Infrastructure-Free Content-Based Publish/Subscribe

Peer-to-peer (P2P) networks can offer benefits to distributed content-based publish/subscribe data dissemination systems. In particular, since a P2P network´s aggregate resources grow as the number of participants increases, scalability can be achieved using no infrastructure other than the participants´ own resources. This paper proposes algorithms for supporting content-based publish/subscribe in which subscriptions can specify a range of interest and publications a range of values. The algorithms are built over a distributed hash table abstraction and are completely decentralized. Load balance is addressed by subscription delegation away from overloaded peers and a bottom-up tree search technique that avoids root hotspots. Furthermore, fault tolerance is achieved with a lightweight replication scheme that quickly detects and recovers from faults. Experimental results support the scalability and fault-tolerance properties of the algorithms: For example, doubling the number of subscriptions does not double internal system messages, and even the simultaneous failure of 20% of the peers in the system requires less than 2 min to fully recover.