Investigating TCP performance issues in satellite networks

TCP is the widely used transport protocol across the Internet but it was originally designed for wired networks. In satellite networks, TCP encounters serious problems due to the physical properties of the wireless medium. The high delays in GEO networks and high variability of delay in LEO systems are the most significant factors affecting TCP performance. This paper identifies and illustrates TCP performance issues in satellite links by making a detailed comparison between these two common satellite altitudes. In low altitude satellite constellations, the propagation and switching delays are highly variable because of routing changes and handovers. Previous work on variable delay has focused explicitly on the retransmit timer. This paper makes a flow based analysis of abrupt delay changes to better understand TCP performance in LEO systems. Simulations are performed with the NS 2 satellite extension using the iridium constellation. It is observed that TCP performs better in LEO than in GEO systems because of its lower latency. It is also shown that large receiver buffers and intermediate buffers can alleviate the effect of abrupt delay changes in satellite networks.