Analysis of Random Drop for Gateway Congestion Control.

摘要

The growing demand on the Internet has prompted the need for more effective congestion control policies. Currently No Gateway Policy is used to relieve and signal congestion, which leads to a degradation of overall network performance. This thesis uses network simulation to illustrate the character of Internet congestion and its causes. It considers a newly proposed gateway congestion control policy, called Random Drop, as a promising solution. Random Drop relieves resource congestion upon buffer overflow by choosing a random packet from the service queue to be dropped. The random choice should result in a drop distribution proportional to the bandwidth distribution among all contending TCP connections. The simulation experiments demonstrate several shortcomings with this policy. Because Random Drop is a congestion control policy, which is not applied until congestion has already occurred, it usually results in a high drop rate that hurts too many connections including well-behaved ones. A modification of Random Drop to do congestion avoidance by applying the policy early was also proposed. Early Random Drop to do congestion avoidance by applying the policy early was also proposed. Early Random Drop has the advantage of avoiding the high drop rate of buffer overflow. The early application of the policy removes the pressure of congestion relief and allows more accurate signaling of congestion. Algorithms for the dynamic adjustment of the parameters of Early Random Drop to suite the current network load must still be developed. Keywords: Computer communications; Data transfer; Computer communications network. (kt)