Replicating the Contents of a WWW Multimedia Repository to Minimize Download Time

Dynamic replication algorithms aim at allocating, migrating and deleting copies of an object over various Internet hosts, according to the access patterns exhibited online, so as to improve object proximity for the end-users and/ or load-balance the servers. Most of the existing algorithms try to disseminate the objects of an entire Internet Service Provider (ISP), without taking into account the needs and characteristics of specific web sites with large commercial value. In this paper we tackle the replication problem in an Internet environment, inspired by the need of news agencies and other information providers to include in their pages multimedia content without incurring high access delays. We consider an environment that consists of a central multimedia repository and various physically dispersed sites. We propose a cost model to formalize the replication of multimedia objects located at the repository which can result in decreasing the download time. Taking into account implementation issues, such as the storage and processing capacity constraints, the proposed replication policy is evaluated and compared with alternatives including an ideal LRU caching scheme. Qualitative comparisons with the other replication schemes are reported as well.