RBQ: Congestion-adaptive cooperative caching for the World Wide Web

The topic of this dissertation is the study of coordination strategies between Web caches, with special attention paid to the effects of cross-traffic congestion. Coordination can be in the form of Web caching cooperation or Content Delivery Networks. There are three major contributions made by this dissertation. First, a new coordination scheme, Restricted Broadcast Queries (RBQ), is proposed to address the problems observed in other coordination strategies in the presence of cross-traffic. RBQ's performance is evaluated using analytic and simulation tools, both in the presence and absence of cross-traffic. Secondly, an analytic model is developed that describes the basic behavior of Web cache coordination. Finally, Web cache coordination in the presence of cross-traffic is investigated using trace-driven simulation with the help of real proxy-based traces and synthetic traffic generators. RBQ lowers retrieval times by nearly 50% in the presence of intense cross-traffic congestion (up to 90% reduction in link bandwidth). In the absence of congestion, and for large number of cooperating caches, RBQ yields retrieval latencies 25% lower than other congestion-aware algorithms