In a congested network, response time slows with reduced network throughput. Congestion occurs when bandwidthis insufficient and network data traffic exceeds capacity.
Data packet loss from congestion is partially countered by aggressive network protocol retransmission, which maintains a network congestion state after reducing the initial data load.
Congestion has been described as a fundamental effect of limited network resources, especially router processing time and link throughput.
Networks use congestion control and congestion avoidance techniques to try to avoid collapse. These include exponential backoff in protocols such as CSMA/CA in 802.11 and the similar CSMA/CD in the original Ethernet, window reduction in TCP, and fair queueing in devices such as routers and network switches.
Example of usage – “Cumulative router processing time greatly impacts network congestion. In fact, intermediate routers may actually discard data packets when they exceed their handling capability. When this occurs, additional data packets may be sent to make up for unreceived packets, which exacerbates the problem.”