Mac OS X Leopard - ARCAism

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CHAPTER 9 CONNECTING TO THE INTERNET
802.11a: 802.11a came out about the same time as 802.11b, provided faster transfer
speeds, and used radio frequencies in the 5 GHz range, which cut down on interference
from cordless phones, Bluetooth devices, and microwave ovens. However, 802.11a
products started shipping late by which time the industry was already implementing
802.11b. As such, 802.11a never really caught on to the extent of 802.11b. (An ironic
twist on this is that although Apple has never supported 802.11a, the current AirPort
chips included with Intel-based Macs do support 802.11a.) 802.11a is not compatible
with 802.11b or 802.11g.
802.11g: This is currently the most popular 802.11 variant. It is 100 percent compatible
with 802.11b, but when used with 802.11g devices at both ends, it provides much faster
transfer speeds and a slight boost in distance. Apple’s AirPort devices (both in computers
and base stations) quickly switched from 802.11b to 802.11g (Apple called this AirPort
Extreme). The downside with 802.11g is that it still operates in the crowded 2.4 to
2.5 GHz radio frequency range.
802.11n: 802.11n is the newest version of 802.11 with shipping products, even though the
actual specification has yet to be ratified. 802.11n increases transfer speeds about 45 and
25 the range over 802.11g, when used in 802.11n mode with other 802.11n devices. It can
work in either the 2.4 to 2.5 or 5.0 GHz radio frequency range. 802.11n devices also can
operate in three modes: Legacy, which supports 802.11 b/g and 802.11 a; Mixed, which
supports 802.11 b/g, 802.11 a, and 802.11n; and then a pure 802.11n mode, which is
necessary to take advantage of the increased speed and distances offered by 802.11n.
Apple’s newest AirPort Extremes as well as all new Core 2 Duo and newer Macs support
a draft of this technology.
Wi-Fi Security Schemes
Besides the different types of actual networks, there are also different security mechanisms used
to protect 802.11 networks. These include the following:
WEP: Wired Equivalent Privacy (WEP) was written as part of the 802.11 standard to
provide access control and data security to WLANs. Standard 64-bit WEP uses a 40-bit
encryption key; however, today 128-bit WEP is prevalent and supports a 104-bit
encryption key. Although WEP is quite popular and does provide at least some protection
from casual eavesdropping, from a security standpoint it is considered broken. Not only
are the keys vulnerable (a WEP key can be cracked in a few minutes using readily available
software from the Internet), but there are other inherent flaws in WEP that makes it
unsuitable for situations where security and data integrity are a priority.
WPA/WPA2: Wi-Fi Protected Access (WPA) was created in response to flaws discovered
with WEP, and it was quickly implemented and is based upon the IEEE 802.11i standard
(WPA2 fully implements 802.11i, while WPA implemented most of it). WPA uses an
improved encryption key, making cracking the key significantly more difficult than a
WEP key, and improves data integrity checks lacking in WEP. WPA2 further increases the
strength of the encryption key. WPA and WPA2 offer two modes of use: a Personal mode
and an Enterprise mode. Personal mode works similarly to WEP in that there is a single
preshared encryption key (PSK) used. In Enterprise mode a user must first log into a
RADIUS server that assigns a dynamic key to that user. Not only does this provide excellent
user access control, but by providing a unique key for each user, it provides excellent data
security as well.
802.1X: This is an IEEE standard that is part of the same group as 802.11 (though it is not
directly related). It is a method of authentication often used in conjunction with WPA2
Enterprise mode when authenticating the user to the RADIUS server.