[SIPForum-discussion] To-tag Change

[Manpreet Singh]

In forking scenario, shouldn't the proxy be smart enough to not pass 200 when it has passed 183 from a certain endpoint. Usually in forking, the proxy would CANCEL other requests once it has recieved 18x for one of the requests to get out of this situation. Even when 183 does early dialog, the UAC doesn't expect the tags to change for that dialog. Getting different To tags would cause issues with dialog identification.

M

-----Original Message-----
From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Robert Sparks
Sent: Friday, February 08, 2008 12:38 PM
To: BIENVENIDO A 007MUNDO
Cc: j.martinez at javeriana.edu.co; discussion at sipforum.org
Subject: Re: [SIPForum-discussion] To-tag Change

You can see a 200 with a different to-tag than you saw in the 180 in the real world.
Its not that the thing emitting the responses changed the tags - its that different things emitted the responses.

If the request forked somewhere downstream from you, you could have one branch of the fork return a 180 and the other return a 200, leading to what you're seeing.

RjS

On Feb 8, 2008, at 11:12 AM, BIENVENIDO A 007MUNDO wrote:

> Hi,
>
> Do you think that is possible to change "To-tag" field in a 200ok 
> message after receiving 18X message with to-tag?
>
> The references aren't clear neither RFC3261 nor drafts (for example 
> http://tools.ietf.org/id/draft-ietf-sipping-service-examples-13.txt).
>
> In draft example 2.9 (call forwarding - no answer "sequential 
> forking"), "To-tag" F5 message (180) is different than "To-tag" in
> F13 message (200ok), otherwise in RFC3261 the session is established 
> with unique ID, this ID is composed of "From-tag", "Call-Id" and 
> "To-tag".
>
> My Switch doesn't accept 200ok with different "To-tag" if previously 
> has received a 180 message.
>
> Can someone clarify this issue please?
>
>  Thanks,
>
> José.
>
>
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