ZyXEL Communications NWA-3100, Руководство пользователя

Страница: 69 / 294

Chapter 5 Wireless Configuration
ZyXEL NWA-3100 User’s Guide
69
5.3 Quality of Service
This section discusses the Quality of Service (QoS) features available on the ZyXEL Device.
5.3.1 WMM QoS
WMM (Wi-Fi MultiMedia) QoS (Quality of Service) ensures quality of service in wireless
networks. It controls WLAN transmission priority on packets to be sent over the wireless
network.
WMM QoS prioritizes wireless traffic according to the delivery requirements of the individual
and applications. WMM QoS is a part of the IEEE 802.11e QoS enhancement to certified Wi-
Fi wireless networks.
On APs without WMM QoS, all traffic streams are given the same access priority to the
wireless network. If the introduction of another traffic stream creates a data transmission
demand that exceeds the current network capacity, then the new traffic stream reduces the
throughput of the other traffic streams.
The ZyXEL Device uses WMM QoS to prioritize traffic streams according to the VLAN or
DSCP information in each packet’s header. The ZyXEL Device automatically determines the
priority to use for an individual traffic stream. This prevents reductions in data transmission
for applications that are sensitive to latency (delay) and jitter (variations in delay).
5.3.1.1 WMM QoS Priorities
The following table describes the WMM QoS priority levels that the ZyXEL Device uses.
5.3.2 ATC
Automatic Traffic Classifier (ATC) is a bandwidth management tool that prioritizes data
packets sent across the network. ATC 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 and a low
level of jitter such as Voice over IP or Internet gaming, and those for which jitter alone is a
problem such as Internet radio or streaming video.
Table 8 WMM QoS Priorities
PRIORITY LEVEL DESCRIPTION
voice
(WMM_VOICE) Typically used for traffic that is especially sensitive to jitter. Use this priority
to reduce latency for improved voice quality.
video
(WMM_VIDEO) Typically used for traffic which has some tolerance for jitter but needs to be
prioritized over other data traffic.
best effort
(WMM_BEST_EFFORT) Typically used for traffic from applications or devices that lack QoS
capabilities. Use best effort priority for traffic that is less sensitive to latency,
but is affected by long delays, such as Internet surfing.
background
(WMM_BACKGROUND) This is typically used for non-critical traffic such as bulk transfers and print
jobs that are allowed but that should not affect other applications and users.
Use background priority for applications that do not have strict latency and
throughput requirements.