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Communication Security: Wireless • Chapter 4 179

and 2 Mbps and generally have a range of approximately 300 feet. Because of the
need for higher rates of data transmission and to provide more functionality at the
MAC layer, the 802.11 Task Group developed other standards. (In some cases the
802.11 standards were developed from technologies that preceded them.)
The IEEE 802.11 standard provides for all the necessary definitions and con-
structs for wireless networks. Everything from the physical transmission specifica-
tions to the authentication negotiation is defined by this standard.Wireless traffic,
like its wired counterpart, consists of frames transmitted from one station to
another.The primary feature that sets wireless networks apart from wired networks
is that at least one end of the communication pair is either a wireless client or a
wireless AP.
IEEE 802.11b

The most common standard used today for wireless networks, the IEEE 802.11b
standard defines DSSS networks that use the 2.4 GHz ISM band and communicate
at speeds of 1, 2, 5.5, and 11 Mbps.The 802.11b standard defines the operation of
only DSSS devices and is backward compatible with 802.11 DSSS devices.The
standard is also concerned only with the PHY and MAC layers: Layer 3 and higher
protocols are considered payload.There is only one frame type used by 802.11b
networks, and it is significantly different from Ethernet frames.The 802.11b frame
type has a maximum length of 2346 bytes, although it is often fragmented at 1518
bytes as it traverses an AP to communicate with Ethernet networks.The frame type
provides for three general categories of frames: management, control, and data. In
general, the frame type provides methods for wireless devices to discover, associate
(or disassociate), and authenticate with one another; to shift data rates as signals
become stronger or weaker; to conserve power by going into sleep mode; to handle
collisions and fragmentation; and to enable encryption through WEP. Regarding
WEP, it should be noted that the standard defines the use of only 64-bit (also
sometimes referred to as 40-bit to add to the confusion) encryption, which may
cause issues of interoperability between devices from different vendors that use
128-bit or higher encryption.

EXAM WARNING
Remember that IEEE 802.11b functions at 11 Mbps.

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