Glossary
155
over layer 2 switched networks. It uses tag frames for
the prioritization scheme.
To be compliant with this standard, layer 2 switches
must be capable of grouping incoming LAN packets
into separate traffic classes.
802.1Q
IEEE 802.1Q is the
IEEE
standard for Virtual Local
Area Networks (
VLAN
s) specific to wireless
technologies. (See
http://www.ieee802.org/1/pages/
802.1Q.html
.)
The standard addresses the problem of how to break
large networks into smaller parts to prevent broadcast
and multicast data traffic from consuming more
bandwidth than is necessary. 802.11Q also provides
for better security between segments of internal
networks. The 802.1Q specification provides a
standard method for inserting VLAN membership
information into Ethernet frames.
A
Access Point
An access point is the communication hub for the
devices on a
WLAN
, providing a connection or
bridge between wireless and wired network devices.
It supports a
Wireless Networking Framework
called
Infrastructure Mode
.
When one access point is connected to a wired
network and supports a set of wireless stations, it is
referred to as a basic service set (
BSS
). An extended
service set (
ESS
) is created by combining two or
more BSSs.
Ad hoc Mode
Ad hoc mode is a
Wireless Networking Framework
in
which stations communicate directly with each other.
It is useful for quickly establishing a network in
situations where formal infrastructure is not required.
Ad hoc mode is also referred to as peer-to-peer mode
or an independent basic service set (
IBSS
).
AES
The Advanced Encryption Standard (AES) is a
symmetric 128-bit block data encryption technique
developed to replace DES encryption. AES works at
multiple network layers simultaneously.
Further information is available on the
NIST Web
site
.
B
Basic Rate Set
The basic rate set defines the transmission rates that
are mandatory for any station wanting to join this
wireless network. All stations must be able to receive
data at the rates listed in this set.
Beacon
Beacon frames provide the “heartbeat” of a
WLAN
,
announcing the existence of the network, and
enabling stations to establish and maintain
communications in an orderly fashion. It carries the
following information (some of which is optional):
•
The Timestamp is used by stations to update their
local clock, enabling synchronization among all
associated stations.
•
The Beacon interval defines the amount of time
between transmitting beacon frames. Before
entering power save mode, a station needs the
beacon interval to know when to wake up to
receive the beacon.
•
The Capability Information lists requirements of
stations that want to join the
WLAN
. For
example, it indicates that all stations must use
WEP
.
•
The Service Set Identifier (
SSID
).
•
The
Basic Rate Set
is a bitmap that lists the rates
that the
WLAN
supports.
•
The optional Parameter Sets indicates features of
the specific signaling methods in use (such as
frequency hopping spread spectrum, direct
