Subject: Re: PSTN Interworking Draft

From: Sean Olson <[email-masked]>
Date: Sat, 26 Jun 1999 12:30:31 -0500 (CDT)

> 
> At 9:44 am 25/6/99, Adam B. Roach wrote to the MMUSIC list:
> >The following draft is now available from the Internet Drafts
> >archive:
> >"SIP PSTN Interworking Umbrella 'Require:' Header"
> >     This document outlines a new value for the SIP "Require:" header
> >     which denotes compliance with a number of mechanisms necessary to
> >     interwork smoothly with existing telephony networks.
> >
> 
> To which I reply:
> I have a slight qualm with this document. The PINT Drafts have had two
> methods called SUBSCRIBE and NOTIFY for a long while now (basically since
> Henning and Jonathon originally suggested them to us when what is now IMPP
> started).
> 
> I HOPE that the SUBSCRIBE/NOTIFY stuff of section 2.4 (with the note "This
> document is not yet written.") isn't going to clash with the existing PINT
> use, otherwise we'll break things (I trust that isn't the intent :). A
> similar approach seems likely in any PIN work, and any revivification of
> the SIP-for-Presence work. Any new document is not going to hit an empty
> table.
> 
> All the best, Lawrence
> -----------------------------------------------------------------------
> | Lawrence Conroy,    | "These Opinions must be mine, 'cos if they    |
> | Roke Manor Research |  were my Company's they'd charge you for them"|
> |- [email-masked]  ---+- Tel: +44 1794 833666  Fax: +44 1794 833434 --|
> 

The intent of the document was not to re-invent anything but to bring the
various drafts concerning PSTN-SIP interworking under one umbrella draft to
simplify the development and standardization of SIP nodes which must 
interwork with the PSTN. Whatever SUBSCRIBE/NOTIFY methods can be agreed upon
and standardized will be used. (Whether from PINT, PIN, IMPP or MMUSIC)

-----------------------------------------------------------------
Sean Olson            E-mail: [email-masked]
Ericsson Inc.         Voice: (972) 583-5472 
                      FAX: (972) 669-0154

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From: [email-masked] (Igor Faynberg)
Date: Wed, 30 Jun 1999 11:29:25 -0400

Adam Roach wrote:

To avoid further confusion, reference to the other two other                    
drafts should be made, with a note that neither are sufficient                  
for the purposes of DTMF information transmission. The 01 version               
of my draft will reflect these changes.                                         

Adam, 

Thank you for your understanding and for quick reaction to Lawrence's
note.  I think you correctly point out that the key-words are overloaded;
I think a solution to that is simply to use keywords that are different
than the ones that have been spoken for already.  The matter of fact is
that SUBSCRIBE/NOTIFY statements that have already been agreed on as
SIP extensions for PINT do have specific semantics, including the sequnces
in which they appear.

If you believe that the same mechanisms can be used elsewhere to do 
something else (i.e., DTMF transmission), you should ensure that whatever
solution you propose is backward compatible. If you believe that the
mechanisms may not be used (which is what I believe you are saying), the
best thing would be to use different names. For example, in the case of
DTMF, it would perhaps be appropriate to use DTMF-SUBSCRIBE, DTMF-NOTIFY.

I reailize that my proposal may be controversial. Ever since Unix shell
was introduced, some people thought it was great to have ONE shell script
with hundreds of parameters covering ALL possible cases. Others argued
that remembering such parameters and--especially--remembering the combinations
of them that correspond to one or another specific usage is impossible and
to learn the usages is very hard. It would much better to have several
different shell procedures, each having its own set of necessary and
sufficient parameters. This makes both the design and use unambigous. If
you change something, you know that the impact of your change is localized.

So, Lawrence and I do belong to this "don't overload" club, and we heartly
welcome you to join it!

Respectfully,

Igor Faynberg

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