Web Proxy Caching: The Devil is in the Details. Ramon Caceres, Fred Douglis, Anja Feldmann, Michael Rabinovich. Proceedings of the Workshop on Internet Server Performance, Madison, WI, June 23 1998.
Abstract
Much work in the analysis of proxy caching has focused on high-level metrics such as hit rates, and has approximated actual reference patterns by ignoring exceptional cases such as connection aborts. Several of these low-level details have a strong impact on performance, particularly in heterogeneous bandwidth environments such as modem pools connected to faster networks. Trace-driven simulation of the modem pool of a large ISP suggests that ``cookies'' dramatically affect the cachability of resources; wasted bandwidth due to aborted connections can more than offset the savings from cached documents; and using a proxy to keep from repeatedly opening new TCP connections can reduce latency more than simply caching data.

Postscript