Quality of Service | 869Specify an aggregate QoS policySpecify an aggregate QoS policy using the command policy-aggregate from POLICY-MAP-OUT mode.Apply an output policy map to an interfaceApply an input policy map to an interface using the command service-policy output from INTERFACEmode. You can apply the same policy map to multiple interfaces, and you can modify a policy map afteryou apply it.QoS Rate AdjustmentThe 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)By default, while rate limiting, policing, and shaping, FTOS does not include the Preamble, SFD, or theIFG fields. These fields are overhead; only the fields from MAC Destination Address to the CRC are usedfor forwarding and are included in these rate metering calculations. You can optionally include overheadfields 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-configuration.Task Command Syntax Command ModeInclude a specified number of bytes of packet overheadto include in rate limiting, policing, and shapingcalculations. For example, to include the Preamble andSFD, enter qos-rate-adjust 8. For variable lengthoverhead fields you must know the number of bytes youwant to include.qos-rate-adjust overhead-bytesDefault: DisabledC-Series and S-Series Range: 1-31E-Series Range: 1-144CONFIGURATION
