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In releases of Dell EMC Networking OS earlier than Release 9.3(0.0), you can configure only the maximum shaping attributes,
such as the peak rate and the peak burst settings. You can now specify the committed or minimum burst and committed rate
attributes. The committed burst and committed rate values can be defined either in bytes or pps.
You can use the rate-shape pps peak-rate burst-packets command in the QoS Policy Out Configuration mode to
configure 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 configure 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 Configuration mode to configure 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 configure the committed rate and committed burst size as a measure of bytes. If
you configure the peak rate in pps, the peak burst size must also be configured as a measure of number of packets. Similarly, if
you configure the peak rate in Kbps, the peak burst size must also be configured as a measure of bytes.
Configuring Policy-Based Rate Shaping
You can configure 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 configure the peak burst and committed burst sizes. All of these settings can be configured in Kbps, Mbps, or pps.
To configure the peak and committed rates and burst sizes, perform the following steps:
1. Configure the peak rate and peak burst size in pps in QoS Policy Out Configuration mode.
QOS-POLICY-OUT mode
DellEMC(config-qos-policy-out)# rate shape pps peak-rate burst-packets
2. Alternatively, configure the peak rate and peak burst size in bytes.
QOS-POLICY-OUT mode
DellEMC(config-qos-policy-out)# rate shape Kbps peak-rate burst-KB
3. Configure the committed rate and committed burst size in pps.
QOS-POLICY-OUT mode
DellEMC(config-qos-policy-out)# rate shape pps peak-rate burst-packets committed pps
committed-rate burst-packets
4. Alternatively, configure the committed rate and committed burst size in bytes.
QOS-POLICY-OUT mode
DellEMC(config-qos-policy-out)# rate shape Kbps peak-rate burst-KB committed Kbps
committed-rate burst-KB
Configuring Weights and ECN for WRED
The WRED congestion avoidance functionality drops packets to prevent buffering resources from being consumed. 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 few types of traffic,
leaving no space for other types. You can apply a WRED profile to a policy-map so that the specified traffic can be prevented
from consuming too much of the BTM resources.
WRED drops packets when the average queue length exceeds the configured 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 configure ECN for WRED, devices employ ECN to mark the packets and reduce the rate of sending packets in
a congested network.
In a best-effort network topology, data packets are transmitted in a manner in which latency or throughput is not maintained
to be at an effective level. Packets are dropped when the network experiences a large traffic load. This best-effort 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.
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Quality of Service (QoS)