TCP-Cherry: A new approach for TCP congestion control over satellite IP networks

TCP performance is vulnerable to long delays and errors over satellite links despite their potential for ubiquitous coverage. In this paper, we therefore propose a new TCP congestion control mechanism, TCP-Cherry, to improve TCP performance over satellite IP networks. The basic idea is to probe the network for available resources using data segments that do not put the network into congestion. To this goal, TCP-Cherry deploys a new type of low-priority data segments, namely, supplement segments that in addition to probing the network, carry data not yet transmitted as regular data segments. Our major contributions in this work include two new algorithms, Fast-Forward Start and First-Aid Recovery, for congestion control in the presence of data segments belonging to two different levels of priority. Another unique feature of our scheme is the mechanism for selection of supplement segments which keeps the overhead of duplicate transmission minimum. We also propose a simple scheme for avoiding gradual decrease of TCP congestion window owing to recurring loss of probing segments. Simulation results show that our proposed TCP-Cherry yields upto a maximum improvement of more than 150% in goodput compared with other existing schemes. We also observe that TCP-Cherry maintains a fair share of bandwidth among competing TCP connections. In addition, the supplement segments used for probing the network induce the minimal network overhead.