Parallel-Access for Mirror Sites in the Internet

Popular documents are frequently mirrored on multiple sites in an effort to share the load and reduce clients’ retrieval latencies. However, choosing the best mirror site is a non-trivial task and a bad choice may give poor performance. We propose a scheme in which clients access multiple mirror sites in parallel to speedup document downloads while eliminating the problem of server selection. In our scheme, clients connect to mirror sites using unicast TCP connections and dynamically request different pieces of a document from different sites. The amount of data retrieved from a particular site varies depending on the network path/server conditions. Dynamic parallel-access can be easily implemented in the current Internet and does not require any modifications at the mirror sites. Using dynamic dynamic parallel-access, all clients experience dramatic speedups in downloading documents, and the load is shared among servers without the need for a server selection mechanism. Even in a situation where clients are connected through modem lines, dynamic parallel-access offers transmission rates at least as high as the fastest server.