A Delay Based Approach for Congestion Avoidance in Interconnected Heterogeneous Computer Networks

摘要

In heterogeneous networks, achieving congestion avoidance is difficultbecause the congestion feedback from one subnetwork may have no meaning tosource on other other subnetworks. We propose using changes in round-trip delayas an implicit feedback. Using a black-box model of the network, we derive anexpression for the optimal window as a function of the gradient of thedelay-window curve. The problems of selfish optimum and social optimum are also addressed. It isshown that without a careful design, it is possible to get into a racecondition during heavy congestion, where each user wants more resources thanothers, thereby leading to a diverging congestion It is shown that congestion avoidance using round trip delay is a promisingapproach. The aproach has the advantage that there is absolutely no overheadfor the network itself. It is exemplified by a simple scheme. The performanceof the scheme is analyzed using a simulation model. The scheme is shown to beefficient, fair, convergent and adaptive to changes in network configuration. The scheme as described works only for networks that can ne modelled withqueueing servers with constant service times. Further research is required toextend it for implementation in practical networks. Several directions forfuture research have beensuggested.