Congestion control in data transmission networks: Historical perspective

Abstract

The congestion occurs when the traffic generated by the network users exceeds the available bandwidth in the communication system. In such circumstances, not all the packets sent by the sources can be immediately relayed on the route towards their destination. Instead, they accumulate in the buffers at the intermediate nodes and wait for the bandwidth increase. If the incoming rate is not reduced (or stopped) before the queue of awaiting packets reaches its limit, typically defined by the amount of the reserved memory at the node, the new data pieces must be discarded. The lost fragments are retransmitted, which further deepens the congestion at the bottleneck point. At certain stage, the network becomes clogged with retransmissions and stops providing its services – this state is referred to as a deadlock or congestion collapse. In fact, the early communication networks frequently suffered from congestion collapse, until the development of the Jacobson’s scheme [73] for the Internet flow control.