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Wireless Networks

Wireless Networks

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Wireless Networks

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  1. Wireless Networks Tamus, Zoltán Ádám zoltanadam_tamus@yahoo.com http://adaminf.atw.hu

  2. Basics of Communication • Transmitter(coding)->Channel->(decoding) Receiver

  3. The Radio-Channel • Wireless technologies use electromagnetic waves as channel • Radiowaves (freq. 30 kHz-30 GHz) • Light (Infra Red) (wavelength ~900 nm)

  4. Personal Area Networks • Interconnecting devices without wire • Headsets • Notebooks • PDA (Personal Digital Assistant) • Mobile phones • GPS • Peripherals (Keyboard, Mouse, Printer, Game controller etc.)

  5. Personal Area Networks • Bluetooth • 1998, Special Interest Group (Ericsson, IBM, Intel, Nokia, Toshiba) • Uses radiofrequency: in the 2.4 GHz band, frequency hopping spread spectrum system • Max. 1 Mb/sec bandwidth • Operating range ~10 m, but in high power applications can be extended to 100 m

  6. Personal Area Network • Bluetooth devices

  7. Personal Area Network • IrDA (Infrared Data Association) 1993 • Use Infrared light • Operating range max. 1 m • Bandwidth: 4 Mb/sec.

  8. Local Area Networks • Home • Offices • Public WLAN, Wi-Fi Hot Spots • Hotels • Airports • Net Cafes http://www.wi-fihotspotlist.com/http://www.hotspotter.hu/en/ • Ad Hoc peer to peer

  9. Local Area Network • Typical WLAN application in home or small office

  10. Local Area Network • Network Access in Buildings • Desktop PCs • Notebooks • PDAs

  11. Local Area Networks • IEEE 802.11 standard • 802.11a • 1999 • 5 GHz band • Max. 54 Mb/sec • 802.11b • 2.5 GHz • Max. 11 Mb/sec • 802.11g • 2.5 GHz • Max. 54 Mb/sec

  12. Security • Eavesdropping & Espionage • Wireless technologies use radio waves. Eavesdroppers can easily pick up unencrypted messages by listening the ether • Rouge Access Points • An employee of an organization might hook up an access point without the permission or even knowledge of IT.

  13. Security • Accidental Associations • A wireless network is setup using the same SSID as your network and within range of your wireless device. Connecting to another wireless LAN can divulge passwords or sensitive document to anyone on the neighbouring network • Denial of Service • Flowing packages to the network take the resources • RF interference with an external transmitter

  14. Security • Securing Wireless Networks • WEP (Wired Equivalent Privacy) • Problems: Easily vulnerable because of the permanent keys and the short initialization vector • WPA (Wi-Fi Protocol Access) • The clients use periodically changed different keys • VPN (Virtual Private Network)

  15. Security • Authentication • SSID (Service Set Identifier) • Weakness in IEEE 802.11: the SSID is sent without encrypting! • MAC address filtering • MAC (Media Access Control) • WEP not encodes the MAC field of the frame!

  16. Setting up a wireless router • Connection to the broadband router • Connecting a PC

  17. Configuration • Access to Web-based utility software by Router’s IP address • User Name: <blank> • Password: admin

  18. Setting up Internet Connection • DHCP • Static IP • PPPoE • PPTP

  19. Setting up Wireless Network • Mode: B/G • SSID Broadcasting ? • Channel

  20. Security Settings • WEP • Level of WEP encryption: 64-bit or 128-bit

  21. Security Settings • WPA • WPA2 • WPA2 Mixed • Set the Passphrase and Renewal period

  22. Access control • MAC address filtering

  23. Security Precautions • Change the default SSID. • Disable SSID Broadcast. • Change the default password for the Administrator account. • Enable MAC Address Filtering. • Change the SSID periodically. • Use the highest encryption algorithm possible. Use WPA if it is available. Please note that this may reduce your network performance. • Change the WEP encryption keys periodically.