[SIPForum-discussion] To-tag Change
BIENVENIDO A 007MUNDO
joseamartinezp at etb.net.co
Fri Feb 8 19:43:18 UTC 2008
Hi,
Thanks a lot.
When the responses (180 and 200) are sent through a "Proxy" the "UAC" will receive differents "To-tag" for a single request.
UAC--------PROXY-------UA´s things emitted (diferent to tag in 180 and 200)
I understood from RFC that "To-tag", "From-tag" and "Call-Id" must be the same in a dialog (Messages 101-199 included)
Am I wrong?
RFC 3261
[Page 12]
Call-ID contains a globally unique identifier for this call,
generated by the combination of a random string and the softphone's
host name or IP address. The combination of the To tag, From tag,
and Call-ID completely defines a peer-to-peer SIP relationship
between Alice and Bob and is referred to as a dialog.
8.2.6.2 Headers and Tags
[...]
If a request contained a To tag in the request, the To header field
in the response MUST equal that of the request. However, if the To
header field in the request did not contain a tag, the URI in the To
header field in the response MUST equal the URI in the To header
field; additionally, the UAS MUST add a tag to the To header field in
the response (with the exception of the 100 (Trying) response, in
which a tag MAY be present). This serves to identify the UAS that is
responding, possibly resulting in a component of a dialog ID. The
same tag MUST be used for all responses to that request, both final
and provisional (again excepting the 100 (Trying)). Procedures for
the generation of tags are defined in Section 19.3.
12.1 Creation of a Dialog
Dialogs are created through the generation of non-failure responses
to requests with specific methods. Within this specification, only
2xx and 101-199 responses with a To tag, where the request was
INVITE, will establish a dialog. A dialog established by a non-final
response to a request is in the "early" state and it is called an
early dialog. Extensions MAY define other means for creating
dialogs. Section 13 gives more details that are specific to the
INVITE method. Here, we describe the process for creation of dialog
state that is not dependent on the method.
-----Mensaje original-----
De: Robert Sparks [mailto:rjsparks at nostrum.com]
Enviado el: vie 08/02/2008 12:38
Para: BIENVENIDO A 007MUNDO
CC: discussion at sipforum.org; j.martinez at javeriana.edu.co
Asunto: 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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