GridFTP; Threat or Menace

TCP congestion control has come to be considered fundamental to the stability of the Internet. Congestion control specifies a limit on how fast a single flow can inject bytes into the network as a function of its loss rate; this policy, also known as TCP-friendliness is meant to ensure fair utilization of network capacity. Unfortunately, no such fairness guideline exists for the number of connections a single user can open. A user opening 'k' connections to download a single document gets 'k' times the throughput of another using just one connection through the same bottleneck. Opening multiple connections to get increased throughput appears to be emerging as a popular trend; example applications are GridFTP, Parallel FTP, Mozilla etc. Uncontrolledly opening connections can damage the stability of the Internet rendering congestion control meaningless. We propose a connection control model that advocates conscientiously limiting the number of connections opened by a single user. Our solution, based on TCP Nice, provides a mechanism that can provide improved and fair utilization in underutilized networks without compromising the stability of the Internet.