Re: Definition of the pres: URI in impp-pres-01

Dave Crocker <[email protected]> writes:

> 1. This is supposed to be a minimal system, and that means that the
> argument "I see no reason why we should not add this feature" is
> exactly the wrong criterion. The proper criterion is supposed to be
> "The system will not function without this."

Well, I have ALWAYS argued that the core system has to deal with
"mulicase" fanout.  I suspect that for any presentity there will be
multiple watchers.  If some subset of these watchers are at the same
locations (same "server"), then I maintain that the notification
should be "multicast" from the presentity server to the watcher server
-- one packet over the long-haul link with local fanout.  I've argued
that since 1998, and I still maintain that today.

> 2. Multicast is difficult. One could rather easily argue that
> large-scale protocol infrastructure that relies on serious multi-cast
> -- where there is a logical single entity that is handled as an
> aggregation of sub-entities -- is still a research topic. For example,
> large-scale acknowledgement of multicast packets does not have an
> existence proof, as far as I am aware. Research is not the goal of
> this working group.

I think it very much depends on your definition of multicast.  What I
had in mind was a two-layer "local fanout" tree.  For example, a bunch
of people at MIT are watching someone at CMU.  It would be nice if the
protocol could send a single notification from CMU to MIT and let MIT
fan out the messages to the local users.  Yes, I still say "it would
be nice" because I still don't believe that people understand that
this is a problem.  But I still maintain it is.  I have since 1998. :)

-derek

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       [email protected]                        PGP key available



  [reminder: [email protected] for non-technical discussions, please]