Weighted random early detection (WRED) is a queueing discipline for a network scheduler suited for congestion avoidance.
[1] It is an extension to random early detection (RED) where a single queue may have several different sets of queue thresholds.
A queue buildup will cause the lower priority packets to be dropped, hence protecting the higher priority packets in the same queue.
On Cisco switches WRED is restricted to Non-IP traffic will be dropped more often than TCP/IP traffic because it is treated with the lowest possible precedence.
WRED proceeds in this order when a packet arrives: The average queue size depends on the previous average as well as the current size of the queue.
The previous average is more important for high values of
Peaks and lows in queue size are smoothed by a high value.