Reference Guide

Quality of Service | 817
Apply a WRED profile to traffic
Once you create a WRED profile you must specify to which traffic FTOS should apply the profile.
FTOS assigns a color (also called drop precedence)—red, yellow, or green—to each packet based on it
DSCP value before queuing it. DSCP is a 6 bit field. Dell Force10 uses the first three bits of this field (DP)
to determine the drop precedence. DP values of 110 and 100 map to yellow, and all other values map to
green. If you do not configure FTOS to honor DSCP values on ingress (refer to Honor DSCP values on
ingress packets) see all traffic defaults to green drop precedence.
Assign a WRED profile to either yellow or green traffic from QOS-POLICY-OUT mode using the
command
wred.
Configure WRED for Storm Control
Configure WRED for Storm Control is supported only on platform e
Storm control limits the percentage of the total bandwidth that broadcast traffic can consume on an
interface (if configured locally) or on all interfaces (if configured globally). For
storm-control broadcast 50
out, the total bandwidth that broadcast traffic can consume on egress on a 1Gbs interface is 512Mbs. The
method by which packets are selected to be dropped is the "tail-drop" method, where packets exceeding
the specified rate are dropped.
WRED can be used in combination with storm control to regulate broadcast and unknown-unicast traffic.
This feature is available through an additional option in command
storm-control [broadcast |
unknown-unicast] at CONFIGURATION. Refer to the FTOS Command Line Reference for information on
using this command.
Using the command
storm-control broadcast 50 out wred-profile, for example, first the total bandwidth that
broadcast traffic can consume is reduced to 50% of line rate. Even though broadcast traffic is restricted, the
rate of outgoing broadcast traffic might be greater than other traffic, and if so, broadcast packets would
consume too much buffer space. So, the
wred-profile option is added to limit the amount of buffer space
that broadcast traffic can consume.
Display Default and Configured WRED Profiles
Display default and configured WRED profiles and their threshold values using the command show qos
wred-profile from EXEC mode, as shown in the example below.
FTOS#show qos wred-profile
Wred-profile-name min-threshold max-threshold
wred_drop 0 0
wred_ge_y 1000 2000
wred_ge_g 2000 4000
wred_teng_y 4000 8000
wred_teng_g 8000 16000