ZyXEL Communications P-660N-T1A, User Manual

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P-660N-T1A User’s Guide
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14
Quality of Service (QoS)
14.1 Overview
Use the QoS screen 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.
In the following figure, your Internet connection has an upstream transmission
speed of 50 Mbps. You configure a classifier to assign the highest priority queue
(6) to VoIP traffic from the LAN interface, so that voice traffic would not get
delayed when there is network congestion. Traffic from the boss’s IP address
(192.168.1.23 for example) is mapped to queue 5. Traffic that does not match