Networks: LANs, WANs and Communication Protocols

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Networks LANs, WANs and Communication Protocols

• How do computers communicate?

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Resource sharing

• Printers
• Files
• Email

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Communication Protocols

• Non-routed (similar to a home phonethat everyone
  in the house shares good for a few people)
• Example Netbui
• Routed (similar to an operator-directed phone
  system-good for a large company)
• Example TCP/IP

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Routers

• A routed protocol such as TCP/IP uses routers
  (similar to the operators in the phone system) to
  direct information.

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Local Area Network (LAN)

• Uses one protocol and is usually in a small
  (local) area.
• Diagram

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Wide Area network (WAN)and Gateways

• A WAN is a group of LANs loosely connected via
  gateways.
• A Gateway helps to translate and allow
  communication across LANs that have different
  protocols.
• Diagram

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ARPA-NET

• Funded by the Dept. of Defense
• Goal was to develop a robust distributed network
  with no central place.
• Concerned about a nuclear attack from the Soviet
  Union
• Slowly developed into the Internet

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Client/Server Model

• Client The Software program that requests the
  use of a shared resource
• Server The software program that allows the use
  and sends the requested resource

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IP Address

• The machine name required by TCP/IP protocol
  for every computer on the network.
• Four groups of number separated by a period.
• Used by routers just as an address is used by the
  postal (snail) mail carrier.

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Domain Name

• An English-like machine name that is easier to
  remember than an IP address
• There are look-up tables to match IP addresses to
  Domain Names.

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Domain Name Server (DNS)

• A server program that provides the correct IP
  address for a Domain Name.
• The client browser may go through two steps
• Request the proper IP address from the Domain
  Name Server (DNS) located at your ISP.
• Request the web page from the web server located
  at the requested IP address.

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Uniform Resource Locator (URL)

• Specifies the exact location of a resource.
• Three parts protocol service, machine name and
  resource
• http//acc6.its.brooklyn.cuny.edu/cc312/lab1.htm
• ftp//www.sci.brooklyn.cuny.edu
• C\resources\printer1
• l