Chapter 8 Wide Are Networking WAN

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Chapter 8Wide Are Networking (WAN)

• Concepts
• Packetizing
• Multiplexing
• Switching
• Transmissions
• Services
• Selection

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Packetizing

• Organize a group of bits in a predetermined
  structure format
• Include users data, overhead or management
  information for error-free transmission
• Packets, frames, cells, blocks, data units

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Multiplexing

• Frequency division multiplexing (FDM)
• Time division multiplexing (TDM)
• Statistical time division multiplexing (STDM)
• Wavelength division multiplexing (WDM)
• No interoperation between different manufacturers

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Frequency Division Multiplexing

• Use different frequencies for multiple input
  signals
• Use guardbands (take space, not efficiency)
• Transmit data and voice simultaneously over phone
  line
• Data over voice (DOV) unit with PBX for college
  campus, not for PSTN

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Time Division Multiplexing

• 100 bandwidth available for a portion of the
  time
• Use buffer memory central clock for flow
  control (polling)
• Composite message frame
• Simple, not efficiency

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Statistical Time Division Multiplexing

• Efficiency
• No idle time
• No padded blanks or null characters in composite
  message blocks
• Dynamically allocating time to terminals
• Higher cost
• Buffer
• Processing power for control information (source
  terminal, bytes of data, data compression)

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Wavelength Division Multiplexing

• Use different wavelengths of light
• Long-distance fiber optic network

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WAN Switching

• Packet switching network
• Circuit switching network

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Packet Switching

• Packet-switched network
• Public data network (PDN)
• Packet assembler/disassembler (PAD)
• Stand-alone devices
• Combined with modems or multiplexers
• Location end-user or entry point of packet
  switched data network
• Equipment DSEs (data-switching exchanges) or
  PSEs (packet-switching exchanges)
• Every user having the same transmission rate

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Packet Switched Services

• Connectionless
• Global address (source destination)
• Datagram (address with user data)
• Unreliable (no error detection or flow control)
• Connection-oriented virtual circuits
• Reliable packet network (ACK/NAK)
• Call set-up packets, message-bearing packets,
  clear request packet

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Circuit Switching

• Circuit switched network
• Use circuit without source destination address

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WAN Networking Transmission

• Local Loop
• Plain old telephone service (POTS)
• Integrated service digital network (ISDN)
• Asymmetric digital subscriber line (ADSL)
• Cable TV
• Boradband
• T1
• SONET

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ISDN

• A switched digital services for delivering voice,
  video, and data at same time
• Types
• Basic rate interface (BRI) 2BD ( 2 Bearer
  channels of 64 kbps 1 Delta or Data channel of
  16 kbps)
• Primary rate interface (PRI) 23BD
• Applications use ISDN terminal adapter
• Single user-to-office or Internet connection
• Office-to-office connection

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ADSL

• Use POTS at higher frequencies
• Use frequency division multiplexing (upstream
  downstream)
• Internet voice at same time
• Types
• Very high speed digital subscriber line (VDSL)
• Rate-adaptive digital subscriber line (RADSL)
• Symmetric digital subscriber line (SDSL)
• Application access Internet using POTS ADSL
  units

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Cable TV Problems for WAN

• Downstream only infrastructure
• Remedy methods
• Upstream using POTS
• Modify cable architecture to upstream downstream

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T-1

• High-capacity digital transmission over voice
  channel
• 1.544 Mbps bandwidth
• 24 64-Kbps channels (DS-0 circuit)
• T1 multiplexers
• Application
• Leased line or private line for business

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T-1 Digital Services

• Digital service hierarchy or DS standards
• DS-0 64Kbps
• DS-1 T-1uses four copper wires (two twisted
  pair)
• DS-2 T-2
• DS-3 T-3 uses optical fiber media
• DS-4 T-4

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SONET

• Optical transmission services
• For failure tolerance reliable data delivery
• Metropolitan area only
• Expensive
• Applications
• Broadband ISDN
• High-definition television

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WAN Services

• X.25
• Frame relay
• Switched multimegabit data service (SMDS)
• Cell relay - ATM
• Broadband ISDN

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X.25

• CCITT standard for the interface between DTE and
  packet-switched network
• Point-to-point error checking or hop-by-hop error
  checking
• Technology
• Packet assembler/disassembler (PAD)
• X.25 switches

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Frame Relay

• Error detection correction
• Point-to-point error detection (discard )
• End-to-end error correction
• Frame variable length
• Pro high through put with low delay for data
  only
• Con no guaranteed time delivery (not for voice
  video)

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Frame Relay

• Technology
• Frame relay or frame assembler/disassembler (FRAD
  or FAD) or frame relay access devices
• Frame relay switch
• Application inter-LAN traffic

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Switched Multimegabit Data Service - SMDS

• Connectionless network service
• Use SONET (T-3)
• Fixed-length cells of data
• Broadcast
• Only MCI for long distance

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Cell Relay - ATM

• Cell
• fixed length (53 octects)
• 48 for data and 5 for control information
• Predictable delivery time for voice and video
• Technology
• ATM network interface cards
• ATM hub
• ATM enterprise switch
• ATM gateway switches or ATM access switches
• ATM LAM emulation

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WAN Selection Criteria

• Data traffic patterns
• Business objectives

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Assignment

• Review chapter 8
• Read chapter 9