ZyXEL Communications 2 Plus User Manual

 Chapter 19 Bandwidth Management

ZyWALL 2 Plus User’s Guide

The following table shows the amount of bandwidth that each class gets.

Suppose that all of the classes except for the administration class need more bandwidth.

• Each class gets up to its budgeted bandwidth. The administration class only uses 1024 

kbps of its budgeted 2048 kbps. 

• The ZyWALL divides the total 3072 kbps total of unbudgeted and unused bandwidth 

equally among the other classes. 1024 kbps extra goes to each so the other classes each get 
a total of 3072 kbps. 

Bandwidth borrowing allows a sub-class to borrow unused bandwidth from its parent class, 
whereas maximize bandwidth usage allows bandwidth classes to borrow any unused or 
unbudgeted bandwidth on the whole interface.
Enable bandwidth borrowing on a sub-class to allow the sub-class to use its parent class’s 
unused bandwidth. A parent class’s unused bandwidth is given to the highest priority sub-class 
first. The sub-class can also borrow bandwidth from a higher parent class (grandparent class) 
if the sub-class’s parent class is also configured to borrow bandwidth from its parent class. 
This can go on for as many levels as are configured to borrow bandwidth from their parent 
class (see 

). 

The total of the bandwidth allotments for sub-classes cannot exceed the bandwidth allotment 
of their parent class. The ZyWALL uses the scheduler to divide a parent class’s unused 
bandwidth among the sub-classes. 

Here is an example of bandwidth management with classes configured for bandwidth 
borrowing. The classes are set up based on departments and individuals within certain 
departments.

Table 105   Fairness-based Allotment of Unused and Unbudgeted Bandwidth Example

Root Class: 10240 kbps

Administration: 1024 kbps

Sales: 3072 kbps

Marketing: 3072 kbps

Research: 3072 kbps