Quorums-based Replication of Multimedia Objects in Distributed Systems

Abstract

Abstract Background Multimedia objects like music and movies 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) like frame rate and number of colours. For example, there are a pair of replicas o i and o j of a fully coloured movie object o. Here, a content of a replica o i is changed by adding a subobject but another replica o j is not changed. On the other hand, the colour of the replica o j is changed with monochromatic one but not in the replica o i . This means, the replica o i is newer than the replica o j with respect to the content but is older than o j with respect to QoS. Thus, replicas of a multimedia object are partially ordered in terms of newness of not only content but also QoS parameters. Methods In traditional quorum-based (QB) protocols, 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. Here, the replicas are ordered in vectors of version counters of content and QoS parameters. Every replica in a quorum is not updated for QoS operations to reduce the communication overhead. We evaluate the MQB protocol in terms of communication overhead and show the communication overhead can be reduced in the MQB protocol compared with the traditional QB protocol. Conclusions We discussed the multimedia quorum-based (MQB) protocol to keep replicas of a multimedia object mutually consistent. We evaluated the MQB protocol in terms of the total volume of data transmitted among the replicas. Then, we showed the total amount of data transmitted can be reduced in the MQB protocol compared with the traditional quorum-based (QB) protocol.