Users Guide

You can use the rate-shape pps peak-rate burst-packets command in the QoS Policy Out Conguration mode to congure
the peak rate and burst size as a measure of pps. Alternatively, you can use the rate shape kbps peak-rate burst-KB command
to congure the peak rate and peak burst size as a measure of bytes.
Similarly, you can use the rate-shape pps peak-rate burst-packets committed pps committed-rate burst-
packets command in the QoS Policy Out Conguration mode to congure the committed rate and committed burst size as a measure of
pps. Alternatively, you can use the rate shape kbps peak-rate burst-KB committed kbps committed-rate burst-
KB command to congure the committed rate and committed burst size as a measure of bytes. If you congure the peak rate in pps, the
peak burst size must also be congured as a measure of number of packets. Similarly, if you congure the peak rate in Kbps, the peak burst
size must also be congured as a measure of bytes.
Conguring Policy-Based Rate Shaping
You can congure the rate shaping for QoS output policies in packets per second (pps).
You can explicitly specify the rate shaping functionality for QoS output policies as peak rate and committed rate attributes. You can also
congure the peak burst and committed burst sizes. All of these settings can be congured in Kbps, Mbps, or pps.
To congure the peak and committed rates and burst sizes, perform the following steps:
1 Congure the peak rate and peak burst size in pps in QoS Policy Out Conguration mode.
QOS-POLICY-OUT mode
Dell(config-qos-policy-out)# rate shape pps peak-rate burst-packets
2 Alternatively, congure the peak rate and peak burst size in bytes.
QOS-POLICY-OUT mode
Dell(config-qos-policy-out)# rate shape Kbps peak-rate burst-KB
3 Congure the committed rate and committed burst size in pps.
QOS-POLICY-OUT mode
Dell(config-qos-policy-out)# rate shape pps peak-rate burst-packets committed pps committed-
rate burst-packets
4 Alternatively, congure the committed rate and committed burst size in bytes.
QOS-POLICY-OUT mode
Dell(config-qos-policy-out)# rate shape Kbps peak-rate burst-KB committed Kbps committed-rate
burst-KB
Conguring Weights and ECN for WRED
The WRED congestion avoidance functionality drops packets to prevent buering resources from being consumed. Trac 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 buer
and trac manager (BTM) (ingress or egress) can be consumed by only one or few types of trac, leaving no space for other types. You
can apply a WRED prole to a policy-map so that the specied trac can be prevented from consuming too much of the BTM resources.
WRED drops packets when the average queue length exceeds the congured threshold value to signify congestion. ECN is a capability that
enhances WRED by marking the packets instead of causing WRED to drop them when the threshold value is exceeded. If you congure
ECN for WRED, devices employ ECN to mark the packets and reduce the rate of sending packets in a congested network.
In a best-eort network topology, data packets are transmitted in a manner in which latency or throughput is not maintained to be at an
eective level. Packets are dropped when the network experiences a large trac load. This best-eort network deployment is not suitable
for applications that are time-sensitive, such as video on demand (VoD) or voice over IP (VoIP) applications. In such cases, you can use
ECN in conjunction with WRED to resolve the dropping of packets under congested conditions.
Quality of Service (QoS)
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