9 bandwidth borrowing – ZyXEL Communications ZyXEL ZyWALL 5 User Manual
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ZyWALL 5 User’s Guide
Chapter 19 Bandwidth Management
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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 sales and marketing are first to get extra bandwidth because they have the highest
priority (6). If they each require 1536 kbps or more of extra bandwidth, the ZyWALL
divides the total 3072 kbps total of unbudgeted and unused bandwidth equally between
the sales and marketing departments (1536 kbps extra to each for a total of 3584 kbps for
each) because they both have the highest priority level.
• Research requires more bandwidth but only gets its budgeted 2048 kbps because all of the
unbudgeted and unused bandwidth goes to the higher priority sales and marketing
classes.
19.8.2.2 Fairness-based Allotment of Unused and Unbudgeted Bandwidth
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
19.9 Bandwidth Borrowing
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 (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.
Table 104 Fairness-based Allotment of Unused and Unbudgeted Bandwidth Example
BANDWIDTH CLASSES AND ALLOTMENTS
Root Class: 10240 kbps
Administration: 1024 kbps
Sales: 3072 kbps
Marketing: 3072 kbps
Research: 3072 kbps