[Standards-JIG] XEP-0155: do we need it?

Jean-Louis Seguineau jean-louis.seguineau at laposte.net
Fri Nov 10 07:44:23 UTC 2006

Peter, if effectively the main use case is to allow an XMPP endpoint to
negotiate as message session, then we don't need XEP-0155. 

I still have two following questions, though:

- When we first discuss this topic, you brought up that message session
negotiation could also be interesting for XMPP to "formalize" a conversation
in XMPP. I believe the underlying idea was similar to what is being
discussed under "polite blocking". Does dropping XEP-0155 means also
dropping the generic idea of message session negotiation between two XMPP
entities and move to blocking instead? Or does it mean replacing XEP-0155
with Jingle when negotiating message sessions between two XMPP entities? (I
believe this is what you hint at the end of your post, right?). Or both?

- What would happen to file transfers? There will ultimately be no reason to
keep a separate stream negotiation for file transfer streams and other media
streams either. Obviously the file transfer legacy is larger, and an interim
period of cohabitation will be required. 

I believe if we can bring as many "session" negotiations under the Jingle
umbrella as we can, we would have a much clearer protocol situation.


P.S. We could also re-suggest to the SIMPLE working group using XMPP instead
of MSRP. That would certainly bring them good memories back ;) 

-----Original Message-----
Date: Thu, 09 Nov 2006 14:41:23 -0700
From: Peter Saint-Andre <stpeter at jabber.org>
Subject: [Standards-JIG] XEP-0155: do we need it?
To: standards-jig at jabber.org
Message-ID: <4553A083.6020903 at jabber.org>
Content-Type: text/plain; charset="iso-8859-1"

OK, now that XEP-0155 (Chat Session Negotiation) is in Last Call, I've
come to wonder: do we really need it?

One of the main use cases people have in mind for XEP-0155 is enabling
text chat between XMPP users and SIP users. I would imagine that the
protocol spoken by the SIP endpoint will be MSRP once that's all worked out:


But from the SIP perspective, MSRP is just another out-of-band media
session (a la RTP). Now, in order to negotiate a voice or video session
from an XMPP endpoint to a SIP endpoint, we'll use Jingle. So it seems
odd to use something different (XEP-0155) when negotiating an MSRP
session. For MSRP negotiation we might do something like this in Jingle:

<iq from='romeo at montague.net/orchard'
    to='juliet at capulet.com/balcony'
  <jingle xmlns='http://jabber.org/protocol/jingle'
          initiator='romeo at montague.net/orchard'
    <content name='this-is-some-MSRP-session'>
      <description xmlns='urn:xmpp:jingle:description:textchat'>
      <transport xmlns='urn:xmpp:jingle:transport:xmpp'>
      <transport xmlns='urn:xmpp:jingle:transport:tcp'>

And then off we go to negotiate the session.

Naturally we'd need to define the relevant content description format
(text chat) and perhaps some transport methods (another XMPP endpoint
would choose the xmpp method, a SIP/MSRP endpoint would choose tcp, udp,
or sctp). But at least this way we don't have two different ways of
doing what's the essentially the same thing.



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