| With the popularity of satellite networks as a means for Internet delivery, the performance of the Transmission Control Protocol (TCP) over satellite links has been well studied. Unfortunately, the protocol has shown problems with channel utilization in such environments, which is a key performance factor for satellite operators. Performance enhancing proxies are one solution to this problem, and have been shown to provide significant improvements in channel utilization. Recent research, however, has been focused on the use of adaptive error correction in satellite networks at the lower layers, resulting in the ratification of the DVB-S2 standard. While adaptive error correction can improve channel utilization when channel conditions are good, it also results in decreases in available user bitrate during noisy periods due to the addition of parity bits. The research performed in this thesis shows that the throughput of a performance enhancing proxy suffers when adaptive error correction is introduced, resulting in up to 20% of the bandwidth being wasted during poor channel conditions. A solution involving the addition of a simple bandwidth estimation scheme to the proxy is studied, and is successful in increasing the average channel utilization in poor conditions to almost 90%. Alternatively, it is shown that the introduction of a secondary TCP flow running in parallel with the performance enhancing proxy traffic can result in near 100% channel utilization when priority queues are introduced at the satellite gateway. Tightly integrating performance enhancing proxies with the satellite gateways that employ adaptive error correction is recommended as the best solution. |
