In the second of three QoS videos, we discuss the theory of Weighted Random Early Detection (WRED), using a Styrofoam cup, water, and a Sharpie.

WRED is considered a congestion avoidance mechanism, in that it attempts to prevent an interface's output queue from ever filling to capacity (which would result in some serious side effects). WRED is targeted towards TCP flows (as opposed to UDP flows). So, while WRED is not applicable to a voice queue (since Real-time Transport Protocol (RTP) is carried via UDP), it can intelligently prevent varous data queues from overflowing. I hope you enjoy the video!