3Com 3CRWEASYA73 / WL-575, User Manual, Page: 112 / 335

5-64
C
HAPTER
5: S
YSTEM
C
ONFIGURATION
C
ONFIGURING
W
I
-F
I
M
ULTIMEDIA
Wireless networks offer an equal opportunity for all devices to transmit data from
any type of application. Although this is acceptable for most applications,
multimedia applications (with audio and video) are particularly sensitive to the
delay and throughput variations that result from this equal opportunity wireless
access method. For multimedia applications to run well over a wireless network, a
Quality of Service (QoS) mechanism is required to prioritize traffic types and
provide an enhanced opportunity wireless access method.
The access point implements QoS using the Wi-Fi Multimedia (WMM) standard.
Using WMM, the access point is able to prioritize traffic and optimize
performance when multiple applications compete for wireless network
bandwidth at the same time. WMM employs techniques that are a subset of the
developing IEEE 802.11e QoS standard and it enables the access point to inter
operate with both WMMenabled clients and other devices that may lack any
WMM functionality.
Access Categories – WMM defines four access categories (ACs): voice, video, best
effort, and background. These categories correspond to traffic priority levels and
are mapped to IEEE 802.1D priority tags. The direct mapping of the four ACs to
802.1D priorities is specifically intended to facilitate inter operability with other
wired network QoS policies. While the four ACs are specified for specific types of
traffic, WMM allows the priority levels to be configured to match any
network-wide QoS policy. WMM also specifies a protocol that access points can
use to communicate the configured traffic priority levels to QoS-enabled wireless
clients.
Table 3 WMM Access Categories
WMM Access Categories
Access
Category WMM
Designation
Description
802.1D
Tags
AC_VO (AC3) Voice
Highest priority, minimum delay.
Time-sensitive data such as VoIP (Voice
over IP) calls.
7, 6
AC_VI (AC2) Video
High priority, minimum delay.
Time-sensitive data such as streaming
video.
5, 4