There is a new version of the ReplicaNet Freeware SDK available from: http://www.replicanet.com/. ReplicaNet is a multiplayer networking library designed to eliminate the need for specific networking knowledge. Using Replica Object technology enables the programmers of multiplayer games to concentrate on writing a good game.
Features included with version 3.9 include two areas of functionality specifically for Massively Multiplayer Online (MMO) games so that network bandwidth can be redirected to specific machines. These new features incorporate object message reflection and distance based object propagation.