Wireless Scalability
Wireless LANs (WLAN) are an extension to wired networks using wireless
standards, such as 802.11A/B/G. The 802.11 standards take the place of the
Ethernet standard, but both data-links support the same types of services.
The benefit of WLANs is that it allows users to relocate within the workspace,
closer to machinery or conference rooms, for instance.
WLAN QoS
802.11 wireless uses carrier sense multiple access/collision avoidance
(CSMA/CA), meaning transmissions are pre-announced, because systems
may not be able to hear each other or recognize collisions later. CA uses a
Distributed Coordination Function (DCF) to implement timers and delays to
ensure cooperation.
Unfortunately, DCF timers interfere with low-latency applications, such as
voice and video. Wi-Fi Multimedia (WMM or 802.11e) is an attempt to
shorten timers—proportional to Differentiated Services Code Point (DSCP)
priority—and prioritize important traffic. WMM replaces DCF with
enhanced DCF (EDCF) that creates four categories (platinum, gold, silver,
and bronze) and forces longer interframe waits on lower-priority traffic.