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Dell Configuration Guide for the S4048–ON System 9.14.2.4

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Enabling QoS Rate Adjustment

By default while rate limiting, policing, and shaping, Dell EMC 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.

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