Users Guide

Create a QoS Policy
There are two types of QoS policies — input and output.
Input QoS policies regulate Layer 3 and Layer 2 ingress trac. The regulation mechanisms for input QoS policies are rate policing and
setting priority values.
• Layer 3 — QoS input policies allow you to rate police and set a DSCP or dot1p value. In addition, you can congure a drop precedence
for incoming packets based on their DSCP value by using a DSCP color map. For more information, see DSCP Color Maps.
• Layer 2 — QoS input policies allow you to rate police and set a dot1p value.
Output QoS policies regulate Layer 3 egress trac. The regulation mechanisms for output QoS policies are rate limiting, rate shaping, and
WRED.
NOTE: When changing a "service-queue" conguration in a QoS policy map, all QoS rules are deleted and re-added automatically
to ensure that the order of the rules is maintained. As a result, the Matched Packets value shown in the show qos
statistics command is reset.
NOTE: To avoid issues misconguration causes, Dell Networking recommends conguring either DCBX or Egress QoS features,
but not both simultaneously. If you enable both DCBX and Egress QoS at the same time, the DCBX conguration is applied and
unexpected behavior occurs on the Egress QoS.
Creating an Input QoS Policy
To create an input QoS policy, use the following steps.
1 Create a Layer 3 input QoS policy.
CONFIGURATION mode
qos-policy-input
Create a Layer 2 input QoS policy by specifying the keyword layer2 after the qos-policy-input command.
2 After you create an input QoS policy, do one or more of the following:
Conguring Policy-Based Rate Policing
Setting a DSCP Value for Egress Packets
Setting a dot1p Value for Egress Packets
Conguring Policy-Based Rate Policing
To congure policy-based rate policing, use the following command.
• Congure rate police ingress trac.
QOS-POLICY-IN mode
rate-police
Setting a DSCP Value for Egress Packets
In an input QoS policy, you can set a DSCP value for egress packets based on ingress QoS classication.
The 6–bits that are used for DSCP are also used to identify the queue in which trac is buered. When you set a DSCP value, Dell
Networking OS displays an informational message advising you of the queue to which you should apply the QoS policy (using the
service-queue from POLICY-MAP-IN mode). If you apply the QoS policy to a queue other than the one specied in the informational
message, Dell Networking OS replaces the rst 3–bits in the DSCP eld with the queue ID you specied.
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Quality of Service (QoS)