Wireless Networking

Wireless Problem Discovery and Solutions

Module-12

Jerry BernardiniCommunity College of Rhode Island

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Presentation Reference Material

• CWNA Certified Wireless Network Administration Official Study Guide, Fourth Edition, Tom Carpenter, Joel Barrett– Chapter-11, page 529-572

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WLAN Analysis Systems

• Handheld Protocol Analyzers• Laptop Protocol Analyzers• Basic Protocol Analyzers• Handheld RF Spectrum Analyzers• Laptop RF Spectrum Analyzers• Wireless Intrusion Detection Systems• Wireless Intrusion Prevention Systems• Distributed RF Spectrum Analyzers

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Handheld Protocol Analyzers

• PDA-Based – Convenient – Low processing power and small screen– Medium cost ($1000)– PocketPC based applications– WiFi PPC, CommView, MiniStumbler, TamoSoft

• Integrated – Specialized– Powerful – Full featured– High cost ($10,000 to $25,000)– Fluke OptiView Integrated Network Analyzer

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Laptop Protocol Analyzers

• Large choice of applications– Wireshark (PC and Linux)– Wildpackets Omnipeek– AirMagnet– Others

• Wireless adapter Driver Issues– Applications only work with certain adapters– Obtain application first– Download the needed drivers

• Adapter Choices– PCMCIA– ExpressCard– USB

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Cheep Way to View RF and Stations in Area

WiFi Hopper

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Website: http://wifihopper.com/overview.html

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Spectrum Analyzers

• Scan radio frequency spectrum and provides graphical display of results– Typically measure signal-to-noise ratio– Single-frequency analyzers measure signal-to-noise ratio at specified

frequency– Helpful in identifying interference problems

• Thus, helps properly position/orient AP

• Costly $500 $50,000

Handheld RF Spectrum Analyzers

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Handheld RF Spectrum Analyzers –Expensive

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Frequency range: 100kHz - 6 GHz.Internal preamplifier with frequency range from 100 kHz - 6 GHz.Displayed average noise level typ. -135 dBm (RBW 100 Hz).0.5 dB typ. level accuracy up to 6 GHz.Resolution bandwidths 100 Hz - 1 MHz, 1 and 3 steps.Wide range of detectors; sample, max/min peak, auto peak, RMS.

Cost: $13,500

NSF Grant 0202396

Other Spectrum Analyzers

2.0 5.0Frequency, f (GHz)

Two basic types:Hardware and Software

Laptop RF Spectrum Analyzers

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•Fluke•Cisco•Other•Cognio (now owned by Cisco)

Wireless Intrusion Detection Systems

• Cisco

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Intrusion Detection System

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Wireless Security Articles

• http://www.windowsecurity.com/articles_tutorials/intrusion_detection/

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Distributed RF Spectrum Analyzers

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Case Study 1 FIGURE 11.29 Filter configuration in CommView for Wi-Fi

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Case Study 2 FIGURE 11.30 Filtered capture in CommView for Wi-Fi

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Case Study 2 FIGURE 11.31 Two file transfers at different data rates

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Case Study 2 FIGURE 11.32 Captured frames from the shipping department’s access point

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Case Study 2 FIGURE 11.33 Captured wired frames between the engineering access point and the RADIUS

server

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Case Study 3 FIGURE 11.34 Protocol analyzer showing the low RF medium usage

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Case Study 3 FIGURE 11.35 Abnormally high retransmission count

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Case Study 3 FIGURE 11.36 Spectrum analyzer showing narrowband RF interference

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