User's Manual

P-660HW-Tx v3 Series User’s Guide
253
CHAPTER 16
Quality of Service (QoS)
16.1 Overview
Use the QoS screens to set up your ZyXEL Device to use QoS for traffic
management.
Quality of Service (QoS) refers to both a network’s ability to deliver data with
minimum delay, and the networking methods used to control bandwidth. QoS
allows the ZyXEL Device to group and prioritize application traffic and fine-tune
network performance.
Without QoS, all traffic data are equally likely to be dropped when the network is
congested. This can cause a reduction in network performance and make the
network inadequate for time-critical applications such as video-on-demand.
The ZyXEL Device assigns each packet a priority and then queues the packet
accordingly. Packets assigned with a high priority are processed more quickly than
those with low priorities if there is congestion, allowing time-sensitive applications
to flow more smoothly. Time-sensitive applications include both those that require
a low level of latency (delay) and a low level of jitter (variations in delay) such as
Voice over IP (VoIP) or Internet gaming, and those for which jitter alone is a
problem such as Internet radio or streaming video.
16.1.1 What You Can Do in the QoS Screens
•Use the General screen (Section 16.2 on page 258) to enable QoS on the
ZyXEL Device, decide allowable bandwidth using QoS and configure priority
mapping settings for traffic that does not match a custom class.
•Use the Class Setup screen (Section 16.3 on page 259) to set up classifiers to
sort traffic into different flows and assign priority and define actions to be
performed for a classified traffic flow.
•Use the Monitor screen (Section 16.4 on page 265) to view the ZyXEL Device’s
QoS-related packet statistics.