Long round-trip time (RTT)

Satellite links have an average RTT of around 530ms to the first hop . TCP uses the slow - start mechanism at the start of a connection to find the appropriate TCP/IP parameters for that connection . Time spent in the slow-start stage is propriational to the RTT , and for a satellite link it means that TCP stays in slow-start  mode for a longer time than would otherwise be the case . This drastically decreases the throughput of short-duration TCP connections .This is can be seen in the way that a small website might take suprisingly long to load , but when a large file is transferred acceptable data rates are achieved after a while .

Furthermore , when packets are loss, TCP enters the congestion -control phase , and owing to the higher RTT , remains in this phase for a longer time , thus reducing the throughput of both short- and long duration TCP connections .