Dell PowerEdge FN I/O Module Configuration Guide 9.10(0.0)

Traffic is a mixture of various kinds of packets. The rate at which some types of packets arrive might be greater than others. In this case, the space on the buffer and traffic manager (BTM) (ingress or egress) can be consumed by only one or a few types of traffic, leaving no space for other types. You can apply a WRED profile to a policy-map so that specified traffic can be prevented from consuming too much of the BTM resources.

WRED uses a profile to specify minimum and maximum threshold values. The minimum threshold is the allotted buffer space for specified traffic, for example, 1000KB on egress. If the 1000KB is consumed, packets are dropped randomly at an exponential rate until the maximum threshold is reached (as shown in the following illustration); this procedure is the early detection part of WRED. If the maximum threshold, for example, 2000KB, is reached, all incoming packets are dropped until the buffer space consumes less than 2000KB of the specified traffic.

Figure 1. Packet Drop Rate for WRED

You can create a custom WRED profile or use one of the five pre-defined profiles.