CACHE COHERENCY IN P2P COOPERATIVE PROXY CACHE SYSTEMS

摘要

Cache coherency plays an important role in the efficiency of a cooperative proxy cache system. In this paper we propose two new cache coherency policies, namely TTL-PI-C and TTL-PI-A to maintain the consistency of cached Web documents in our self-configured, self-managed P2P proxy cache system. Both policies take advantage of flowing Web cache lines among peer proxies that is a vital feature of our P2P proxy cache system. We exercise these policies in conjunction with our Criteria Weighted (CW) cache replacement algorithm and study the cache coherency effects using extensive simulations. We further extend the TTL-PI-A policy into Adaptive TTL-PI that uses the number of replicas known to a certain proxy to dynamically determine the TTL value. The performance study shows that the proposed policies improve the stale access ratios and the average cost bearing (in terms of bandwidth utilization) by commendable margins as compared to the traditional TTL based cache coherency policy.