Hierarchical Consistency Control for Caching of Dynamic Contents

Abstract

With the help of increasing bandwidth and advanced software technologies, dynamic web pages have been widely applied to various web sites. HTTP/1.1 has provided new control headers for caching the dynamic pages at the proxy efficiently, but it still cannot satisfy all the requirements for dynamic web caching. In this work we present a mechanism to maintain data consistency of various degrees by using active push. We developed an analytic formula for calculation of the update interval Δ given the tolerance value defined by the users depending on the type of object requested. We then designed a hierarchical structure where for each object requested a dissemination tree is created rooted at a leader proxy selected via a hash function. Object updates are pushed from the server to the leader, and further disseminated along the tree only when necessary. We evaluated our design by conducting a trace-based simulation, and the numerical results showed that our analytic formula agreed with the simulation very well. The results also displayed a twenty-eight percent saving in communication bandwidth for the hierarchical tree structure over the flat one.