Home QoS QoS General Random Early Detection (RED)?

Random Early Detection (RED) is a congestion avoidance mechanism that takes advantage of TCP's congestion control mechanism.
When it comes to Quality of Service, there are 2 separate approaches. The first is congestion management, which is setting up queues to ensure that the higher priority traffic gets serviced in times of congestion. The other is congestion avoidance, which works by dropping packets before congestion on the link occurs.
RED takes a proactive approach to congestion. Instead of waiting until the queue is completely filled up, RED starts dropping packets with a non-zero drop probability after the average queue size exceeds a certain minimum threshold. A drop probability ensures that RED randomly drops packets from only a few flows, avoiding global synchronization. A packet drop is meant to signal the TCP source to slow down. Responsive TCP flows slow down after packet loss by going into slow start mode.


Reference: ‘IP Quality of Service’ from, Cisco Press

Last Updated (Tuesday, 05 May 2009 21:40)

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