A Scalable Peer-to-Peer Presence Directory

Instant Messaging (IM) has emerged as a popular communication service over the Internet. One of the themes of IM systems is to provide a presence directory that carries information on user's presence or absence to his/her friends. In this paper, the authors present new presence directory architecture and give a comparison of existing presence directories. They first introduce the distributed buddy-list search problem. They then present P2Dir, a distributed peer-to-peer presence directory protocol to address this problem. For each newly arriving user, the protocol is used to search for network presence of his/her buddies and also to notify them on his/her presence.