Allocating Bandwidth

Guaranteed minimum bandwidth is allocated in percentages or in bits per second. The root class has 100% of the bandwidth configured for an interface. Each child class of the root class is allocated a share of root's bandwidth. The child classes of those classes are allocated a share of their parent's bandwidth. The bandwidth you allocate is the minimum guaranteed bandwidth for a particular class. You can also set a ceiling, or maximum bandwidth if you want.

The rest of this section is an example of how to allocate bandwidth to a hierarchy of classes. Assume you have the following class hierarchy:

Figure 3-2 Example of Allocating Bandwidth: Class Hierarchy

Before you allocate any bandwidth to child classes, the root class has 100%:

Figure 3-3 Example of Allocating Bandwidth: Root Allocated 100%

Share the bandwidth allocated to the root class with the child classes of the root class, 1, 2, and 3:

Figure 3-4 Example of Allocating Bandwidth: Child Classes of Root

The root class itself requires some bandwidth to handle traffic allocated to it, therefore, do not allocate 100% of the bandwidth to the child classes. The root class will use the 5% that is left.

For each child class, share the bandwidth allocated with their own child classes. For example, share the 30% allocated to class 1 with child classes 1.1 and 1.2. The figure in brackets shows the amount of bandwidth left-over once you have allocated bandwidth to the child classes. This left-over bandwidth effectively becomes the guaranteed minimum bandwidth for the parent class.

Figure 3-5 Example of Allocating Bandwidth: Second Level Classes

Continue sharing the bandwidth allocated to each class with its child classes until all classes have an allocation:

Figure 3-6 Example of Allocating Bandwidth: Allocation Complete

When specifying the bandwidth allocated to a class in the configuration file or using batool, you must specify the aggregate bandwidth allocated to a class and all its descendants. For example, for class 3.1, specify 20%, and for class 1, specify 30%.