Enabling Strict-Priority Queueing; Weighted Random Early Detection - Dell Z9000 Configuration Manual

• Start frame delimiter (SFD): 1 byte
• Destination MAC address: 6 bytes
• Source MAC address: 6 bytes
• Ethernet Type/Length: 2 bytes
• Payload: (variable)
• Cyclic redundancy check (CRC): 4 bytes
• Inter-frame gap (IFG): (variable)
You can optionally include overhead fields in rate metering calculations by enabling QoS rate adjustment.
QoS rate adjustment is disabled by default.
• Specify the number of bytes of packet overhead to include in rate limiting, policing, and shaping
calculations.
CONFIGURATION mode
qos-rate-adjust overhead-bytes
For example, to include the Preamble and SFD, type qos-rate-adjust 8. For variable length
overhead fields, know the number of bytes you want to include.
The default is disabled.

Enabling Strict-Priority Queueing

Strict-priority means that Dell Networking OS de-queues all packets from the assigned queue before
servicing any other queues.
• The strict-priority supersedes bandwidth-percentage configuration.
• A queue with strict priority can starve other queues in the same port-pipe.
• Assign strict priority to one unicast queue.
CONFIGURATION mode
strict-priority
The range is from 1 to 7.

Weighted Random Early Detection

Weighted random early detection (WRED) is supported on the Z9000 platform.
The 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 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 uses a profile to specify minimum and maximum threshold values. The minimum threshold is the
allotted buffer space for specified traffic, for example, 1000KB on egress. If the 1000KB is consumed,
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Quality of Service (QoS)