Subject: Re: PSTN Interworking Draft

From: [email-masked] (Igor Faynberg)
Date: Wed, 30 Jun 1999 13:49:00 -0400

Adam Roach wrote: 

>As I understand it, the PINT group is using the SUBSCRIBE and NOTIFY
>methods at the suggestion of Henning Schulzrinne. Unless my memory 
>has failed (and I don't claim that it hasn't), he and Jonathan
>Rosenberg had already published a draft based on these methods at that
>time. SUBSCRIBE and NOTIFY have always been meant for further extension.
>

This is somewhat inaccurate.  I will site the meeting minutes from Florida:

"Lev's proposal was to augment the
PINT protocol with the feature by which, the PINT Client can request
notification about the queue progress from the PINT Server. He suggested that
the notification mechanism described in the recent mmusic WG draft "SIP for
Presence"  be used. There was a unanimous agreement that this feature was
important.  As far as the particular implementation is concerned,
Jonathan Rosenberg, the co-author of both SIP and the draft in question,
recommended that only the facilities of the latest SIP specification be used.
He explained that the notification mechanism mentioned by Lev was put together
for the Presence Information Protocol proposal, and was not intended to be
part of the "core" SIP. To summarize, Lev's proposal can be implemented with
the "core" SIP and the SUBSCRIBE/NOTIFY extensions that have been defined for
PINT.  Scott Petrack demonstrated that the present SUBSCRIBE/NOTIFY PINT
mechanism, augmented by filtering, is sufficient to support the feature.
There was no disagreement with that solution."

>Nonetheless, have faith that, in the unlikely event that the
>proposed extensions are in conflict with existing work, they will 
>quickly be adjusted so as to not interfere.
>

Perfect. We seem to have no problem then!

>>So, Lawrence and I do belong to this "don't overload" club, and we heartly
>>welcome you to join it!
>
>Unfortunately, you're a bit late in the game to effectively weigh in on
>this topic. SIP's proposed extensions are rife with examples of messages 
>serving multiple purposes, many written by the authors of the original
>draft. This is the primary method currently used for extending the
>protocol. I discovered some time ago that the introduction of new
>method names is met with great resistance (and I have since come to
>believe that there is some justification for this).
>

No, no, I was just kidding about joining the club! (Hence the word "club.") 

>I want to emphasize that I don't necessarily think your concerns are
>unjustified, and I do beleive that they will be addressed by the MMUSIC
>group. 

This is perfect.

>My point is that your proposed solution is contrary to the 
>informal design philosophy that has been established for SIP through 
>existing drafts.
>

The point is well taken.  My recommendation (the word "proposal" is  
misnomor; had I had a proposal, I would have sent it to MMUSIC, not PINT) 
was to demonstrate feasibility of making things backward-compatible by
example. I don't care how it is done actually.

In any case, I really see no big problem, and--with Adam's response--no problem
at all.

Igor

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