Subject: [Simple] 'Sessions of MESSAGEs'

From: Oded Cnaan <[email-masked]>
Date: Mon, 27 Aug 2001 11:31:03 +0200

Let's say that user A wishes to send a message to user B, assuming the
session model for messaging. In this case, there are two options:

1. Start a session, send the message and close the session
(INVITE..MESSAGE..BYE) 

2. Start a session, send the message and leave the session open for
consecutive messages. The session will be closed at a later time
(INVITE..MESSAGE..MESSAGE..MESSAGE..BYE)

The first scenario puts a lot of burden on the server (proxy) and network as
it requires several transactions for only sending a single message.

The second scenario, that seems more logical, carries a different kind of
difficulty. In 'All IP' networks, the IP of the handset may be changed by
the network at any time (the user moves to a different base station or even
moves to a different network). When the address of the recipient changes
after a session has already started, consecutive messages will fail.

Unlike VoIP sessions, messages are not streamed so user A has no way to know
that B's address has changed (assuming B is not in A's friend list).

Moving to the more general discussion:

In the discussions so far, it seems that there is a tendency to treat IM as
any other messaging media (VoIP, calls etc.). I understand the 'esthetics'
of this solution but I believe that it neglects the special behavior (and
use) of IM in oppose to other medias.

IM is used in its core for quick, short text messaging while VoIP, a phone
call or even a Quack game are used to create a stream intended to be used
for a long discussion / game / whatever.

It seems to me that SIMPLE should support 2 types of messaging:

1. Direct MESSAGE (as in the current draft) without initiating a session

2. A session based messaging using the second model mentioned above.
(INVITE..MESSAGE..MESSAGE..MESSAGE..BYE) This will be very useful for
initiating chat sessions, in opposed to single messaging.

I would be interested in hearing other people's opinions on that.

Oded Cna'an
VP, New Technologies
Odigo Inc.

---

From: Ben Campbell <[email-masked]>
Date: Mon, 27 Aug 2001 08:56:20 -0500

> it requires several transactions for only sending a single message.

Yes, it does. That is exactly why we are maintaining the use of the 
MESSAGE method for one-shot messages like you describe. Any draft about 
message sessions should (and the one I am working one will) deprecate 
using sessions for single messages to a single endpoint.

> that B's address has changed (assuming B is not in A's friend list).

I don't understand what streaming has to do with noticing your target 
endpoint address has changed, without extra signalling. I assume that a 
message session would allow noticing an network error just as easily as 
an RTP session.

> use) of IM in oppose to other medias.

That is why we are keeping MESSAGE for single, page-model messages.

> initiating chat sessions, in opposed to single messaging.

That was the consensus of the wg meeting in London, and the direction we 
are working on so far.

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