Administrator Guide
• Cyclic redundancy check (CRC): 4 bytes
• Inter-frame gap (IFG): (variable)
You can optionally include overhead elds in rate metering calculations by enabling QoS rate adjustment.
QoS rate adjustment is disabled by default, and no qos-rate-adjust is listed in the running-conguration
• Include a specied 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, enter qos-rate-adjust 8. For variable length overhead elds, know the
number of bytes you want to include.
The default is disabled.
The range is from 1 to 31.
Enabling Strict-Priority Queueing
Strict-priority means that the Dell Networking OS de-queues all packets from the assigned queue before servicing any other queues.
• The strict-priority supersedes bandwidth-percentage and bandwidth-weight percentage congurations.
• A queue with strict priority can starve other queues in the same port-pipe.
• If more than two strict priority queues are congured, the strict priority queue with a higher queue number is scheduled rst.
• Assign strict priority to one unicast queue.
CONFIGURATION mode
strict-priority
The range is from 1 to 3.
Weighted Random Early Detection
The WRED congestion avoidance mechanism drops packets to prevent buering resources from being consumed.
Trac 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 buer and trac manager (BTM) (ingress or egress) can be consumed by only one or a few types of trac,
leaving no space for other types. You can apply a WRED prole to a policy-map so that specied trac can be prevented from
consuming too much of the BTM resources.
WRED uses a prole to specify minimum and maximum threshold values. The minimum threshold is the allotted buer space for
specied trac, for example, 1000KB on egress. If the 1000KB is consumed, packets are dropped randomly at an exponential rate
until the maximum threshold is reached (as shown in the following illustration); this procedure is the early detection part of WRED. If
the maximum threshold, for example, 2000KB, is reached, all incoming packets are dropped until the buer space consumes less
than 2000KB of the specied trac.
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Quality of Service (QoS)