---------- Forwarded message ----------
From: Xavier Marjou <[EMAIL PROTECTED]>
Date: Jun 1, 2007 3:32 PM
Subject: Re: [Sip-implementors] b2bua Supported: header
To: Ivar <[EMAIL PROTECTED]>


This draft is in an early state and has not received much feedback, so
consider it as an individual work-in-progress (ie: it's far from being
an RFC). Of course, any feedback is very welcome, though I would
prefer to do it on IETF sipping list.

Coming back to your point, the text you have extracted has some
limitations. Let's consider the "100rel" option: it does not make
sense that the B2BUA relay the "100rel" extension if it does not
support the 100rel extension itself (e.g. what is B2BUA does not
support PRACK of RFC3262). Another example is the  "join" extension
received in a request on one side of a B2BUA. The B2BUA can not simply
relay "Require" or "Supported" headers as it needs to be able to
perform a correlation between 2 dialogs as indicated in RFC3911.

I thus think that additional text is needed indicating that the B2BUA
has to understand/implement any extension. If supported, then the
B2BUA can forward the support for this extension, otherwise no.


On 6/1/07, Ivar <[EMAIL PROTECTED]> wrote:
> Hi,
>
> draft-marjou-sipping-b2bua-00
>    If a SIP INVITE message sent by Alice indicates some supported
>   extensions (e.g. 100rel), it is important that the B2BUA forward
>   these extensions in the SIP INVITE message sent to Bob. Otherwise,
>   the two users will never be able to use these SIP extensions.
>
> I can get from there that Supported must be forwarded, isn't it illegal.
> For example UA1 has some xxx feature what B2BUA won't support, now B2BUA
> forwards it to UA2, UA2 requires to handle it but B2BUA don't know how.
>
> I think B2BUA must always generate it's own Supported: with value what
> it supports  or i miss something ?
>
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