Web Proxy Acceleration

Numerous studies show that miss ratios at forward proxy are typically at least 40%-50%.
This paper proposes and evaluates a new approach for improving the throughput of Web
proxy systems by reducing the overhead of handling cache misses. Namely, we propose
to front-end a Web proxy with a high performance node that filters the requests, processing
the misses and forwarding the hits and the new cacheable content to the proxy. Requests
are filtered based on hints of the proxy cache content. This system, called Proxy Accelerator,
achieves significantly better communications performance than a traditional proxy system.
For instance, an accelerator can be built as an embedded system optimized for communication
and HTTP processing, or as a kernel-mode HTTP server. Scalability with the Web proxy
cluster size is achieved by using several accelerators. We use analytical models, trace-based
simulations, and a real implementation to study the benefits and the implementation tradeoffs
of this new approach. Our results show that a single proxy accelerator node in front of a four-node
Web proxy can improve the cost-performance ratio by about 40\%. Hint-based request filter
implementation choices that do not affect the overall hit ratio are available. An implementation of
the hint management module integrated in Web proxy software is presented. Experimental
evaluation of the implementation demonstrates that the associated overheads are very small.