Performance study of congestion control for high-speed backbone networks

Abstract We investigate the performance of a congestion control scheme for an interconnected network where several local area networks (LAN) are connected to a high-speed backbone network via bridges. In such a network, traffic congestion may occur due to the difference of transmission speed and/or workload between the high-speed backbone and the lower speed LANs. To release congestion and to obtain high throughput, we propose a congestion control scheme and evaluate the performance via simulation. In our scheme, each bridge always informs the other bridges of the number of available spaces in its buffer. The scheme gives the highest priority in transmission to the packets of the destination bridge which has the largest available buffer spaces. Simulation results show that the scheme significantly reduces the packet loss and provides high throughput in the backbone network. Furthermore, the scheme guarantees fast packet delivery between the uncongested bridges. However, the packets destined for the congested bridge stay in the buffer for a long time due to low transmission priority and shut out the other packets destined for the uncongested bridges. To avoid this, we improve the scheme by introducing a selective packet dropping function. The enhanced scheme restricts the maximum number of the packets which have the same destination. Not only has the enhanced scheme the advantage of the previous one, but it also guarantees the delivery of a packet of which the destination is not congested.