HP Labs Technical Reports

Using Proxies to Enhance TCP Performance over Hybrid Fiber Coaxial Networks

Cohen, Reuven; Ramanathan, Srinivas

HPL-97-81

Keyword(s):Web proxies; TCP performance; Hybrid Fiber Coaxial networks; residential broadband data services

Abstract: Using cable modems that operate at several hundred times the speed of conventional telephone modems, many cable operators are beginning to offer World Wide Web access and other data services to residential subscribers. Initial experiences indicate that real- world Hybrid Fiber Coaxial (HFC) networks are susceptible to a variety of radio-frequency impairments that significantly reduce the benefits of using high-speed cable modems. The effects of packet losses in the access network are particularly accentuated during subscriber accesses to remote servers on the Internet. The longer round trip times in such accesses together with the high packet loss rate result in dramatic degradations in performance perceived by subscribers. This paper shows that by using proxy servers to handle all remote accesses from an HFC access network, the performance of remote accesses can be significantly enhanced even in cases when the proxy servers do not function as data caches. By handling packet losses that occur in the HFC network locally, at low latencies and without the remote server even being aware of the loss, a proxy server enables faster recovery from packet losses. Most importantly, since it controls data transmissions over the local HFC network, the proxy server's TCP implementation can be optimized for the loss characteristics of the HFC access network, enabling a significant increase in performance when the access network is lossy.

21 Pages

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