Delay-based Congestion Control for Networks with Large Bandwidth Delay Product

Large physics and astronomy projects require not only high bandwidth, but also real time predictable, low latency data transfer over long distances. Traditional TCP implementations have the under-utilization problem in large bandwidth delay product networks especially during the startup phase. We propose a delay-based congestion control (DCC) mechanism to solve the problem. DCC is subdivided into linear and exponential growth phases. The linear increase phase is similar to legacy TCP congestion avoidance scheme. The exponential increase phase can cause the serious problems of overshooting the capacity of the network by a large number of packets, causing massive retransmits and restricting the overall bandwidth. For this reason, the RTT status and estimated queue size is used to prevent the overshooting during the exponential growth phase. The simulation results show that DCC significantly improves the startup increasing time and the startup performance of TCP in large bandwidth delay product networks