| Despite widespread interest and technical progress, significant barriers exist for video playback over the Internet. These obstacles include network unreliability, client heterogeneity, and server bottlenecks. Although various play-back systems have been proposed, none address all the issues satisfactorily. This thesis proposes and investigates MiddleMan, an alternate approach.; MiddleMan is a collection of cooperating caching proxies running in a local area network (LAN). Such a configuration offers several advantages. By caching videos relatively close to the clients, MiddleMan reduces overall startup delays and the possibility of adverse Internet conditions disrupting video playback. Additionally, MiddleMan dramatically reduces server load by intercepting a large number of server accesses and can be easily extended to provide other services.; Several issues must be addressed before MiddleMan can be built and deployed. The first problem involves determining the intrinsic properties of video files on the web and how they are accessed over the Internet. Such an understanding is useful in order to effectively detail the architecture of MiddleMan. Hence, I conducted two studies: one to characterize videos on the web and another that analyzes how users access videos. I then used these results to derive the architecture of MiddleMan.; The second hindrance to building MiddleMan involves evaluating and refining the design. Hence, I developed a simulation environment for MiddleMan to test various configurations and caching algorithms. The final design achieves both high cache hit rates and excellent proxy load distribution.; Finally, MiddleMan supports client heterogeneity by converting video to an intermediate format that allows the system to better adjust to client loads. Thus, techniques for fast conversion of video must be developed and integrated into MiddleMan. Hence, I developed a compressed domain transcoder that converts MPEG to JPEG. The transcoder is about 1.5 to 3 times faster than its spatial domain counterpart. |
