NPS: A Non-interfering Deployable Web Prefetching System

4th USENIX Symposium on Internet Technologies and Systems

Ravi Kokku ; Praveen Yalagandula ; Arun Venkataramani ; Mike Dahlin

Others  :  http://www.usenix.org/publications/library/proceedings/usits03/tech/full_papers/kokku/kokku.pdf
PID  :  7059

来源: CEUR

【 摘 要 】

We present NPS, a novel non-intrusive webprefetching system that (1) utilizes only spare re-sources to avoid interference between prefetch anddemand requests at the server as well as in the net-work , and (2) is deployable without any modica-tions to servers, browsers, network or the HTTP pro-tocol. NPS's self-tuning architecture eliminates theneed for traditional \thresholds" or magic numberstypically used to limit interference caused by prefetch-ing, thereby allowing applications to improve benetsand reduce the risk of aggressive prefetching.NPS avoids interference with demand requests bymonitoring the responsiveness of the server and ac-cordingly throttling the prefetch aggressiveness, andby using TCP-Nice, a congestion control protocolsuitable for low priority transfers. NPS avoids theneed to modify existing infrastructure by modifyingHTML pages to include Javascript™ code that is-sues prefetch requests and by wrapping the server in-frastructure with several simple external modules thatrequire no knowledge of or no modications to the in-ternals of existing servers. Our measurements of theprototype under a web trace indicate that NPS is bothnon-interfering and efficient under dierent networkload and server load conditions. For example, in ourexperiments with a loaded server with little spare ca-pacity, we observe that a threshold-based prefetchingscheme causes response times to increase by a factorof 2 due to interference, whereas prefetching usingNPS decreases response times by 25%.