ZyXEL 793H 用户指南

 Chapter 13 Bandwidth Management

P-793H User’s Guide

You can set the bandwidth management speed for an interface higher than the interface’s 
actual transmission speed. Higher priority traffic gets to use up to its allocated bandwidth, 
even if it takes up all of the interface’s available bandwidth. This could stop lower priority 
traffic from being sent. The following is an example.

If you use VoIP and NetMeeting at the same time, the device allocates up to 500 Kbps of 
bandwidth to each of them before it allocates any bandwidth to FTP. As a result, FTP can only 
use bandwidth when VoIP and NetMeeting do not use all of their allocated bandwidth.
Suppose you try to browse the web too. In this case, VoIP, NetMeeting and FTP all have 
higher priority, so they get to use the bandwidth first. You can only browse the web when 
VoIP, NetMeeting, and FTP do not use all 1000 Kbps of available bandwidth.

The following table describes the priorities that you can apply to traffic that the ZyXEL 
Device forwards out through an interface.

Click Advanced > Bandwidth MGMT to open the screen as shown next. 
Enable bandwidth management on an interface and set the maximum allowed bandwidth for 
that interface. 

Table 65   Over Allotment of Bandwidth Example

Actual outgoing bandwidth available on the interface: 1000 kbps

Root Class: 1500 kbps  (same 

as Speed setting)

VoIP traffic (Service = SIP): 500 Kbps

High

NetMeeting traffic (Service = H.323): 500 kbps

High

FTP (Service = FTP): 500 Kbps

Medium

Table 66   Bandwidth Management Priorities

High

Typically used for voice traffic or video that is especially sensitive to jitter (jitter 

is the variations in delay).

Mid 

Typically used for “excellent effort” or better than best effort and would include 

important business traffic that can tolerate some delay.

Low

This is typically used for non-critical “background” traffic such as bulk 

transfers that are allowed but that should not affect other applications and 

users.