Mercury

Bimodal Multicast is a protocol developed by Cornell University Computer Science Professor Ken Birman. The protocol accomplishes its multicasting by gossiping information amongst the group members. Bimodal Multicast is also called pbcast, short for probabilistic multicast, because it guarantees with very high probability that either almost all or none of the members will receive a message.

Mercury is a peer to peer chat client with whiteboard that uses Bimodal Multicast as its transport mechanism. You can find out more general information about Bimodal Multicast here , and more technical information here.