A New Survey on Improving TCP Performances over Geostationary Satellite Link

The idea of Internet everywhere makes the assumption that an Internet access should be available even in remote areas without network infrastructure. In this case satellite access represents an attractive solution. Nevertheless, experience shows that over satellite links, TCP is limited in terms of data speeds. Many enhancements and solutions, based for instance on tuning TCP parameters or TCP spoofing, have been proposed to avoid the underutilization of satellite link capacity. These topics have been often addressed, but considering recent high speed TCP variants, the evolution of end users habits, and recently proposed satellite link access scheme, a new study is necessary in order to reconsider some preconceptions and previous recommendations in such a context. This paper proposes an overview of TCP variants and a survey of commonly proposed solutions for TCP over satellite. Then a methodology for TCP performance assessment over satellite links is exposed. The approach is mainly based on a satellite link emulation platform and some tools developed at the ENAC. We assess the gain offered by a split TCP connection with PEPSal comparatively to end to end TCP connections based on NewReno and a recent widely deployed TCP version (TCP Cubic) on an emulated satellite link. Unlike existing studies, we compare PEP advantages with most recent TCP versions and propose as an extension, to assess PEP gain considering the number of simultaneous TCP connections. Finally, the results provided allow us to make some original recommendations toward TCP deployment over satellite links.