Analysis of TCP live experiments on a real GEO satellite testbed

The paper describes a measurement campaign carried out by the University of Bologna (UoB), the National Inter-University Consortium for Telecommunications (CNIT) and the University of California Los Angeles (UCLA). The aim of the experiments was the performance assessment of a wide range of TCP enhancements on network environments that include a real GEO satellite link. To this end, UoB and CNIT integrated their network tools and set up a testbed composed of a cluster of UoB Linux PCs connected to the CNIT GEO Skyplex satellite platform. Tests were conducted considering both end-to-end TCP enhancements and a TCP-splitting Performance Enhancing Proxy (PEP) developed by UoB. The analysis was not limited to isolated satellite links, but embraced more complex heterogeneous networks, where satellite connections have to compete with wired cross traffic for the network resources. The analysis of the large set of experimental data presented in the paper confirms the challenges posed by GEO satellite channels, which, in this case, were worsened also by the presence of Bandwidth on Demand technique, which impacts TCP performance. Among the end-to-end TCP variants, best results are generally shown by TCP Hybla, especially when heterogeneous environments are considered. On the other hand, the splitting PEP solution offers the best performance with respect to all TCP enhancements, due to its ability to isolate satellite channel impairments. The possible drawback of this approach is in that it violates the end-to-end semantics and is incompatible with IPsec protocol implementation.