A Quorum-Based Synchronization Protocol

Multimedia objects are distributed to peers through downloading and caching in peer-to-peer (P2P) overlay networks. In this paper, we consider multimedia objects which are characterized in terms of not only data structure but also quality of service (QoS). For example, there are a pair of replicas oi and oj of a movie object. Here, a content of a replica oi is changed while not in another replica oj. On the other hand, QoS of the replica oj is changed while not in oi. This means, oi is newer than oj with respect to the content but is older than oj with respect to QoS. Thus, replicas of a multimedia object are partially ordered in terms of newness of content and QoS. In traditional quorum-based (QB) protocols theories, replicas are totally ordered just in terms of newness of content. We discuss a multimedia quorum-based (MQB) protocol to synchronize multiple replicas to make consistent on the basis of the newness-precedent relation of replicas. We evaluate the MQB protocol in terms of communication overheads and show the communication overhead can be reduced in the MQB protocol compared with the traditional QB protocols.