Subject: RE: [Sip] bis draft: Minor NIT on Supported header

From: "Drage, Keith (Keith)" <[email-masked]>
Date: Fri, 28 Sep 2001 15:06:23 +0100

Note that this is only for 100 Trying.

My take on the Server and Timestamp headers was that they contain
information that needs to go from UAS to UAC, and which is irrelevant to
intervening proxies. 

As soon as I put a stateful proxy in the way, the information gets lost,
therefore there was no point in including it in the first place.

If I have no stateful proxy in the way, I am left wondering why I was using
100 Trying as a provisional response in the first place, rather than a more
appropriate provisional response (183 Session progress as the end user has
been reached) or even a final response.

Additionally 11.1.1 says "Some unspecified action is being taken on behalf
of this call (e.g., a database is being consulted), but the user has not yet
been located." so I am left wondering whether a UAS can ever generate a 100
Trying provisional response. My current conclusion is no it cannot. This
could be made clearer in the text (i.e. a UAC MUST NOT)

Therefore for the Supported header I am apparently left with requirement for
the proxy to include it in a generated response, without having the
information to include in the first place. 

Your response does tell me that the some change should also be made to the
Timestamp header text in 10.42 in order to exclude 100 Trying provisional
responses. Currently I would read this to require intervening proxies
generating the 100 Trying response to reflect any Timestamp header in the
response. Current text as follows:

"The value of the timestamp is of significance only to the client and it MAY
use any timescale. The server MUST echo the exact same value in all
provisional and final responses and MAY, if it has accurate information
about this, add a floating point number indicating the number of seconds
that have elapsed since it has received the request. "

Only a UAC can generate the server response.

Keith

Keith Drage
Lucent Technologies
Tel: +44 1793 776249
Email: [email-masked]

> ----------
> From: 	Vijay Gurbani[SMTP:[email-masked]]
> Sent: 	28 September 2001 14:41
> To: 	Drage, Keith (Keith)
> Cc: 	[email-masked]'
> Subject: 	Re: [Sip] bis draft: Minor NIT on Supported header
> 
> "Drage, Keith (Keith)" wrote:
> [...]
> > Does anybody see any purpose for any headers other than From; To;
> Call-ID;
> > CSeq; Via; and Content-Length within a 100 Trying response.
> 
> Yeah. Two headers: Server and Timestamp.
> 
> Server identifies the UAS (or proxy) and if the UAC included a Timestamp,
> the UAS should probably echo it (I think the bis has a MUST on this).
> 
> Regards,
> 
> - vijay
> -- 
> Vijay K. Gurbani  vkg@{lucent.com,research.bell-labs.com,acm.org}
> Internet Software and eServices Group 
> Lucent Technologies/Bell Labs Innovations, 2000 Lucent Lane, Rm 6G-440
> Naperville, Illinois 60566     Voice: +1 630 224 0216   Fax: +1 630 713
> 0184
> 

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