OSI%20Model

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OSI Model

• CS363-Winter 1999
• DePaul University

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Group Project Info

• Teams formed and on the web
• Cases
• Working in Groups
• Last half of class tonight reserved for projects

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Review 1

• You must connect a research institutions main
  offices with the testing site 30 miles away. You
  will connect them with fiber optic cable. Which
  type of fiber will you use and why?

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Review 2

• You are replacing your thicknet backbone between
  your servers with a high-speed network cable. You
  are considering using Category 5 twisted-pair
  copper or multimode fiber cable.
• Under what circumstances will you install the
  fiber?
• Under what circumstances will you not use fiber?

5
Review 3

• Your company recently renovated its telephone
  system, including cabling, and had extra cable
  installed for future growth. Now you would like
  to use the excess cabling to network the
  computers in your company.
• What sort of network performance (data capacity
  and cable length) can you reasonable expect from
  these new telephone cables?
• What could you do with the old telephone cable
  that is still in the building?

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Review 4

• You would like to attach your notebook computer
  to your LAN, but it does not have a PCMCIA slot
  or a place for a proprietary network card. How
  can you attach it to the network?

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OSI Model

• Why do we keep talking about this? Why should we
  care?

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Protocol Stacks

• gtgroup of protocols arranged on top of each
  other as part of a communications process.
• Importance of protocol stacks

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Peer-Layer Communication Between Stacks
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Physical Layer

• Functions
• Components

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Data-Link Layer

• Functions
• Components

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Network Layer

• Functions
• Components routers and gateways

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Transport Layer

• Functions
• Components

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Session Layer

• Functions
• Components

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Presentation Layer

• Functions
• Components

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Application Layer

• Functions
• Components

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Problem

• Your company wants to use data link layer
  encryption devices to send private data over a
  public wide area network. What effect will this
  have on devices in other layers?

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Problem

• When trouble-shooting your network with a packet
  sniffer, you find a device generating spurious
  TCP/IP packets. Which devices are suspect?

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Drivers

• gt
• NDIS
• ODI

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Network Protocols

• gtagreed-upon ways in which computers exchange
  information

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How Protocols Work

• Sending
• Packetize data
• Appropriately address the packets
• Present packets to the network for delivery
• Receiving
• -Accept packets from the network
• Remove transmitting information (addresses) added
  in the sending process
• Reassemble data packets into original message

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Network Packets

• Packet Structure
• Headergt
• Datagt
• Trailergt

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Packet Assembly

• Routing
• Protocol Stacks

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Binding Protocols
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Two Types of Protocols

• Connection-Oriented

• Connectionless

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Standard Protocol Stacks

• ISO/OSI
• SNA
• DECnet
• NetWare
• AppleTalk
• TCP/IP

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Microsoft Supported Transport Protocols

• NetBEUI
• NWLink
• TCP/IP

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Other Protocols whose names you should know

• SMTP
• SNMP
• NFS
• X.25
• X Windows

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Problem

• Your boss wants you to speed up the office LAN
  without spending any money. You are currently
  using 10Mbps Ethernet and TCP/IP. Users connect
  to the Internet using dial-up modems, and a
  single Ethernet domain is in use. What do you
  do?

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Problem

• Your company network has become very slow, so you
  decide to break it up into multiple domains and
  use a router to connect the domains. As soon as
  you disconnect the networks, even with the router
  running properly, you cant get data between
  networks. You are using four Windows NT servers
  (one in each subnetwork) running on Ethernet with
  NetBEUI. Youve spent your budget on the router
  and cant afford to purchase new hardware. What
  is wrong? How can you fix it?