SIGCOMM '88 Symposium proceedings on Communications architectures and protocols
Virtual clock: a new traffic control algorithm for packet switching networks
SIGCOMM '90 Proceedings of the ACM symposium on Communications architectures & protocols
An approach to high-performance, high-speed data networks
IEEE Communications Magazine
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Congestion in high-speed wide area networks (HS-WAN) must be controlled in order to prevent network performance deterioration, and possible collapse. Reactive mechanisms applied to slower networks are not entirely suitable for HS-WANs due to the relatively long propagation delay in the latter. On the other hand, preventive mechanisms which have been proposed as possible solutions to this problem assume that traffic characteristics are known at the time of call setup. Window mechanisms do not depend upon such an assumption, but modifications that have been proposed to adapt it to HS-WANs fall short of the fast response required in HS-WANs. The Leaky Window (LW) mechanism is proposed in this paper as an attempt to solve this problem. This mechanism is a modification of the sliding window that permits users to transmit traffic in excess of their window sizes based on an estimate of the network load. The estimate is based on acknowledgments received within a fixed time interval. Excess traffic is distinguished by 'marking' cells. Marked cells are discarded at congested nodes. Congestion control, therefore, is a local decision executed by the congested node. Through the use of a simulation model, it is shown that the LW has an average end-to-end delay and probability of loss that is lower than the sliding window mechanism. Comparison to the Virtual Leaky Bucket (VLB) mechanism shows that at lower load (0.7), the VLB has an end-to-end delay and a probability of loss that is lower than that of the LW under the same conditions. At higher loads where congestion is a real problem, the performance of the LW is significantly better than that of the VLB.