Quality Of Service (Qos); Chapter 17 Quality Of Service (Qos); Overview; What You Can Do In The Qos Screens - ZyXEL Communications P-793H v3 User Manual

17.1 Overview

Use the QoS screens to set up your P-79X 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 P-79X 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 P-79X 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.

17.1.1 What You Can Do in the QoS Screens

• Use the General screen
allowable bandwidth using QoS and configure priority mapping settings for traffic that does not
match a custom class.
• Use the Class Setup screen
different flows and assign priority and define actions to be performed for a classified traffic flow.

17.1.2 What You Need to Know About QoS

QoS versus Cos
QoS is used to prioritize source-to-destination traffic flows. All packets in the same flow are given
the same priority. Class of Service (CoS) is a way of managing traffic in a network by grouping
similar types of traffic together and treating each type as a class. You can use CoS to give different
priorities to different packet types.
CoS technologies include IEEE 802.1p layer 2 tagging and Differentiated Services (DiffServ or DS).
IEEE 802.1p tagging makes use of three bits in the packet header, while DiffServ is a new protocol
and defines a new DS field, which replaces the eight-bit Type of Service (ToS) field in the IP header.
C
HAPTER

Quality of Service (QoS)

(Section 17.2 on page 170) to enable QoS on the P-79X, decide
(Section 17.3 on page
P-79X Series User's Guide
167
171) to set up classifiers to sort traffic into
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