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CWNA Chapter5

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  Chapter 5-802.11 standards ã  Alphabet Soup!  Exam Essentials ã Know the defined spread spectrum technologies of the srcinal 802.11 standard and the subsequent 802.11-2007 standard.    –  Although the srcinal 802.11 standard defend infrared, FHSS, and DSSS, later amendments that are now incorporated in the 802.11-2007 standard also define HR-DSSS, OFDM, and ERP. ã Remember both the required data rates and supported data rates of each PHY.    – DSSS and FHSS require and support data rates of 1 and 2 Mbps. Other PHYs offer a wider support for data rates. For example, OFDM and ERP-OFDM support data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbps, but only the rates of 6, 12 and 24 Mbps are mandatory. Please understand that data rates are speeds and not aggregate throughput. ã Know the frequency bands used by each PHY as defined by the 802.11-2007 standard .  – OFDM equipment operates in the 5 GHz UNII bands. DSSS, FHSS, HR-DSSS, and ERP devices transmit and receive in the 2.4 GHz ISM band. ã Explain the three vendor operational modes of ERP (802.11g) and the consequences of each mode.  –  An 802.11g access point may be configured as B-only mode, G-only mode, or B/G mixed mode. The three modes support different spread spectrum technologies and have different aggregate throughput results.  Exam Essentials ã Know the mandatory and optional technologies used in an ERP WLAN.    – ERP (802.11g) defines two mandatory PHYs, ERP-OFDM and ERP-DSSS/CCK. The two optional PHYs are ERP-PBCC and DSSS-OFDM. ã Define transmit power control and dynamic frequency selection.    – TPC and DFS are often mandated for use in the 5 GHz band. Both technologies are used as a means to avoid interference with radar transmissions. ã Explain the defined wireless security standards both pre-802.11i and post-802.11i.  – Before the passage of 802.11i, WEP encryption and either Open System or Shared Key authentication were defend. The 802.11i amendment calls for the use of CCMP/AES for encryption. For authentication, 802.11i defines either an 802.1X/EAP solution or the use of preshared keys.  Exam Essentials ã Define the Inter-Access Point Protocol and why it was srcinally proposed.  –IAPP is a “vendor interoperability” roaming protocol that is outlined in the 802.11F recommended practice. ã Explain the purpose of the 802.11e amendment and the medium access methods it requires.  – The 802.11e amendment addresses quality of service (QoS) issues by mandating the use of Enhanced Distributed Channel  Access (EDCA) and Hybrid Coordination Function (HCF). ã Understand the purpose of each 802.11 draft proposal.  – Each draft has a specific intended goal. The 802.11s draft, for example, outlines mesh networking. 802.11n proposes throughput enhancements using MIMO technology.
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