What are the difficulties of the current TCP at large windows?
Four difficulties contribute to the poor performance of current TCP implementation in networks with large bandwidth-delay product: • At the packet level, linear increase by one packet per Round-Trip Time (RTT) is too slow, and multiplicative decrease per loss event is too drastic. • At the flow level, maintaining large average congestion windows requires an extremely small equilibrium loss probability that is hard to achieve in practice. • At the packet level, oscillation is unavoidable because of the binary nature of the congestion signal (packet loss). • At the flow level, the dynamics is unstable, leading to severe oscillations that can only be reduced by the accurate estimation of packet loss probability and a stable design of the flow dynamics. The first two problems are really the same problem that manifests itself at the packet and flow levels. The last two problems, however, are of different nature and must be solved using different means. Oscillations at the packet level can b
