completion of a
> dialog. CSeq is not incremented.
>
> If for INVITE :
> CSeq: 1 INVITE
>
> for ACK
> CSeq: 1 ACK
>
>
> Regards,
> Johnson
>
> ------------------------------
> Date: Wed, 22 Jun 2011 12:01:45 +0530
> From: ravikannanbe at gmail.com
> To: retesh.chadha at gmail.com
> CC: discussion at sipforum.org
> Subject: Re: [SIPForum-discussion] Why ACK is separate transaction for
> INVITE
>
>
> Hi,
>
> Hope you know that for every new transaction Cseq should increment if it is
> not increment means that should be same transaction(non-successful call).
>
> So as per 3-way handshake policy once it gets 200ok response it sent ACK
> with increment Cseq id and it is separate transaction. if it is not
> incremented means the call is not successful we are sending ACK for some
> error message.
>
> Thanks
> Ravi
>
> On Tue, Jun 21, 2011 at 4:12 PM, Retesh <retesh.chadha at gmail.com> wrote:
>
> Hi
>
> I think 1 of the reason is that ACK for 2xx can take a different network
> path then INVITE or 2xx messages based on the contact and route set received
> in 2xx and so it needs to be a separate transaction (different Via header
> and branch parameters), which is not the case with ACK for non-2xx final
> response.
>
> Hope this helps.
>
> Regards
> Retesh
>
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