Design and Applicability of a Transparent

In this paper we present the design, applicability and preliminary experimental results of the network redirection layer developed at the University of Freiburg as part of Plexor, a load-balancing and fault-tolerance middleware framework. The non-invasive nature of our layer allows all dynamically-linked network applications to beneet from our framework without the need to recompile them, which makes it a very elegant solution to solving some of the problems introduced by design in Internet protocols like HTTP, the Internet Caching Protocol (ICP), and FTP, among others. In the former two protocols, the inability to specify more than one proxy server may lead to decreased performance, or even the report of phantom network failures which could be easily solved by providing an alternate server. In the case of FTP, the inability to specify a set of mirror sites selected at download time based on the current load also leads to a decrease in performance. Rather than trying to nd a solution for each particular protocol in isolation, we have opted to design a general middleware framework that, not only addresses these shortcomings, but also provides additional services, like load-balancing, group membership, etc. without incurring in any noticeable overhead.