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DSL – ADSL and Wi - Fi

DSL – ADSL and Wi - Fi. DSL ADSL Protocols Security Wi-Fi Cable vs ADSL. DSL History. Dial Up too slow Pay for the connection time Telephone occupied VLSI advancements ( 1990 ) DSLAM ( DSL Access Multiplexer ) DSL modem cheaper Deployed over existing cable

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DSL – ADSL and Wi - Fi

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  1. DSL – ADSL and Wi - Fi DSL ADSL Protocols Security Wi-Fi Cable vs ADSL

  2. DSL History • Dial Up too slow • Pay for the connection time • Telephone occupied • VLSI advancements ( 1990 ) • DSLAM ( DSL Access Multiplexer ) • DSL modem cheaper • Deployed over existing cable • Installing Fiber Optic Cable expensive • Competition in DSL drop prices

  3. What is DSL ? • Digital Subscriber Line • Splitter ( Client ) • Splitter ( Service Provider) • DSLAM • Fast Network Connection ( Fiber Optic ) • Switch • PSTN (Public Switched Telephone Network )

  4. ADSL Frequencies

  5. ADSL • Asymetric Digital Subscriber Line • Asymetric -> Downstream != Upstream • 1 * Downstream = 4 * Upstream

  6. How does it work? • Upstream / Downstream bands • 25.875 kHz to 138 kHz Upstream • 138 kHz – 1104 kHz Downstream • 4.3125 kHz pieces ( 26 – 224 ) • Acceptable signal-to-noise ratio • Distance – Electrical Noise • Splitter • DSLAM • PSTN

  7. DSL

  8. DSLAM

  9. xDSL • High Data Rate DSL (HDSL) • Symetric DSL (SDSL) • Asymetric DSL (ADSL) • Rate – Adaptive DSL (RADSL) • Very-high-bit-rate DSL (VDSL) • Very-high-bit-rate DSL2 (VDSL2) • Symetric High-speed DSL (G.SHDSL) • Powerline DSL (PDSL)

  10. Speed Dependencies • ADSL – 5km, 128kbps / 8mbps • ADSL2 – 2.5km, 12mbps ( Framing – Err. Corr) • ADSL2+ - 1.5, 24mbps ( 2.2 MHz )

  11. Protocols • PPPoE • DHCP • Bridging • Transparent Bridging • Source Route Bridging

  12. PPPoE • Point to Point Protocol over Ethernet • PPP -> Dial Up • Encapsulate PPP frames in Ethernet frames • Clasical connection • Username • Password • IP assaign -> Connection Open • Reuse of IP

  13. DHCP • Dynamic Host Configuration Protocol • Request and obtain internet address • DHCP client -> Query -> DHCP server • Immediately after Booting • IP address • Subnet Mask • DNS server ( Domain Name System Server ) • Default Gateway info.

  14. DHCP

  15. Network Bridge • Network Switch • Broadcast Message • Transparent Bridging • Forwarding Database • Recieved Frames Addresses • Broadcast Message • Store route in D.B.

  16. Network Bridge • Source Route Bridging • Single Route frames (SR) • Fixed destinations • All Route frames (AR) • Find routes • Broadcast frame -> All Ports • Register each step • Max. Hop Count • Diameter of Network Graph • Decrement by each Bridge • Hop Count = 0 -> Discard • First AR frame -> Best Route • Others Discarded

  17. ADSL MODEM • What is it? • Routing • Security • Firewall • NAT service • Wireless Connection

  18. ADSL Modem

  19. Wi-Fi • SSID (Service Set Identifier) • Broadcast SSID • Beacon packets • 100 ms • Same SSID -> Signal Strength • Lowest 1 Mbit/s

  20. Wireless Protocols

  21. Wireless Security • Access Control • MAC address check • Allow • Ban • WEP • WPA • 802.1x

  22. Access Control

  23. WEP(WiredEqivalentPrivacy) • IEEE 802.11 standard • RC4 • Stream Cipher • Block Cipher ? • RC4 for confidentiality • CRC-32 checksum for integrity

  24. WEP(WiredEqivalentPrivacy) • 64 BIT WEP – 40 BIT Hex – 4 * 10 = 40 • 128 BIT WEP – 104 BIT Hex – 4 * 26 = 104 • 256 BIT WEP – 232 BIT Hex – 4 * 58 = 232 • + 24 BIT Initialazition Vector (block of BIT exe S.C. Or B.C) • Stream Chiper • Block Cipher • =WEP key

  25. WEP

  26. Wi-Fi Protected Access (WPA) • Key Recovery Attacks on WEP • Keys unknown but • Mathematical relation between keys known • TemporalKeyIntegrityProtocol ( TKIP ) • Per-packet key mixing • a message integrity check and • re-keying mechanism • Every data packet -> unique encryption key. • Message Integrity Check • MAC address genereated

  27. TKIP

  28. WPA

  29. 802.1x • Data – Link Layer • Closed Wireless Access Points • Detection -> Port on switch Unauthorized • Authenticator -> EAP Request -> Supplicant • Supplicant -> EAP Response -> Authenticator • Authenticator -> EAP Responce -> Authentication Server • EAP Logoff • Port Unauthorized

  30. 802.1x

  31. 802.1x

  32. Cable vs ADSL • SPEED • Cable upto 2 times faster than ADSL ( 3.0Mbps – 1.5Mbps) • Shared bandwidth • SHARING AND SECURITY • Cable modem -> Pay for each extra client • ADSL -> No Limitations • Both very secure

  33. Cable vs ADSL • Price

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