ZyXEL Communications P-2302 User Manual

 Chapter 17 Bandwidth MGMT

P-2302HWUDL-P1 Series User’s Guide

Bandwidth borrowing allows a sub-class to borrow unused bandwidth from its parent class, 
whereas maximize bandwidth usage allows any bandwidth class 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 the parent class’s 
unused bandwidth. The parent class’s unused bandwidth is given to the highest priority sub-
class first (see 

). 

The total of the bandwidth allotments for sub-classes cannot exceed the bandwidth allotment 
of the parent class. The ZyXEL Device uses the scheduler to divide the parent class’s unused 
bandwidth among the sub-classes that have bandwidth borrowing enabled. 

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.

• The Sales class cannot borrow unused bandwidth from the Root class because the Sales 

class has bandwidth borrowing disabled.

If you configure both maximize bandwidth usage (on the interface) and bandwidth borrowing 
(on individual sub-classes), the ZyXEL Device functions as follows.

1 The ZyXEL Device sends traffic according to each bandwidth class’s bandwidth budget.
2 The ZyXEL Device assigns a parent class’s unused bandwidth to its sub-classes that 

have more traffic than their budgets and have bandwidth borrowing enabled. The 
ZyXEL Device gives priority to sub-classes of higher priority and treats classes of the 
same priority equally.

3 The ZyXEL Device assigns any remaining unused or unbudgeted bandwidth on the 

interface to any class that requires it. The ZyXEL Device gives priority to classes of 
higher priority and treats classes of the same level equally.

4 If the bandwidth requirements of all of the traffic classes are met and there is still some 

unbudgeted bandwidth, the ZyXEL Device assigns it to traffic that does not match any 
of the classes.

Table 88   Bandwidth Borrowing Example

Root Class: 

Administration: Borrowing Enabled

Sales: Borrowing Disabled

Marketing: Borrowing Enabled

Research: Borrowing Enabled