Reference Guide

Quality of Service (QoS) | 739
Specifying an aggregate QoS policy:
Specify an aggregate QoS policy using the command policy-aggregate from POLICY-MAP-OUT mode.
Applying an output policy map to an interface:
Apply an input policy map to an interface using the command service-policy output from INTERFACE
mode. You can apply the same policy map to multiple interfaces, and you can modify a policy map after
you apply it.
QoS Rate Adjustment
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)
By default, while rate limiting, policing, and shaping, FTOS 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. You can optionally include overhead
fields 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.
Strict-priority Queueing
You can assign strict-priority to one unicast queue, 1-7, using the command strict-priority from
CONFIGURATION mode. Strict-priority means that FTOS dequeues all packets from the assigned queue
before servicing any other queues.
•The
strict-priority supersedes bandwidth-percentage an bandwidth-weight percentage configurations.
Task Command Syntax Command Mode
Include a specified number of bytes of packet overhead
to include in rate limiting, policing, and shaping
calculations. For example, to include the Preamble and
SFD, enter
qos-rate-adjust 8. For variable length
overhead fields you must know the number of bytes you
want to include.
qos-rate-adjust overhead-bytes
Default: Disabled
S5000 Range: 1-31
CONFIGURATION