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Chapter 15 Bandwidth MGMT
P-2304R-P1 Series User’s Guide
157
15.1.8 Bandwidth Borrowing
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 Section 15.1.8.1 on page 157).
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.
15.1.8.1 Bandwidth Borrowing Example
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.
15.1.8.2 Maximize Bandwidth Usage With Bandwidth Borrowing
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 68 Bandwidth Borrowing Example
BANDWIDTH CLASSES AND BANDWIDTH BORROWING SETTINGS
Root Class: Administration: Borrowing Enabled
Sales: Borrowing Disabled
Marketing: Borrowing Enabled
Research: Borrowing Enabled