Web Proxy Acceleration

Numerous studies show that miss ratios at forward proxies 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 4-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.

[1]  Paul Barford,et al.  Changes in Web Client Access Patterns , 1998, The Web Conference.

[2]  Sandy Irani,et al.  Cost-Aware WWW Proxy Caching Algorithms , 1997, USENIX Symposium on Internet Technologies and Systems.

[3]  Duane Wessels,et al.  Cache Digests , 1998, Comput. Networks.

[4]  Eric Levy-Abegnoli,et al.  Design alternatives for scalable Web server accelerators , 2000, 2000 IEEE International Symposium on Performance Analysis of Systems and Software. ISPASS (Cat. No.00EX422).

[5]  Michael J. Feeley,et al.  The Measured Access Characteristics of World-Wide-Web Client Proxy Caches , 1997, USENIX Symposium on Internet Technologies and Systems.

[6]  Eric Levy-Abegnoli,et al.  Design and performance of a Web server accelerator , 1999, IEEE INFOCOM '99. Conference on Computer Communications. Proceedings. Eighteenth Annual Joint Conference of the IEEE Computer and Communications Societies. The Future is Now (Cat. No.99CH36320).

[7]  Azer Bestavros,et al.  Distributed packet rewriting and its application to scalable server architectures , 1998, Proceedings Sixth International Conference on Network Protocols (Cat. No.98TB100256).

[8]  Michael RabinovichAT,et al.  A Taste of Crispy Squid , 1998 .

[9]  Anja Feldmann,et al.  Performance of Web proxy caching in heterogeneous bandwidth environments , 1999, IEEE INFOCOM '99. Conference on Computer Communications. Proceedings. Eighteenth Annual Joint Conference of the IEEE Computer and Communications Societies. The Future is Now (Cat. No.99CH36320).

[10]  Burton H. Bloom,et al.  Space/time trade-offs in hash coding with allowable errors , 1970, CACM.

[11]  G. Voelker,et al.  On the scale and performance of cooperative Web proxy caching , 2000, OPSR.

[12]  Willy Zwaenepoel,et al.  Scalable Content-aware Request Distribution in Cluster-based Network Servers , 2000, USENIX ATC, General Track.

[13]  H BloomBurton.  Space/time trade-offs in hash coding with allowable errors , 1970 .

[14]  Azer Bestavros,et al.  Changes in Web client access patterns: Characteristics and caching implications , 1999, World Wide Web.

[15]  Eric A. Brewer,et al.  System Design Issues for Internet Middleware Services: Deductions from a Large Client Trace , 1997, USENIX Symposium on Internet Technologies and Systems.

[16]  Abdelsalam ‘Solom’ Heddaya.  DynaCache : Weaving Caching into the Internet , 1998 .

[17]  Li Fan,et al.  Summary cache: a scalable wide-area web cache sharing protocol , 2000, TNET.

[18]  Erich M. Nahum,et al.  Locality-aware request distribution in cluster-based network servers , 1998, ASPLOS VIII.

[19]  Alex Rousskov,et al.  A performance study of the Squid proxy on HTTP/1.0 , 2004, World Wide Web.

[20]  Duane Wessels,et al.  High‐performance benchmarking with Web Polygraph , 2004, Softw. Pract. Exp..

[21]  Michael Dahlin,et al.  Design considerations for distributed caching on the Internet , 1999, Proceedings. 19th IEEE International Conference on Distributed Computing Systems (Cat. No.99CB37003).