Subject: Re: PSTN Interworking Draft

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

---

From: Igor Faynberg <[email-masked]>
Date: Wed, 30 Jun 1999 12:30:41 -0400

There is going to be a new draft soon, but this will beef up only the security
section. (It is likely to come right after the IETF meeting, with the intention
of going for the last call.) As far as SUBSCRIBE/NOTIFY mechanism is concerned,
it has been much discussed and virtually unchanged for a while.

[For reference: The PINT SUBSCRIBE/NOTIFY mechanism was discussed at the last
PINT meeting (in Florida) at length, and it was agreed that PINT needed those
mechanisms as presented, and that they were not part of SIP specification then.]

So, to follow Henning's call, please take a look at the latest draft 
on the PINT page. Henning is absolutely right in that the discussion of any
topic can be reopened (although, based on the stability of the material a few of
us have proceeded with the implementations...)

Igor

Henning Schulzrinne wrote:
> 
>...It would be useful if people
> take a look at PINT to see if it fits a reasonable, generalizable
> subscription model. If not, PINT should be changed before it's too late.
> 
>