Networks and Telecommunications

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Networks and Telecommunications
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Telecommunications Media

• Twisted pair (RJ-11 RJ-45)
• Advantages
• Disadvantages
• Coax
• Fiber-optic

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Communication channels their capacities
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Capacities of other communication media
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Telephone company connection choices
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Telecommunications Media-wireless

• Microwave
• Satellite
• Cellular
• Infrared laser

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Transmission Modes

• Simplex
• Half-duplex
• Full-duplex
• Echoplex (re-x-mit for check)

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The signal

• Analog
• Digital
• Modems
• Serial vs. parallel
• Asynchronous vs. synchronous (character vs. block
  per unit time!)

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Networks

• A computer network is a collection of computers
• and other devices that communicate to share data,
  
• hardware and software.
• LANs
• topologies
• protocols (polling vs. contention vs. token)
• WANs
• PBXs
• gateways vs. bridges (dissimilar vs. similar)

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What sort of resources does a LAN provide?
Network nodes include workstations printers,
and servers.
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LANs

• When you start a program that is stored on a LAN,
  the program is copied to your workstations RAM,
  then runs normally.
• With proper licensing, many users on the same
  network can use the same program simultaneously,
  also known as sharing.
• Sharing is effective because
• less disk storage space required
• easier to update software
• less expensive

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LAN topologies

• Ring
• Bus
• Star
• Hierarchical
• Hybrid
• ExampleMSCDs network

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LAN Hardware

• Hubs
• To connect workstations
• together and then
• to the server
• Server types
• dedicated servers
• non-dedicated servers
• print servers
• application servers
• host computers

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Dedicated file server

• Which of the servers processes my data?
• Dedicated server delivers programs and data files
  to workstations.
• It does not process data or run programs for
  workstations.

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Dedicated file server
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Non-dedicated file server

• Which of the servers processes my data?
• A non-dedicated file server is a computer on a
  network that performs a dual role as both file
  server and workstation processes the data
• also called peer-to-peer capability
• Print server - receives files from workstations
  and forwards them to a specific network printer
• A print server manages a print queue, a holding
  area for files waiting to be printed.

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Non-dedicated file server
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Application server

• A computer that runs a specific application
  software package also processes data
• also referred to as client/server architecture
• An application server splits processing between
  the workstation (client) and the network
  (server).

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Application server
An application server typically runs database
software and performs database functions as
requested by the workstations.
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Components of a LAN

• LAN The components are usually located within a
  half mile of each other.
• SWITCH located in the center, is a
  special-purpose computer that receives and
  transmits messages to computers in the LAN.
• NIC A network interface card
• is a hardware component that
• connects each devices circuitry
• to a cable allowing protocols to
• send data across the LAN.
• Most new computers have an
• onboard NIC built into the
• computers circuitry.

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Host computers

• A minicomputer or a mainframe with attached
  terminals.
• all processing takes place on the host
• terminals only display results of processing
• also known as a time-sharing system
• MSCDs Clem is a host computer (see Pine, Clems
  own mail system, or Pico, Clems own editor)
• Terminal emulation software connects a
  microcomputer to a host (see Telnet)

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What protects your computer while on the network?
Also firewalls in computers!
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End Networks and Telecommunications