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

[Ramakrishnan R]

This is a wrong interpretation / understanding

ACK will have the same Cseq number as the INVITE

See the detailed messages at
http://www.tech-invite.com/Ti-sip-service-01.html

Regards,
Ramki


On Wed, Jun 22, 2011 at 12:01 PM, Ravikannan Alagarsamy <
ravikannanbe at gmail.com> wrote:

> 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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