Subject: New (?) idea SUB/NOT, seperate the cases

From: Bernie Hoeneisen <[email-masked]>
Date: Sat, 4 Sep 1999 15:53:58 +0300 (EET DST)

Out of this discussion, there comes some idea into my mind.
It goes somehow backwards, closer to that, what is already stated in the
current draft.
As far as I understood, the main problem is, as long as different 
Call-IDs are used, there isn't any ambiguous BYE command, but 
on the other hand, using the same Call-Id has some advantages in easyness,
less overhead, less resources needed.

So my proposual is, to basically to make two different cases for
subscriptions, with different properties:

- EASY CASE
As far as only the easy monitoring is needed (i.e. no 3rd party
subscriptions, ... ), the same call-ID can be reused in SUB SCRIBE. In
this case a BYE closes ALL sessions related to the call-leg (montoring AND
call sessions). If only the monitoring session is to be closed, Expires:0
is used. (As it has been proposed in this mailing-list earlier)
If this EASY CASE is used, the possible features are restricted
(no 3rd party subscriptions, subscription can't last longer than BYE,
informing of the User Agent about not sending any more NOTIFY is optional
and indicated in a (last) NOTIFY message, ...)

- ENHANCED CASE
If more complicated features are used (3rd party subscriptions, ...),  
the SDP way is used to identify the call and different call-ID MUST be 
used. To terminate the sessions, BYE  SHOULD be used. (If SUB SCRIBE   
Expires:0 is sent, the Gtw sends a BYE to the User Agent, which MUST be
confirmed.)
In this ENHANCED CASE a BYE terminates ONLY the session assigned to the
Call leg.
Further idea: Support of ENHANCED CASE is optional, to allow,
              light weight implementations for SUB/NOT.

Does this sound reasonable? Or does this not solve the problems at all?

t. Bernie

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