[Standards-JIG] SIP functionality and XMPP

Damon Lanphear damonlan at real.com
Tue Mar 16 19:09:22 UTC 2004

I'm just getting caught up on the list discussion of IETF multimedia
protocol convergence under XMPP.  It seems that there is some momentum
to develop an umbrella specification that encapsulates the IETF MMUSIC
suite in a "jabber friendly" protocol framework.  Frankly, I don't
totally grok the scope of the current approach.  Is it that all
functionality of SIP will be inherited by SIP-XML?

If that is the case, then I think this is mistake.  Its already been
mentioned on the list that SIP has industry acceptance and increasingly
broad deployment.  More importantly, is that SIP is sufficiently generic
to create a complex feature set that is difficult to represent cleanly,
and implement correctly.  In other words, a LOT of work of has gone into
SIP.  In this respect, re-inventing the wheel to make SIP concepts play
nice in jabberland is falsely attractive.

I propose that we think first about what sort of high level functional
semantics we want to support.  Then we define a mapping for those
semantics to the *existing* protocol suite. Finally we develop an
"jabber-friendly" protocol spec that articulates this mapping.  The
envisioned deployment is that existing RTSP/SIP/SDP implementations can
be extended to listen for and translate XMPP-media protocol messages to
RTSP/SIP requests and calls.

A model just like this was employed by IETF's MEGACO. MEGACO basically
provides a translation service for driving media gateways on the
boundary between VoIP and conventional telephony networks. Of course,
MEGACO is not of use to us other than as a protocol example of how
existing communications technologies can be bridged to emerging ones.

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