Random early detection

Random early detection (RED), also known as random early discard or random early drop, is a <a href="/facts/Active_Queue_Management/dPk4QqtM">queuing discipline</a> for a <a href="/facts/Network_scheduler/7URA71LE">network scheduler</a> suited for <a href="/facts/Network_congestion_avoidance/9ohkRMso">congestion avoidance</a>.
In the conventional <a href="/facts/Tail_drop/6HRcH1lk">tail drop</a> algorithm, a <a href="/facts/Router_(computing)/Nh5cIyVf">router</a> or other <a href="/facts/Computer_networking_device/ck0rIkXA">network component</a> buffers as many packets as it can, and simply drops the ones it cannot buffer. If buffers are constantly full, the network is <a href="/facts/Network_congestion/9ohkRMso">congested</a>. Tail drop distributes buffer space unfairly among traffic flows. Tail drop can also lead to <a href="/facts/TCP_global_synchronization/XxYy4JBg">TCP global synchronization</a> as all <a href="/facts/Transmission_Control_Protocol/WW4sPrt9">TCP</a> connections "hold back" simultaneously, and then step forward simultaneously. Networks become under-utilized and flooded—alternately, in waves. 
RED addresses these issues by pre-emptively dropping packets before the buffer becomes completely full. It uses predictive models to decide which packets to drop. It was invented in the early 1990s by <a href="/facts/Sally_Floyd/f6QUVc8H">Sally Floyd</a> and <a href="/facts/Van_Jacobson/WD2r6Mll">Van Jacobson</a>.

Random early detection open-in-new

Random early detection