Subject: SUB/NOT - NOT with Exp:0 - RESEND

From: [email-masked] (Lawrence Conroy)
Date: Sat, 4 Sep 1999 18:07:56 +0100

Hi all,
A quick comment on overloading NOT.

I can see only one situation where sending BYE is any kind of a problem for
SUB/NOT - if the "old" INVITE Call Leg has been used in a SUB.

I don't see how it is ever a problem for the Gwy to return a BYE to a SUBber.
Why is this a question? I've been brushed by a bus again.

It seems to me that sending a SUB with Expires:0 to close a monitoring
session is intended to be semantically equivalent to sending a BYE (as it
is described in the PINT draft). It's needed only if one re-uses an
existing (Call-ID, From, To) tuple when opening a monitoring session.

It also seems that a Gwy sending a NOT with Expires:0 is intended to be
semantically equivalent to a Gwy sending a BYE (as described in the Draft).

****
I AM very uncomfortable with using Expires:0 in a NOT for a Gwy to close a
monitoring session. We may wish to keep this for the future, to use where
the contained status information is merely a snapshot (or more generally to
use Expires for status of limited or transient validity).

----------------

Of course, Scott is correct - the Gwy need not send back ANY message,
merely abstaining from sending any more NOTs. Thus sending back a BYE (or
the semantically equivalent NOT with Expires:0) is a MAY, not a MUST.

It IS polite, though, IMHO, particularly if the SUBber is maintaining a lot
of SUBs (as could well be the case for a back-end to a Web Server).

Sorry for the re-sends - I fear something is not quite right with the mail
server, even when avoiding the dreaded S word.

All the best, Lawrence
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| Lawrence Conroy,    | "These Opinions must be mine, 'cos if they    |
| Roke Manor Research |  were my Company's they'd charge you for them"|
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