Wide Area Networks

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Wide Area Networks

• CS 363
• DePaul University

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Questions on Final?
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Group Evaluations

• 25 points per group member, including yourself
• Distribute total number of points across group
  members as you see fit
• Hand in now

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Wide Area Networks

• Definedgt
• Transmission strategies
• PSTN
• Leased circuits
• Fiber
• Microwave/Satellite
• Wireless
• Internet

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Metropolitan Area Networks
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WANS

• Enterprise Networks
• DePauls network
• Global Networks
• The Internet

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PSTN Connectivity

• Circuits come in from CO
• Connect at Demarc in building
• Provide following services

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PSTN Services

• Switched 56
• X.25
• T1
• T3
• Frame Relay
• SMDS
• ISDN
• ATM

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PPP

• multiprotocol
• negotiates and registers IP assignments on
  dial-up
• negotiates header compression
• relatively good security

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SLIP

• only TCP/IP
• requires manual IP registration
• no security
• not really faster than PPP

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Problem

• You are responsible for setting up some remote
  workstations and a server that will be connected
  to the Internet. The workstations will be
  connecting to the server using standard telephone
  ines. You know that SLIP and PPP are useful
  protcols for your situation. Your boss comes in
  and says, I think SLIP is the protocol we should
  start using here. What do you think? What
  protocol would you recommend? List three
  advantages to the recommended protocol.

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Circuit Switching

• like voice call on PSTN
• dedicated channel-always up
• no channel access delay
• inefficient use of transmission media
• requires more bandwidth
• connection delays

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Message Switching

• no dedicated path
• messages contain source and destination info
• also referred to as store-and-forward networking
• ex e-mail

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Message Switching, cont.

• Pros
• efficient traffic management through
  prioritization
• reduction of network traffic congestion
• efficient use of data channels
• asychronous communication across time zones
• Cons
• delays caused by store-n-forward
• unsuitable for real-time applications

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Packet Switching

• Advantages of circuit and message switching
  without any of the disadvantages
• Independent routing of packets
• bandwidth/load balancing
• dynamic rerouting
• Packet size restricted for efficiency and speed

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Datagram Packet Switching

• post-office analogy

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Virtual Circuit Packet Switching

• Virtual circuit (logical connection)
• All packets between the same start and end point
  use same logical connection (route)
• Used primarily for real-time, connection-oriented
  services like video and audio

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Planning for Packet Switching

• Pros
• PS improves use of network bandwidth
• PS has shorter transmission delays than circuit
  switching because of small packet size
• RAM vs. Hard drivegtPS requires more RAM MS
  requires more hard drive space
• ProcessorgtPS requires more processing power than
  MS
• Lost Packetsgtsequencing

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Connections

• Dial-up
• Dedicated Analog

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Connections, Cont.

• Digital
• T-carrier
• Switched 56

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X.25 and Frame Relay
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ATM
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ISDN
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FDDI
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SONET