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Chapter 5-802.11 standards

Chapter 5-802.11 standards. Alphabet Soup!. Exam Essentials. Know the defined spread spectrum technologies of the original 802.11 standard and the subsequent 802.11-2007 standard.

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Chapter 5-802.11 standards

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  1. Chapter 5-802.11 standards • Alphabet Soup!

  2. Exam Essentials • Know the defined spread spectrum technologies of the original 802.11 standard and the subsequent 802.11-2007 standard. • Although the original 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. • 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. • 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. • 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.

  3. Exam Essentials • 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. • 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. • 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.

  4. Exam Essentials • Define the Inter-Access Point Protocol and why it was originally proposed. • IAPP is a “vendor interoperability” roaming protocol that is outlined in the 802.11F recommended practice. • 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). • 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.

  5. Overview of IEEE 802.11 • 802.11 task group and subcommittees • Revising and amending the MAC and PHY standards • Media Access • Physical • Draft standards are not official yet • Sometimes they are adopted by vendors as pre 802.11x Pg 155

  6. Overview of IEEE 802.11 • Two sets of definitions • The original alphabet soup • The 802.11-2007 and clauses • Need to know the technologies, clauses, and letters • 802.11 original in 1997 • Also known as 802.11 Prime Pg 155

  7. Overview of IEEE 802.11 • 802.11-2007 rolled up ratified amendments • IEEE Std 802.11-1999 (R2003) • IEEE Std 802.11a-1999 • IEEE Std 802.11b-1999 • IEEE Std 802.11d-2001 • IEEE Std 802.11g-2003 • IEEE Std 802.11h-2003 • IEEE Std 802.11i-2004 • IEEE Std 802.11j-2004 • IEEE Std 802.11e-2005 Pg 155

  8. Overview of IEEE 802.11 • Original Physical layer options • Infrared (IR) • Infrared (IR) technology uses a light-based medium. Although an infrared medium was indeed defined in the original 802.11 standard, the implementation is obsolete. More information about modern implementations of infrared technology can be found at the Infrared Data Association’s website, at www. irda. org. The scope of this book focuses on the 802.11 RF mediums. Infrared devices are known as clause 16 devices. • Frequency hopping spread spectrum (FHSS) • Radio frequency signals can be defined as narrowband signals or as spread spectrum signals. An RF signal is considered spread spectrum when the bandwidth is wider than what is required to carry the data. Clause 14 • Direct sequence spread spectrum (DSSS) • Direct sequence spread spectrum (DSSS) is another spread spectrum technology that is frequently used and easiest to implement. DSSS 802.11 radio cards are often known as clause 15 devices. Pg 155

  9. 802.11Prime • FHSS and DSS were originally specified for 2.4 Ghz ISM band • 2.4 Ghz to 2.4835 Ghz • Older equipment is much less common now • DSS cannot work with FHSS • Most early implementations were FHSS • Original speeds were 1 Mbps or 2 Mbps • This is bandwidth, not throughput • Used Barker Keying Pg 156

  10. 802.11 Ratified Amendments • 802.11 b • 802.11 a • 802.11 g • 802.11d • 802.11 F • 802.11 h • 802.11 I • 802.11 j • 802.11 e • 802.11 k • 802.11 r Pg 157

  11. 802.11 b • HR-DSSS • Backward compatible with any DSSS implementations of 802.11 prime • Not common • Clause 18 • 2.4 Ghz • CCK modulation • 1, 2, 5.5, 11 Mbps • 5.5 and 11 are HR-DSSS Pg 157

  12. 802.11 a • For the new 5 Ghz UNII band • Less crowded than 2.4 Ghz • Clause 17 • Orthogonal Frequency Division Multiplexing (OFDM) • Required rates • 6, 12, 24 • Also supports • 6, 9, 12, 18, 24, 36, 48, 54 • Different vendors can choose different implementations • Not compatible with earlier standards • But can coexist because no overlap Pg 159

  13. 802.11 g • Clause 19 • 2.4 Ghz • Extended Rate Physical-ERP • Enhance the 802.11b speeds • Two PHY • ERP-OFDM • ERP-DSSS/CCK • Backward compatible with 802.11b OFDM Pg 160

  14. 802.11 g • Required Speeds • 6, 12, 24 • For backward compatibility, ERP-DSSS/CCK supports 1, 2, 5.5, 11 • Optional • 6, 9, 12, 18, 24, 36, 48, 54 • Also had ERP-PBCC and DSS-OFDM • Not used much Pg 160

  15. 802.11 g • Due to backward compatibility, multiple implementations • B-only mode • G-Only Mode • b/g mode • Supports both, but when a 802.11b signal is detected, all stations are forced to protection • Causes degradation of throughput to support older rates Pg 160

  16. 802.11 Amendments Pg 162

  17. Other Amendments • 802.11 d • To support other countries • Beacon and probes to support country specific power levels • 802.11 F • Recommended practice • Roaming standard • Like cell phones • IAPP is now a recommendation • Intervendor roaming isn’t great Pg 163

  18. Roaming

  19. Roaming

  20. Inter Access Point Protocol (IAPP) • Recommended practice • Never specified how to implement in 802.11 • 802.11F never ratified • If vendors support IAPP, you should be able to roam between vendors Pg 164

  21. 802.11 h • The dynamic frequency selection (DFS) service provides for the following: • An AP will allow client stations to associate based on the supported channel of the access point. The term associate means that a station has become a member of the AP’s wireless network. • An AP can quiet a channel to test for the presence of radar. • An AP may test a channel for the presence of radar before using the channel. • An AP can detect radar on the current channel and other channels. • An AP can cease operations after radar detection to avoid interference. • When interference is detected, the AP may choose a different channel to transmit on and inform all the associated stations. Pg 166

  22. 802.11 h • TPC provides • Designation of the maximum transmit power levels permitted on a channel, as permitted by regulations. • An AP can specify the transmit power of any or all stations that are associated with the access point. • An AP can change transmission power on stations based on factors of the physical RF environment such as path loss. Pg 167

  23. 802.11 i • Data privacy • Authentication • Replaced WEP • WEP was a poorly implemented solution Pg 167

  24. Wireless Security • Open System Authentication • Verified identity regardless • No authentication • Shared Key Authentication • If you had the key, you were authenticated Pg 168

  25. 802.11 i • Defined the Robust Security Network (RSN) • Better hide data broadcast on an unbounded medium • Bigger guard at the door to the network • Data Privacy • Authentication Pg 168

  26. 802.11 i-Data Privacy • Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (CCMP) • Advanced Encryption Standard (AES) algorithm • AES/CCMP or CCMP • Also supports Temporal Key Integrity Protocol with RC-4 stream cipher • More like WEP, but much better Pg 168

  27. 802.11 i-Authentication • 802.1X • Implements Extensible Authentication Protocol (EAP) • Method of authentication not specified • Commonly used with existing authentication systems • RADIUS • KERBEROS • Pre-Shared Key • Uses a passphrase/Key as the starting point Pg 168

  28. 802.11 i-Robust Security Network • Defines the methods for establishing authentication, negitiating security and generating keys • WiFi Alliance-WPA2 matches the 802.11i Pg 168

  29. 802.11 j • Japanese Market approval • Different frequencies and bands Pg 168

  30. 802.11 e • Layer 2 MAC methods for providing QOS for time sensitive applications • Voice Over technologies • 802.11 prime had some methods for controlling network • Distributed Coordination Function (DCF) • Random • Point Coordination Function • Access point takes control and polls clients Pg 169

  31. 802.11 e • 802.11e defines Hybrid Coordination Function (HCF) • Enhanced Distributed Channel Access (EDCA) • Extends DCF-allows for prioritization of frames • Create an EZ-PASS lane for higher need traffic • Hybrid Coordination Function Controlled Channel Access (HCCA) extends PCF • Allows AP to allow certain stations to transmit first • Matches to the WiFi Alliance Wi-Fi Multimedia (WMM) Pg 169

  32. 802.11 k • Radio Resource Measurements • Ability to gather information about the network for better control • Layer 1 and Layer 2 • Data gathered by stations and processed by AP or WLAN controller • Transmit power control (TPC) • The 802.11h amendment defined the use of TPC for the 5 GHz band to reduce interference. Under 802.11k, TPC will also be used in other frequency bands and in areas governed by other regulatory agencies. • Client statistics • Physical layer information such as signal-to-noise ratio, signal strength, and data rates can all be reported back to the access point or WLAN controller. MAC information such as frame transmissions, retries, and errors may all be reported back to the access point or WLAN controller as well. Pg 170

  33. 802.11 k • Channel statistics • Clients may gather noise-floor information based on any RF energy in the background of the channel and report this information back to the access point. Channel load information may also be collected and sent to the AP. The access point or WLAN controller may use this information for channel management decisions. • Neighbor reports • Mobile Assisted Handover (MAHO) is a technique used by digital phones and cellular systems working together to provide better handover between cells. 802.11k gives access points or WLAN controllers the ability to direct stations to perform the sort of tasks that a cellular network requires its handhelds to do when using MAHO. • Clients will keep table of access points and make decisions on when to roam Pg 170

  34. 802.11 r • Fast basic service set transition • Fast secure roaming • Proposed for VoIP and other real time applications • Needed because security takes extra time • Since Authentication takes time, 802.11 r manages authentication before doing the switch between access points to limit delay. • Not part of the 802.11 2007 Pg 171

  35. 802.11 Draft Amendments • Test is focused on 802.11n, which is now a standard Pg 171

  36. 802.11 n • 2.4 Ghz AND 5 Ghz • High Throughput-HT • Both PHY and MAC enhanced for 100 Mbps • MIMO technology with OFDM • Increased throughput and greater range Pg 172

  37. 802.11 Draft Amendments • 802.11 m • housekeeping • 802.11 n • New HT standard • 802.11 p • Wireless Access in Vehicles • 802.11 s • Wireless Distribution System-Mesh Networks • 802.11 T • metrics Pg 172

  38. 802.11 Draft Amendments • 802.11 u • Internetworking to other standards • 802.11 v • Wireless centralized control • 802.11 w • Secure management frames • 802.11 y • New frequencies • 802.11 z • Direct Link Setup • 802.11 aa • Robust audio and video streaming Pg 175

  39. Exam Essentials • Know the defined spread spectrum technologies of the original 802.11 standard and the subsequent 802.11-2007 standard. • Although the original 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. • 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. • 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. • 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.

  40. Exam Essentials • 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. • 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. • 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.

  41. Exam Essentials • Define the Inter-Access Point Protocol and why it was originally proposed. • IAPP is a “vendor interoperability” roaming protocol that is outlined in the 802.11F recommended practice. • 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). • 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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