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Wireless Networking. Chapter 16. Objectives. Explain wireless networking standards Describe the process for implementing Wi-Fi networks Describe troubleshooting techniques for wireless networks. Overview. Introduction to Wireless Networking. Wireless network uses radio waves as the media

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Wireless Networking


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  1. Wireless Networking Chapter 16

  2. Objectives Explain wireless networking standards Describe the process for implementing Wi-Fi networks Describe troubleshooting techniques for wireless networks

  3. Overview

  4. Introduction to Wireless Networking • Wireless network uses radio waves as the media • Convenient and sometimes the only option • Same OSI layers as wired networks • Same upper-layer protocols as wired networks • Different methods for accessing the media • Wi-Fi IEEE 802.11 wireless Ethernet standards

  5. Three Parts to Chapter 16 • Wi-Fi Standards • Implementing Wi-Fi • Troubleshooting Wi-Fi

  6. Wi-Fi Standards

  7. Wi-Fi IEEE 802.11 Standards • 802.11a • 802.11b • 802.11g • 802.11n • Certified by 300-member Wi-Fi Alliance • Members design and manufacture Wi-Fi products • Certification should ensure compatibility

  8. 802.11 • Standards define how devices communicate • Some define how to secure communications • Each sub-standard by a IEEE subcommittee • Wireless Fidelity (Wi-Fi) • 802.11 established baseline features

  9. Hardware • Adapters • Wireless Ethernet NICS • PCI, PC Card, external USB • Wireless access point (WAP) • Basic WAP operates like a hub at Layer 1 • Often multiple devices in one box • High-speed hub or switch • Bridge • Router

  10. Figure 16.1 Wireless PCI NIC

  11. Figure 16.2 External USB wireless NIC

  12. Figure 16.3 Linksys device that acts as wireless access point, switch, and DSL router

  13. Software • Wireless device drivers • Wireless configuration utilities • Link state • Signal strength • Other settings • Wireless network modes • Security • Power-saving options

  14. Figure 16.4 Wireless client configuration utility

  15. Wireless Network Modes • Ad hoc mode • Also called peer-to-peer mode • Uses a mesh topology • Independent Basic Service Set (IBBS)

  16. Figure 16.5 Wireless ad hoc mode network

  17. Wireless Network Modes • Infrastructure mode • Uses one or more access points • Similar to a wired star topology • Basic service set (BSS) • Serviced by a single WAP • Extended service set (ESS) • Serviced by two or more WAPs

  18. Figure 16.6 Wireless infrastructure mode network

  19. Speed • Dependent on a few factors • Standard used by wireless devices • Distance • Interference • Dead spots

  20. Range • Hard to define • 802.11 “around 150 feet” • Affected by environmental factors

  21. Basic Service Set Identifier (BSSID) • Most basic infrastructure mode network • BSS is one WAP and one or more nodes • BSSID same as the MAC address of WAP • IBSS nodes (ad hoc mode) 48-bit string • BSSID in every packet

  22. Service Set Identifier (SSID) • Another level of naming • Standard name applied to BSS or IBSS • Sometimes called a network name

  23. Extended Service Set Identifier (ESSID) • Wi-Fi network with multiple WAPs (ESS) • Most Wi-Fi devices use term SSID

  24. Broadcasting Frequency • Potential for interference from other wireless devices • Tech must know frequencies of other wireless devices • Original 802.11 standards use 2.4-GHz frequency

  25. Broadcast Methods • Original IEEE 802.11 standard used spread-spectrum radio waves • Broadcasts data in small, discrete chunks • Used different frequencies within a range • Three different spread-spectrum broadcasting methods

  26. Direct-sequence spread-spectrum (DSSS) • Sends simultaneously on different frequencies • Early 802.11 standards used this • Uses ~22 MHz of bandwidth • Capable of greater data throughput than OFDM • More prone to interference than FHSS

  27. Frequency-hopping spread-spectrum (FHSS) • Hops from frequency to frequency • Sends on one frequency at a time • Uses less bandwidth than DSS (~1MHz)

  28. Orthogonal frequency-division multiplexing (OFDM) • Latest method • Combines multiple frequencies of DSSS with FHSS’s hopping capability • Later 802.11 standards use this

  29. Channels • A portion of the spectrum • 802.11 standard defined 14 channels • Different countries may limit channels • In U.S. WAP may use channels 1 – 11 • There is overlap • Do not use close channels on nearby WAPs • Most WAPs default to channel 1, 6, or 11

  30. CSMA/CA • Carrier sense multiple access/collision avoidance • Access method • Allows multiple devices to share network media • Wireless devices cannot detect collisions • Two collision avoidance methods • Distributed coordination function (DCF) • Point coordination Function (PCF)

  31. 802.11b • Data throughput up to 11 Mbps • Range up to 300 feet • Popular • 2.4-GHz frequency is crowded • More likely to have interference from other wireless devices

  32. 802.11a • Device on market after 802.11b • Different from all other 802.11 standards • 5-GHz frequency range • Up to 54 Mbps • Short range (~150 feet) • Never as popular as 802.11b • Incompatible with 802.11b

  33. Table 16.1 Table 16.2 Table 16.3 802.11 Summary 802.11b Summary 802.11a Summary Standard Frequency Spectrum Speed Range Compatibility 802.11 2.4GHz DSSS 11 Mbps ~300′ 802.11 Standard Frequency Spectrum Speed Range Compatibility 802.11b 2.4GHz DSSS 11 Mbps ~300′ 802.11b Standard Frequency Spectrum Speed Range Compatibility 802.11a 5.0GHz DSSS 11 Mbps ~150′ 802.11a

  34. 802.11g • Up to 54 Mbps • Range of 802.11b (~300 feet) • Backward compatible with 802.11b • WAP can service both 802.11b and 802.11g • All 802.11g network runs in native mode • Add 802.11b devices • Mixed mode • All communications drop to 11 Mbps max

  35. 802.11n • Faster and newer antenna technology • Most devices must use multiple antennae • Multiple in/multiple out (MIMO) • Up to 600 Mbps theoretically • Many WAPs use transmit beamforming • Dual-band WAPs run at 5 GHz and 2.4 GHz • Some WAPs support 802.11a devices

  36. Table 16.4 Table 16.5 802.11g Summary 802.11n Summary Standard Frequency Spectrum Speed Range Compatibility 802.11g 2.4GHz OFDM 54 Mbps ~300′ 802.11b/g • Standard Frequency Spectrum Speed Range Compatibility • 802.11n 2.4GHz1 OFDM 100+Mbps ~300′ 802.11b/g/n2 • Dual-band 802.11n devices can function simultaneously at both 2.4 and 5.0GHz bands. • Many dual-band 802.11n WAPs support 802.11a devices as well as 802.11b/g/n devices. This is not part of the standard, but something manufacturers have implemented.

  37. Wireless Networking Security • Problem • Easy-to-install devices have no default security • Network data packets are in radio waves • Three wireless security methods • MAC address filtering • Wireless authentication • Data Encryption

  38. MAC address filtering • Limits access to specific NICs • “Accepted users” list of MAC addresses • List stored in WAP • Rejects packets with other MAC addresses • Alternatively create exclusion list • Problem: hackers can spoof MAC addresses • MAC address must be updated for changes

  39. Wireless Authentication • Users with proper credentials get access • Can use a centralized security database • Requires extra steps for wireless users • 802.1X standard • RADIUS Server • Extensible Authentication Protocol (EAP) password encryption

  40. Wireless Authentication • RADIUS server • Provides authentication for network access • Enables access to user’s rights on network • Client computer is called a supplicant • WAP is the Network Access Server (NAS) • NAS contacts RADIUS server • RADIUS server checks security database • User given access if credentials are correct

  41. Figure 16.7 Authenticating using RADIUS

  42. Wireless authentication problem areas • Connection must be secure • PPP between supplicant and WAP/NAS • IPSec between WAP/NAS and RADIUS server • RADIUS server uses an authentication protocol • EAP-TLS • EAP-TTLS • PEAP • WAP and wireless NICs must use same authentication protocol

  43. Figure 16.8 Authentication using RADIUS with protocols in place

  44. Figure 16.9 Setting EAP authentication scheme

  45. Data Encryption • Wired Equivalent Privacy (WEP) • 64- or 128-bit encryption algorithm • Problems • Easily cracked • Only works on Data Link and Physical layers • No encryption above Data Link layer • Key is static and shared • No user authentication

  46. Data Encryption • Wi-Fi Protected Access (WPA) • Dynamic encryption key generation • Issued per-user and per-session • Temporal Key Integrity Protocol (TKIP) • 128-bit encryption key • Problem: key can be broken

  47. Data Encryption • Wi-Fi Protected Access 2 (WPA2) • Amendment of 802.11 standard by 802.11i • Issued per-user and per-session • Uses Advanced Encryption Standard (AES) • 128-bit block cipher • Not completely hack proof • Deters casual hackers

  48. Power over Ethernet (PoE) • Power and Ethernet signals via Ethernet ports • Good for WAPs far from power outlets • Both WAP and switch must comply with PoE

  49. Implementing Wi-Fi

  50. Site Survey • What wireless devices are already there? • Radio bands in use • Existing SSIDs and channels • Unique SSIDs • Separate channels within same radio band • Locate Interference Sources • Create sketch and identify interference sources • High-interference area may require 802.11n • May need multiple WAPs to avoid dead zones