Quorums for Replication of Multimedia Objects in P2P Overlay Networks

Replicas of multimedia objects are distributed to peers through downloading and caching in peer-to-peer(P2P) overlay networks. Every replica has to be consistent. In quorum-based (QB) protocols, every replica may not be up-to-date and the up-to-date replicas can be found in the version counters. On the other hand, multimedia objects are characterized in terms of not only data structure parameter but also quality of service (QoS) parameters like frame rates. Replicas of a multimedia object are partially ordered in terms of the newness precedent relation on data structure and QoS. Each parameter of a replica is manipulated in read and write operations. In addition, there is a read operation to read a whole replica. A parameter of an object is changed through a write operation. There are enriching and impoverishing types of write operations. Some data is added to a replica in an enriching operation. On the other hand, some data in a replica is removed in an impoverishing operation. In order to reduce the overhead to write every replica in a quorum, we take an approach that every replica is not 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. Impoverishing operations are just recorded in replicas. Then, impoverishing operations are later performed on a replica. The MQB protocol is evaluated in terms of the processing overhead in replicas.0