ZyXEL Communications VMG3925-B10C, User Manual

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VMG3925-B10C/B30C User’s Guide
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HAPTER
10
Quality of Service (QoS)
10.1 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 VMG to group and prioritize application traffic and fine-tune network
performance. Setting up QoS involves these steps:
1
Configure classifiers to sort traffic into different flows.
2
Assign priority and define actions to be performed for a classified traffic flow.
The VMG 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.
10.1.1 What You Can Do in this Chapter
• The General screen lets you enable or disable QoS and set the upstream bandwidth ( Section 10.3 on
page 155 ).
• The Queue Setup screen lets you configure QoS queue assignment ( Section 10.4 on page 156 ).
• The Classification Setup screen lets you add, edit or delete QoS classifiers ( Section 10.5 on page 159 ).
• The Shaper Setup screen limits outgoing traffic transmission rate on the selected interface ( Section
10.6 on page 163 ).
• The Policer Setup screen to control incoming traffic transmission rate and bursts ( Section 10.7 on page
164 ).