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Appendix D
About Wireless LANs
Overview
Wireless networks have their own terms and jargon. It is necessary to understand many of
these terms in order to configure and operate a Wireless LAN.
Wireless LAN Terminology
Modes
Wireless LANs can work in either of two (2) modes:
•
Ad-hoc
•
Infrastructure
Ad-hoc Mode
Ad-hoc mode does not require an Access Point or a wired (Ethernet) LAN. Wireless Stations (e.g. note-
book PCs with wireless cards) communicate directly with each other.
Infrastructure Mode
In Infrastructure Mode, one or more Access Points are used to connect Wireless Stations (e.g. Notebook
PCs with wireless cards) to a wired (Ethernet) LAN. The Wireless Stations can then access all LAN re-
sources.
Access Points can only function in "Infrastructure" mode,
and can communicate only with Wireless Stations which are
set to "Infrastructure" mode.
SSID/ESSID
BSS/SSID
A group of Wireless Stations and a single Access Point, all using the same ID (SSID), form a Basic Ser-
vice Set (BSS).
Using the same SSID is essential. Devices with different SSIDs are unable to communicate with each
other. However, some Access Points allow connections from Wireless Stations which have their SSID
set to "any" or whose SSID is blank ( null ).
ESS/ESSID
A group of Wireless Stations, and multiple Access Points, all using the same ID (ESSID), form an Ex-
tended Service Set (ESS).
Different Access Points within an ESS can use different Channels. To reduce interference, it is recom-
mended that adjacent Access Points SHOULD use different channels.
As Wireless Stations are physically moved through the area covered by an ESS, they will automatically
change to the Access Point which has the least interference or best performance. This capability is
called Roaming. (Access Points do not have or require Roaming capabilities.)
D
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