Subject: RE: [Enum] Robert and Douglas' Protocols and Services draft...

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 31 Oct 2001 13:14:33 -0500

> -----Original Message-----
> From: Robert H. Walter [mailto:[email-masked]]
> Sent: Wednesday, October 31, 2001 12:46 PM
> To: [email-masked]
> Cc: Michael Mealling
> Subject: QRE: [Enum] Robert and Douglas' Protocols and 
> Services draft...
> 
> 
> Hi Michael,
> 
> Thank you for the feedback... Your suggestion of defining an IANA
> registry for both the protocols and services is excellent and we
> will incorporate this into the next revision of the draft.
> 
> You raise an interesting point regarding the use of SIP with IM.
> Will the SIP extension(s) proposed in the SIMPLE working group I-D
> "SIP Extensions for Instant Messaging" (draft-ietf-simple-im-01.txt)
> be absorbed into SIP or will a new extended SIP protocol (e.g. simple)
> be born?  If the latter is the case, I agree that it makes sense to
> specify SIMPLE as a resolution protocol.

First, let me answer the basic sip questions.

The cited IM draft will not be "absorbed" into SIP in the sense that it is
part of the new baseline specification, currently documented in
draft-ietf-sip-rfc2543bis-05.txt. It is an extension. However, just because
something is an extension to SIP doesn't mean that its a new service, per
se, in the enum sense of service. For example, the SIP extension for caller
preferences (draft-ietf-sip-caller-prefs) is an extension but surely not a
separate service as far as enum is concerned.

Note that there is a slippery slope here, as to what constitutes a new
service, and what does not. IM is a tricky thing. The SIMPLE group is
debating a session model, which would treat IM as a "media stream" alongside
voice and video. The draft you cite above describes the "paging" model,
where you simple send an IM out of the blue. The session model is very
interesting for ENUM. If I want to talk to someone, and I use a SIP INVITE
to set up that call, should there be a separate ENUM service tag for each
different type of media I want to use to communicate with? That is, do we
have E2VOICE and E2VIDEO in addition to E2IM? Interestinly, a call can start
with voice, and later add video. The ENUM resolution would only occur when
the call is initially setup with voice, and not when the video stream is
added. 

The same kind of things can happen for IM. If I set up a call with SIP,
using INVITE, and indicate an IM stream, does that mean that E2IM gets used?
What if the initial call setup has BOTH IM and voice streams? Which service
tag is used? If we don't look at the media streams to determine the service,
and always use E2TEL, say, that means that a page IM could go somewhere
different from a call that has an IM media stream. Is that what we want?

-Jonathan R.

---
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
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From: "Robert H. Walter" <[email-masked]>
Date: Wed, 31 Oct 2001 16:15:19 -0500

Hi Jonathan,

Thanks for the clarification...

> different from a call that has an IM media stream. Is that what we want?

The proposed solution should be flexible enough to allow multiple services
to be associated with a single SIP address, as well as, multiple services
to be associated with multiple SIP addresses.  Consider the following
examples:

1.  A integrated SIP-based IM and voice system on a PC would be specified
    via a single address:
 
    sip+E2IM+E2TEL --> sip:[email-masked]

2.  An IM service is associated with a desktop PC and the voice service
    is associated with an IP-Phone that is managed by a service provider.

    sip+E2IM  --> sip:[email-masked]
    sip+E2TEL --> sip:[email-masked]

How else could the service discovery be accomplished?

Bob
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