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Table Of Contents  CertiGuide to Security+
 9  Chapter 2:  Communication Security (Domain 2.0; 20%)
      9  2.6  Wireless

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2.6.1  WTLS
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2.6.3  WEP/WAP
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2.6.2  802.11x
(Page 1 of 2)

802.11 is really a family of wireless speeds and technologies, which CompTIA identifies with the term 802.11x. Be careful not to confuse this with 802.1X, covered in section 2.1.1. The first was plain 802.11 with no letter extension, which was released in 1997 with a data rate of 1 to 2Mbit. Two years later both 802.11a and 802.11b specifications were unveiled. The b version quickly caught on because of reasonable speed (11Mbit) at a price point far lower than 802.11a with a maximum throughput speed of 54Mbit. Later standards including 802.11g236 and 802.11i237, a security enhancement to 802.11, incorporated 802.1X authentication and improved encryption. 802.11n proposes 100Mbit/sec. 238 239

802.11x networks consist of one or more wireless access points (sometimes called “wired access points”), which act as “wireless hubs”, and one or more devices such as laptops or PDA’s with wireless network cards. Optionally, the wireless access points may be connected to a wired network as well.

[spacer]All Ethernet

While 802.11 are Ethernet, not all Ethernet is the same. Wired Ethernet uses collision detection, while 802.11 (wireless Ethernet) uses collision avoidance. This behavior difference is subtle but critical. In wired Ethernet (802.2, 802.3) if two data packets attempt to share the wire at the same time, the irresistible force meets the immovable object and they both die. That forces a resend of each packet (held back by a random time-out on each transmitting unit).

With 802.11, each wireless node broadcasts its intention to transmit telling the other nodes to wait their turn. This is great until one node cannot see the wireless signal due to interference. This is called the hidden node problem. The access point solves this by using the old serial protocol Request To Send/Clear To Send (RTS/CTS) and does not grant one of the nodes a CTS after the RTS.



 __________________

236. http://siliconvalley.internet.com/news/article.php/1472641

237. http://www.80211-planet.com/tutorials/article.php/1550561

238. http://www.nwfusion.com/details/6450.html?def

239. http://grouper.ieee.org/groups/802/11/Reports/highthroughput_update.html

Previous Topic/Section
2.6.1  WTLS
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2.6.3  WEP/WAP
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