Reference Guide

Configuring Policy-Based Rate Shaping
Configuration of rate shaping for QoS output policies in packets per second (pps) is supported on the
S6000 platform.
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
Dell(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
Dell(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
Dell(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
Dell(config-qos-policy-out)# rate shape Kbps peak-rate burst-KB committed
Kbps committed-rate burst-KB
Configuring Weights and ECN for WRED
The feature to configure a weight factor for weighted random early detection (WRED) and Explicit
Congestion Notification (ECN) functionality for backplane ports is supported on the S6000 platform.
Additionally, the feature to configure a weight for WRED and ECN functionality for front-end ports is
supported on the S6000 platform.
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
Quality of Service (QoS)
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