ZyXEL Communications P-2304R-P1 Series Manuel D’Utilisation

 Chapter 15 Bandwidth MGMT

P-2304R-P1 Series User’s Guide

With the priority-based scheduler, the ZyXEL Device forwards traffic from bandwidth classes 
according to the priorities that you assign to the bandwidth classes. The larger a bandwidth 
class’s priority number is, the higher the priority. Assign real-time applications (like those 
using audio or video) a higher priority number to provide smoother operation.
The ZyXEL Device divides bandwidth equally among bandwidth classes when using the 
fairness-based scheduler; thus preventing one bandwidth class from using all of the interface’s 
bandwidth. 

This option allows the ZyXEL Device to divide up any available bandwidth on the interface 
(including unallocated bandwidth and any allocated bandwidth that a class is not using) among 
the bandwidth classes that require more bandwidth. 
When you enable maximize bandwidth usage, the ZyXEL Device first makes sure that each 
bandwidth class gets up to its bandwidth allotment. Next, the ZyXEL Device divides up an 
interface’s available bandwidth (bandwidth that is unbudgeted or unused by the classes) 
depending on how many bandwidth classes require more bandwidth and on their priority 
levels. When only one class requires more bandwidth, the ZyXEL Device gives extra 
bandwidth to that class. 
When multiple classes require more bandwidth, the ZyXEL Device gives the highest priority 
classes the available bandwidth first (as much as they require, if there is enough available 
bandwidth), and then to lower priority classes if there is still bandwidth available. The ZyXEL 
Device distributes the available bandwidth equally among classes with the same priority level. 

Do the following three steps to configure the ZyXEL Device to allow bandwidth for traffic 
that is not defined in a bandwidth filter.

1 Leave some of the interface’s bandwidth unbudgeted.
2 Do not enable the interface’s Maximize Bandwidth Usage option.
3 Do not enable bandwidth borrowing on the sub-classes (see 

Here is an example of a ZyXEL Device that has maximize bandwidth usage enabled on an 
interface. The following table shows each bandwidth class’s bandwidth budget. The classes 
are set up based on subnets. The interface is set to 10240 kbps. Each subnet is allocated 2048 
kbps. The unbudgeted 2048 kbps allows traffic not defined in any of the bandwidth filters to 
go out when you do not select the maximize bandwidth option.

Table 65   Maximize Bandwidth Usage Example

Root Class: 10240 kbps

Administration: 2048 kbps

Sales: 2048 kbps

Marketing: 2048 kbps

Research: 2048 kbps