Cisco Cisco IOS Software Release 12.2(27)SBC

Configuring traffic policing and shaping on the basis of a percentage of bandwidth is accomplished by 
using the police (percent) and shape (percent) commands. For more information about these commands, 
see the 

 section later in this document.

The purpose of the burst parameters (bc and be) is to drop packets gradually, as is done with Weighted 
Random Early Detection (WRED), and to avoid tail drop. Setting sufficiently high burst values helps to 
ensure good throughput.

This feature allows you the option of specifying the committed (conform) burst (bc) size and the excess 
(peak) burst (be) as milliseconds (ms) of the class bandwidth when you configure traffic shaping. The 
number of milliseconds is used to calculate the number of bytes to be used by the QoS: Percentage-Based 
Shaping feature. 

Specifying these burst sizes in milliseconds is accomplished by using the bc and be keywords (and their 
associated arguments) of the police (percent) and shape (percent) commands. 

For more information about these commands, see the 

 section later in this 

document.

See the following sections for configuration tasks for the QoS: Percentage-Based Shaping feature. Each 
task in the list is identified as either required or optional.

 (required)

 (optional)

A class map is used to organize traffic into specific categories or classes. These categories or classes of 
traffic are associated with a traffic policy or policy map. In turn, the policy map is used in conjunction 
with the class map to apply a specific QoS feature to the traffic. In this instance, the QoS feature of 
percentage-based shaping will be applied.

To configure a class map and associate the class map with a specific policy map, perform the following 
steps.

 

class {class-name | class-default}

shape {average | peak} percent percentage [sustained-burst-in-msec ms] [be excess-burst-in-msec 
ms] [bc committed-burst-in-msec ms]