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NTCP: Network assisted TCP for long delay satellite network

With the reduced cost of launching a satellite and the development of satellite communication technology, satellite networking is regaining people's focus both from industry and academia. Among them, GEO satellites, with the benefits of large and stable coverage area, have already been used for commercial broadband communication. However, the inherent long transmission range makes the propagation delay of satellite (especially GEO) link much longer than its terrestrial counterpart. This poses challenges to TCP especially for small object transfer which takes only several RTTs. The default initial cwnd(congestion window) size of 10 has been proposed by Google[1] and enabled by Linux for many years but it is unsuitable for satellite environment. In this paper, we propose NTCP: Network assisted TCP for long delay satellite network. We introduce a ground- based SDN architecture for satellite network, propose a method to calculate the upper bound of initial cwnd based on the flow numbers and link bandwidth of each link, and scale the initial cwnd by multiplying the initial bandwidth of initial spreading[10] with link RTT. The efficacy of our scheme is proved in the evaluation part.