Traffic Shaping - Cisco IE-4000 Software Configuration Manual

Configuring QoS
QoS Treatment for Performance-Monitoring Protocols
You use the shape average policy map class configuration command to specify that a class of traffic should have a
maximum permitted average rate. You specify the maximum rate in bits per second.
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Class-based-weighted-fair-queuing (CBWFQ)
You can use the bandwidth policy-map class configuration command to control the bandwidth allocated to a
specific class. Minimum bandwidth can be specified as a bit rate or a percentage of total bandwidth or of remaining
bandwidth.
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Priority queuing or class-based priority queuing
You use the priority policy-map class configuration command to specify the priority of a type of traffic over other
types of traffic. You can specify strict priority for the high-priority traffic and allocate any excess bandwidth to other
traffic queues, or specify priority with unconditional policing of high-priority traffic and allocate the known remaining
bandwidth among the other traffic queues.
— To configure strict priority, use only the priority policy-map class configuration command to configure the
priority queue. Use the bandwidth remaining percent policy-map class configuration command for the other
traffic classes to allocate the excess bandwidth in the desired ratios.
— To configure priority with unconditional policing, configure the priority queue by using the priority policy-map
class configuration command and the police policy-map class configuration command to unconditionally
rate-limit the priority queue. In this case, you can configure the other traffic classes with bandwidth or shape
average, depending on requirements.
These sections contain additional information about scheduling:
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Traffic Shaping, page 594
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Class-Based Weighted Fair Queuing, page 595
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Priority Queuing, page 596

Traffic Shaping

Traffic shaping is a traffic-control mechanism similar to traffic policing. While traffic policing is used in input policy maps,
traffic shaping occurs as traffic leaves an interface. The switch can apply class-based shaping to classes of traffic leaving
an interface and port shaping to all traffic leaving an interface. Configuring a queue for traffic shaping sets the maximum
bandwidth or peak information rate (PIR) of the queue.
Note: You cannot configure traffic shaping (shape average) and CBWFQ (bandwidth) or priority queuing (priority) for
the same class in an output policy map. You cannot configure traffic shaping for a traffic class when strict priority (priority
without police) is configured for another class within the output policy-map.
Class-Based Shaping
Class-based shaping uses the shape average policy-map class configuration command to limit the rate of data
transmission as the number of bits per second to be used for the committed information rate for a class of traffic. The
switch supports separate queues for three classes of traffic. The fourth queue is always the default queue for class
class-default, unclassified traffic.
Note: Configuring traffic shaping also automatically sets the minimum bandwidth guarantee or committed information
rate (CIR) of the queue to the same value as the PIR.
Port Shaping
To configure port shaping (a transmit port shaper), create a policy map that contains only a default class, and use the
shape average command to specify the maximum bandwidth for a port.
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