JBoss AS comes out of the box with clustering support. There is no all-in-one library that deals with clustering, but rather a set of libraries, which cover different kind of aspects.
The following diagram shows the basic clustering architecture adopted by JBoss AS 7:
The backbone of JBoss clustering is the JGroups library, which provides the communication between members of the cluster using a multicast transmission.
Multicast is a protocol where data is transmitted simultaneously to a group of hosts that have joined the appropriate multicast group. You can think about multicast as a radio or television streaming ...