JGroups Default Protocol Stack UDP Protocol Sends and receives messages on UDP sockets org.jgroups.protocols.UDP Ping Protocol Find the initial membership org.jgroups.protocols.PING Merge Protocol Periodically tries to detect subgroups and emits MERGE events in that case org.jgroups.protocols.MERGE2 Failure Detection Socket Failure detection based on sockets org.jgroups.protocols.FD Verify Suspect Double-checks that a suspected member is really dead org.jgroups.protocols.VERIFY_SUSPECT Stable protocol Distributed message garbage collection protocol. Deletes messages seen by all group members org.jgroups.protocols.pbcast.STABLE Reliable mcast message transission Uses a negative acknowledgement protocol for retransmissions org.jgroups.protocols.pbcast.NAKACK Unicast Protocol Provides lossless transmission of unicast message (similar to TCP) org.jgroups.protocols.UNICAST Fragmentation Protocol Divides up larger message into smaller pieces org.jgroups.protocols.FRAG PB Cast Group Membership Protocol Maintains the member ship view org.jgroups.protocols.pbcast.GMS