Bandwidth Management - ZyXEL Communications SBG5500-A User Manual

Bandwidth Management

11.1 Overview
Quality of Service (QoS) refers to both a network's ability to deliver data with minimum delay, and the
networking methods used to control the use of bandwidth. Without QoS, all traffic data is 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 application such as video-on-demand.
Configure QoS on the SBG to group and prioritize application traffic and fine-tune network
performance. Setting up QoS involves these steps:
Configure classifiers to sort traffic into different flows.
1
Assign priority and define actions to be performed for a classified traffic flow.
2
The SBG assigns each packet a priority and then queues the packet accordingly. Packets assigned a
high priority are processed more quickly than those with low priority 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.
This chapter contains information about configuring QoS and editing classifiers.
11.1.1 What You Can Do in this Chapter
• The General screen lets you enable or disable QoS and set the upstream bandwidth
page 196).
• The Queue Setup screen lets you configure QoS queue assignment
• The Classification Setup screen lets you add, edit or delete QoS classifiers
• The Policer Setup screen lets you add, edit or delete QoS policers
• The Shaper Setup screen lets you limit outgoing traffic transmission rate on the selected interface
(Section 11.6 on page
11.1.2 What You Need to Know
The following terms and concepts may help as you read through this chapter.
QoS versus Cos
QoS is used to prioritize source-to-destination traffic flows. All packets in the same flow are given the
same priority. CoS (class of service) 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.
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(Section 11.4 on page
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