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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

DSL – ADSL and Wi - Fi

DSL

ADSL

Protocols

Security

Wi-Fi

Cable vs ADSL

dsl history
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
what is dsl
What is DSL ?
  • Digital Subscriber Line
  • Splitter ( Client )
  • Splitter ( Service Provider)
  • DSLAM
    • Fast Network Connection ( Fiber Optic )
    • Switch
      • PSTN (Public Switched Telephone Network )
slide5
ADSL
  • Asymetric Digital Subscriber Line
  • Asymetric -> Downstream != Upstream
  • 1 * Downstream = 4 * Upstream
how does it work
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
slide9
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)
speed dependencies
Speed Dependencies
  • ADSL – 5km, 128kbps / 8mbps
  • ADSL2 – 2.5km, 12mbps ( Framing – Err. Corr)
  • ADSL2+ - 1.5, 24mbps ( 2.2 MHz )
protocols
Protocols
  • PPPoE
  • DHCP
  • Bridging
    • Transparent Bridging
    • Source Route Bridging
pppoe
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
slide13
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.
network bridge
Network Bridge
  • Network Switch
  • Broadcast Message
  • Transparent Bridging
    • Forwarding Database
      • Recieved Frames Addresses
    • Broadcast Message
    • Store route in D.B.
network bridge1
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
adsl modem
ADSL MODEM
  • What is it?
  • Routing
  • Security
    • Firewall
    • NAT service
  • Wireless Connection
wi fi
Wi-Fi
  • SSID (Service Set Identifier)
  • Broadcast SSID
  • Beacon packets
  • 100 ms
  • Same SSID -> Signal Strength
  • Lowest 1 Mbit/s
wireless security
Wireless Security
  • Access Control
    • MAC address check
    • Allow
    • Ban
  • WEP
  • WPA
  • 802.1x
wep w ired e qivalent p rivacy
WEP(WiredEqivalentPrivacy)
  • IEEE 802.11 standard
  • RC4
    • Stream Cipher
    • Block Cipher ?
  • RC4 for confidentiality
  • CRC-32 checksum for integrity
wep w ired e qivalent p rivacy1
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
wi fi protected access wpa
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
802 1x
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
cable vs adsl
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
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