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USENIX Technical Program - Abstract - Internet Technologies & Systems 99
Scalable Web Caching of Frequently Updated Objects using
Reliable Multicast
Dan Li and David R. Cheriton, Stanford University
Abstract
Frequently updated web
objects reduce the benefit of caching, increase the problem of cache
inconsistency, and aggravate the inefficiency of the conventional "repeated
unicast" delivery model. In this paper, we investigate multicast
invalidation and delivery of popular, frequently updated objects to web cache
proxies. Our protocol, MMO, groups objects into volumes, each of which maps to
one IP multicast group. We show that, by forming volumes of the appropriate
size and/or object correlation, the benefit from reliable multicast outweighs
the cost of delivering extraneous data as well as the overhead of multicast
reliability. Moreover, trace-driven simulations show that the bandwidth saving
over conventional approaches increases significantly as the audience size
grows. We conclude that MMO provides efficient bandwidth utilization and
service scalability, and makes strong web cache consistency for dynamic objects
practical.
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