End-to-End TCP Enhancements Performance on Satellite Links

Although TCP has proved very effective and robust for many years, its performance on emerging heterogeneous networks is challenged by the impairments originated by the presence of radio links. In particular, satellite communications are affected by long RTTs and possibly also by random segment losses, which can severely affect end-to-end performance. To cope with these problems, several TCP enhancements have been presented in the literature. The paper aim is to investigate the effectiveness of such modifications, when applied to TCP satellite connections. In particular, the analysis focuses on some emerging proposals, namely TCP Hybla, developed by the authors, and TCP Westwood, examined here in three variants. They are compared with three well established TCP variants, such as NewReno, SACK and Vegas, taking into account both a pure satellite environment and more challenging, but also perhaps closer to reality, heterogeneous network. Performance is assessed by means of ns-2 simulations considering goodput, fairness and friendliness as performance metrics. Results show that large performance improvements may be achieved by some of the considered TCP enhancements, without infringing the end-to-end semantics of this protocol.