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Abstract-Much work on the performance of Web proxy caching has focused on high-level metrics such as hit rates, but has ignored low-level details such as "cookies," aborted connections, and persistent connections between clients and proxies as well as between proxies and servers. These details have a strong impact on performance, particularly in heterogeneous bandwidth environments where network speeds between clients and proxies are significantly different than speeds between proxies and servers.We evaluate through detailed simulations the latency and bandwidth effects of Web proxy caching in such environments. We drive our simulations with packet traces from two scenarios: clients connected through slow dialup modems to a commercial ISP, and clients on a fast LAN in an industrial research lab. We present three main results. First, caching persistent connections at the proxy can improve latency much more than simply caching Web data. Second, aborted connections can waste more bandwidth than that saved by caching data. Third, cookies can dramatically reduce hit rates by making many documents effectively uncachable.

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The Domain Name System (DNS) is a critical component of the Internet infrastructure. It allows users to interact with Web sites using human-readable names and provides a foundation for transparent client request distribution among servers in Web platforms, such as content delivery networks. In this paper, we present methodologies for efficiently discovering the complex client-side DNS infrastructure. We further develop measurement techniques for isolating the behavior of the distinct actors in the infrastructure. Using these strategies, we study various aspects of the client-side DNS infrastructure and its behavior with respect to caching, both in aggregate and separately for different actors.