1. The Medusa Proxy A Tool For Exploring User- Perceived Web Performance Mimika Koletsou and Geoffrey M. Voelker University of California, San Diego Proceeding of the Sixth International Workshop on Web Caching and Content Distribution.

2. Outline

3. Introduction There has been extensive work evaluating the impact of Web infrastructure for improving overall Web performance, such as cache, prefeth, and to a limit extent content distribution networks. We have a good understanding of how improvements in Web infrastructure impact all latency, server load, and network utilization. But, we do not know how those improvements affect individual user.

4. There is no convenient mechanism to determine the network performance of individual user because of the difficulty of generalizing conclusions about performance results across a wide range of user environments and network location. Therefore, we develop the medusa proxy for individual user to explore network performance.

5. The medusa proxy The medusa proxy is a non-cache forwarding proxy used in conjunction with a user ’ s browser.

6. Features of medusa proxy Mirroring It can be configured to mirror HTTP requests from multiple incoming sources to multiple destinations in sequentially and parallel. In this paper we mirror request to at most two server. The proxy server and origin server.

7. Features of medusa proxy (cont.) Transformation The medusa can install a filters to transform HTTP request as they are forwarded. In this paper we transform Akamaized URLs to the original URLs that refer to customer origin server.

8. Features of medusa proxy (cont.) Performance measurement As it mirror and transformation, the medusa proxy can record performance information, such as request count and frequency, latency, and bandwidth consumed. In this paper they focus on request count and latency.

9. Features of medusa proxy (cont.) Tracing and replay Validation

10. Experimental results The trace between 8 days Total requests are 4743

11. NLANR cache hierarchy The NLANR cache system consists of a hierarchy of international Squid Web caches. The cache hierarchy reduces network utilization and server load, as well as user- perceived download time. It also can degrade the performance when the cache miss.

12. The configuration in medusa proxy They use medusa to mirror all HTTP requests from web browser to both the NLANR hierarchy and the origin servers and record the response time.

13. NLANR results summary

15. Akamai content distributed network CDN has the potential to significantly improve user-perceived Web performance because they can bring the content close to user and balance the server load.

16. The transformation of HTTP request in medusa proxy Typical Akamai URL Transform to Origin server URL

17. Akamai results summary

19. Overall impact of Akamai servers