Subject: [Simple] Sessions of MESSAGEs

From: "Peterson, Jon" <[email-masked]>
Date: Mon, 20 Aug 2001 09:47:55 -0500

After the SIMPLE session last week in London, the SIMPLE chairs received
some feedback from the IESG with regards to the use of the MESSAGE method
end-to-end when an IM session has been established with an INVITE (as
described in draft-ietf-simple-im-session-00).

The IESG has some concerns that this mechanism constitutes the use of SIP as
a transport protocol. In other words, once the session has been established
between the two endpoints by the INVITE, if the MESSAGEs can only go
directly end-to-end, then their headers and related protocol apparatus are
entirely superfluous and may do more harm than good. We saw during the
meeting last week that there were definitely some pitfalls to allowing
methods other than MESSAGE across the IM stream (as well as questions about
overlapping transactions, redirection, forking, and so forth), and it isn't
clear that the overhead is justified if MESSAGE is just an envelope for its
encapsulated MIME payload. The IESG was particularly concerned, in addition
to the protocol overhead, with congestion characteristics of the messaging
session and with the precedent that could be set by using SIP in this
fashion.

For these reasons, the IESG is not inclined to look favorably on that
direction for our protocol work. They also weren't enthusiastic about the
potential use of RTP text for message transmission (significant concerns
were also raised on the floor in London about message framing, especially at
CPIM gateways). The recommendation we've been given is to focus on a
standard transport protocol with understood congestion properties such as
TCP or SCTP. In London, Ben Campbell took an action item to begin
investigating alternatives along these lines given the significant concerns
that arose on the floor with regards to the other approaches. It seems that
the primary question about this approach is what runs over the transport
protocol in question; i.e. MIME headers and bodies, pure message/cpim, BEEP,
plain text, etc.

If anyone feels strongly that we should continue to pursue the use of the
MESSAGE method for direct end-to-end IM signaling, or has input about how
the transport should operate, let's get this discussion underway promptly so
we can meet our projected September deliverables.

Jon Peterson
NeuStar, Inc
SIMPLE co-chair

---

From: Ben Campbell <[email-masked]>
Date: Mon, 20 Aug 2001 09:56:57 -0500

I assume we would still keep MESSAGE for non-session messaging. After 
writing the draft on using MESSAGE in sessions, I am probably its 
biggest critic. I think we should abandon that effort completely.

As far as the message stream itself, I have heard some support for the 
idea of doing pure message/cpim over TCP and TLS. Personally, this 
sounds better the more I think about it.

Peterson, Jon wrote:

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