Multimedia Quorum-based Synchronization Protocols

Replicas of multimedia objects are distributed to peers in overlay networks. Multimedia objects are characterized in terms of not only data structure parameter but also quality of service (QoS) parameters like frame rate. Replicas have to be synchronized to be mutually consistent. Each parameter of a replica is read and written by transactions. Thus, the data structure and QoS parameters of a replica are manipulated. There are enriching and impoverishing types of write operations. Some data is added to a replica in an enriching operation and is removed in an impoverishing operation. In the MQB protocol, the physical state of each replica is not always updated. If a transaction issues an enriching operation, every replica in the quorum is updated in the same way as the QB protocol. On the other hand, if an impoverishing write operation is issued, every replica is not updated in the quorum. In order to reduce the processing overhead of each replica, we discuss an extended MQB (EMQB) protocol where every replica is not updated even in an enriching write operation. The EMQB protocol is evaluated in terms of the processing overhead of replicas. We show that the processing overhead of each replica can be reduced in the MQB protocol.