Scalable Group Communication Protocols in the Peer-to-Peer Model of Topic-Based Publish/Subscribe Systems

A distributed system is considered in an event-driven model composed of processes which are sequences of events. In this paper, we discuss a peer-to-peer (P2P) model of a topic-based publish/subscribe system (P2PPS model) where each peer process (peer) can both subscribe interesting topics and publish event messages. Since each peer can both publish and receive event messages, a peer may publish an event message e1 after receiving an event message e2. In the P2PPS system, event messages have to be notified to every common target peer in the causal order. In the TBC (topicbased causally delivery) protocol, event messages are causally delivered by taking advantage of physical time in addition to linear time and topic vector. Physical time is used to reduce pairs of event messages unnecessarily ordered. In this paper, we discuss the relation among the clock offset and delay time in the evaluation.