Recently, it has been realized that the importance of satisfying service availability is becoming one of the most critical factors for the success of Internet-based services and applications. In this paper, we take an availability-centric view on QoS where the availability is treated as a new controllable QoS parameter and focus on the issues of providing availability guarantees for distributed and replicated multimedia services and contents. We especially tackle the replica placement (RP) problem and study the effects of number and location of replicas on the achieved availability. From a simulation study, we find that (1) the location of replica is a more relevant factor than their number for satisfying the availability QoS requirements for all individual users, and (2) the heuristic methods, in general, cannot give any guarantee for their achieved availability QoS, while they are very efficient for large size graphs.
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