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Security of IEEE 802.11 Systems
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Bog'liq garg200721.7 Security of IEEE 802.11 Systems
The IEEE 802.11 provides for MAC access control and encryption mechanisms.
Earlier, the
wireline equivalent privacy
(WEP) algorithm was used to encrypt mes-
sages. WEP uses a Rivest Cipher 4 (RC4) pseudo-random number generator with
two key structures of 40 and 128 bits. Because of the inherent weaknesses of
the WEP, the IEEE 802.11i committee developed, a new encryption algorithm
(see Chapter 13) and worked on the enhanced security and authentication mecha-
nisms for 802.11 systems.
For access control, ESSID (also known as a WLAN service area ID) is pro-
grammed into each AP and is required knowledge in order for a wireless client to
associate with an AP. In addition, there is provision for a table of MAC addresses
called an
access control list
to be included in the AP, restricting access to stations
whose MAC addresses are not on the list.
Beyond layer 2, 802.11 WLANs support the same security standards
supported by other 802 LANs for access control (such as network operating
system logins) and encryption (such as IPSec or application-level encryption).
These higher-level technologies can be used to create end-to-end secure networks
encompassing both wired LAN and WLAN components, with the wireless piece
of the network gaining additional security from the IEEE 802.11i feature set.
21.8 Power
Management
Power management is necessary to minimize power requirements for battery
powered portable mobile units. The standard supports two power-utilization
modes, called
continuous aware mode
and
power save polling mode
. In the
former, the radio is always on and draws power, whereas in the latter, the radio is
dozing with the AP and is queuing any data for it.
A power saver mode or sleep mode is defi ned when the station is not
transmitting in order to save battery power. However, critical data transmissions
cannot be missed. Therefore APs are required to have buffers to queue messages.
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