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 uncacheable.

As disk performance continues to lag behind that of memory systems and processors, virtual memory management becomes increasingly important for overall system performance. In this paper we study the page reference behavior of a collection of memory-intensive applications, and propose a new virtual memory page replacement algorithm, SEQ. SEQ detects long sequences of page faults and applies most-recently-used replacement to those sequences. Simulations show that for a large class of applications, SEQ performs close to the optimal replacement algorithm, and significantly better than Least-Recently-Used (LRU). In addition, SEQ performs similarly to LRU for applications that do not exhibit sequential faulting.