Research On Caching Mechanism In Publish/Subscribe Networks

Publish/subscribe system is characterized as an asynchronous, looselycoupled, and multipoint communicating system, and well satisfies theneeds for a higher dynamics and lower degree of coupling in massivedistributed systems. In traditional Pub/Sub system, it is impossible forsubscribers to retrieve messages published before they join, and clientsmay also miss messages in the mobile setting. To solve these problems,caching is needed for publish/subscribe systems to support access forpreviously published messages.In this paper, we propose a hash-based path caching protocol, inwhich messages are cached at the brokers and their neighbors along thedelivery path. As well as a hash function adopted to determine cachelocation, routing information is extended to enable the retrieval of cachedmessages. Additionally, to control the redundancy to a proper degree, twoobjective functions are employed to solve the caching duplication andreplica placement problem, given the network characteristics and historicalinformation of user requesting.Moreover, to cope with the mobility scenario, we propose anotherproactive caching mechanism, selecting for each message a proper cachepoint along its delivery path, so that the mobile user can obtain an efficientcache accessing and network performance across different locations.