Addendum

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
The capability to configure 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:
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 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 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 mechanism to configure a weight factor for WRED and ECN functionality for backplane ports is
supported on the S6000 platform. However, this mechanism to configure a weight for WRD and ECN
functionality for front-end ports is supported on the S6000 and Z9000 platforms.
Weighted random early detection (WRED) congestion avoidance mechanism 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 656 or a few types of traffic,
leaving no space for other types. You can apply a WRED profile to a policy-map so that 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. Explicit Congestion Notification (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 this functionality of ECN to mark the packets and reduce the rate of
sending packets in a congested, heavily-loaded network.
In a best-effort network topology, data packets are transmitted in a manner in which latency or
throughput are not maintained to be at the effective, most-optimal 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
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Quality of Service (QoS)