Dell S4820T, Configuration Manual

Page: 807 / 1178

Enabling QoS Rate Adjustment
By default while rate limiting, policing, and shaping, Dell Networking OS does not include the Preamble,
SFD, or the IFG fields. These fields are overhead; only the fields from MAC destination address to the CRC
are used for forwarding and are included in these rate metering calculations.
The Ethernet packet format consists of:
• Preamble: 7 bytes Preamble
• 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.
The range is from 1 to 31.
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 3.
Quality of Service (QoS)
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