An admission-control technique for delay reduction in proxy caching

摘要

We evaluate an admission-control (screening) policy for proxy server caching that augments the LRU (Least Recently Used) algorithm. Our results are useful for operating a proxy server deployed by an Internet Service Provider or for an enterprise (forward) proxy server through which employees browse the Internet. The admission-control policy classifies documents as cacheable and non-cacheable based on loading times and then uses LRU to operate the cache. The mathematical analysis of the admission control approach is particularly challenging because it considers the dynamics of the caching policy (LRU) operating at the proxy server. Our results show substantial reduction (around 50% in our numerical simulations) in user delay. The improvement can be even larger at high levels of proxy server capacity or when the user demand patterns are more random. An approximation technique provides near optimal results for large problem sizes demonstrating that our approach can be used in real-world situations. We also show that the traffic downloaded by the proxy server does not change much (as compared to LRU) as a result of screening. A detailed simulation study on LRU and other caching algorithms validate the theoretical results and provide additional insights. Furthermore, we have provided ways to estimate policy parameter values using real-world trace data.