[Nel] Suggestion for the NeL network library / architecture

[Vincent Archer]

According to Jean-Noel Moyne:
> You should have a look at PGM, which is an open reliable multicast
> protocol designed by Cisco and TIBCO (the company I work for), which is
> design to solve just this kind of problems in the most efficient way.

Hmmm, about everyone around started talking about, then dismissing it
as unsuited to our needs, but that's chiefly due to one misunderstanding.

At first we didn't see the "server to server" sentence.

We still don't know how well multicasting can be useful in our server
architecture, because so far, we have very few one-to-many messages
across servers. Most services discuss with a specific target on a specific
service.

However, we still have lots of discussion for the "world service",
i.e. the service which "simulates" the world and run the various objects
and NPC agents. That one might be a candidate for a multicast protocol,
since we can expect replication of objects across multiple world services.

This tie in with another question which I didn't had time to reply to,
regarding how to "split" the world across the multiple world services.
If the split is done by geography (the UO model), then there is little
need of a PGM-based protocol, because most objects will be accessed by
2 world services (edges), or at most 3 (T-intersections). However, if the
split is done instead by reference (i.e. we cluster an agent with the
agents that refer to it more often), then we have a higher redundancy
of agents on servers, and a multicast is probably the best method to
send message to these agents.

-- 
Vincent Archer                                         Email: archer@nevrax.com

Nevrax France.                              Off on the yellow brick road we go!