Domain Caching: Building Web Services for Live Events

Web servers providing live coverage of events are hard to design due to a high degree of variation in the load, variation in geographical distribution of users and the frequency with which content is updated. In this paper, we propose domain caching, a technique that dynamically distributes the load on the server by instructing selected clients (domain caches) to cache server content and service requests from nearby clients. We evaluate domain caching using a trace driven simulation study of the 1998 Worldcup Soccer logs. Our simulations indicate that domain caching reduces load on the server by as much as 38% while using a few hundred kilobytes of storage at domain caches. The traces also reveal situations where using domain caching instead of content mirroring reduces network traac from the server. We built a prototype domain cache to demonstrate the feasibility of some of our ideas. Using this prototype, we show that accessing content from a nearby domain cache is faster than accessing the same content from the origin server. Using our simulator to estimate the load on a domain cache, we nd that our prototype is able to handle the load expected to be handled by most domain caches. Accessing the prototype from several clients located geographically near the domain cache suggests that geographical proximity could be used to identify nearby clients.