COMPUTER DATA COMMUNICATION

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COMPUTER DATA COMMUNICATION NETWORKS

• COMMUNICATION DEVICES

Presented by MUTAASA AHMED
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WHAT ARE COMMUNICATION DEVICES?

• Communication devices are peripheral devices
  used for communication between computers and
  other devices. Machines that assist in
  transmission of data

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THE COMMUNICATION PROCESS / MODEL
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COMMON COMMUNICATION TASKS

• Data encoding the process of transforming input
  data or signals into signals that can be
  transmitted
• Signal generation generating appropriate
  electro-magnetic signals to be transmitted over a
  transmission medium
• Synchronization timing of signals between the
  transmitter and receiver when a signal begins
  and when it ends duration of each signal

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• Error detection and correction ensuring that
  transmission errors are detected and corrected
• Flow control ensuring that the source does not
  overwhelm the destination by sending data faster
  than the receiver can handle
• Addressing indicating the identity of the
  intended destination
• Routing selecting appropriate paths for data
  being transmitted

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• Message formatting conforming to the appropriate
  format of the message to be exchanged
• Security ensuring secure message transmission

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NIC ADAPTERS

• Also called (the Network Adapter, the Ethernet
  Card or the local area network card)
• A computer circuit board/card that is installed
  in a computer to facilitate communication to a
  network, such as a home network or internet using
  an Ethernet cable with an RJ-45 connector.

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• Wireless cards can also be used especially in
  Laptops that dont have a built in Wireless
  Network option.

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ROUTERS

• Routers are intelligent devices that route data
  to destination computers or networks.
• Routers are designed to transmit data from
  network users to specific locations along the
  path which means that
• Routers facilitate the sharing of a network
  connection with multiple machines increasing
  productivity.

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FUNCTIONS OF A ROUTER ON A COMMUNICATION NETWORK

• Restrict network broadcasts to the LAN. Routers
  control network broadcasts limiting the
  possibility of collisions.

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• To act as a default Gateway Computers on one
  network have the ability to communicate with
  other computers on geographically different
  locations (for example when using the internet).
  The local router acts as a default gateway that
  receives the data (from the local network), looks
  and forwards the data to the remote address of
  that far-away computer.

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• Move data between networks
• Its worthy noting that the more connections made
  on a router, the network significantly slows
  down.

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HUBS

• Join multiple computers (or other network
  devices) together to form a single network
  segment.
• Hubs contain multiple ports (RJ-45 ports) that
  each accept a network cable. Small networks may
  require small hubs of about 4 or 5 ports

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• the 5th being for UPLINK. Bigger hubs can
  contain 8, 12, 16 or 24 ports depending on
  necessity. When a packet (data) arrives at one
  port, its copied to the other ports. Below is an
  example of a hub

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Its possible to connect multiple hubs together
in order to centralize a large number of
machines. The resultant connections are called a
Daisy Chain.
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• One hub is connected to another using a
  cross-over cable to the UPLINK port. You can
  connect up to 3 hubs together.

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SWITCHES

• They are almost similar to hubs however, they
  are more intelligent.
• Switches analyze the data packets coming in from
  its entry ports, filters the data and forwards it
  to the targeted recipient port (its called
  switching).

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• Switching tables store the MAC (Media Access
  Control Address) of each device that is connected
  to the network and sends the data to only the
  intended address.

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HOW INTELLIGENT ARE SWITCHES??

• If you have 4 computers connected to hub (ABCD),
  computer A wishes to talk to computer B, the
  traffic will be passed to all four computers
  (usually called broadcast), but only computer B
  will accept it. This broadcasting feature will
  generate lot of traffic and slow down your
  network.

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• However it will be the other story if you use a
  network switch it will be smart enough to
  determine that only computer B is needed to talk
  with in this situation, then the traffic is only
  sent to computer B. Overall network switches
  improve your network performance.

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GATEWAYS

• Its a hardware/software for connecting two
  networks together in order to serve as an
  interface between different network protocols.

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• When a remote user contacts the gateway, it
  examines the request based on the rules set by
  the network administrator and if the request
  passes the test, the gateway creates a link
  between the two networks.

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BECAUSE OF GATEWAYS,

• There is continuity between networks (building
  bigger and bigger networks)
• Better security as incoming and outgoing
  information is carefully scrutinized for any
  malicious content or activity before
  transmission.

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MODEMS

• From the words Modulation and Demodulation
• These are devices for transmitting digital data
  over telephone lines by modulating the data into
  an audio signal to send it and demodulating the
  signal to receive it.
• Analog to digital for your computer to read

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• Digital to analog to be sent to your ISP
• The most common modem is the one connected to
  each computer which we use to connect to the
  internet using our telephone line and dialing
  your ISP

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REPEATERS

• On a transmission line or medium, the signal
  suffers from distortions and therefore becomes
  weaker as the distance between the two active
  agents widens
• The repeater is used for refreshing a signal
  thereby extending the range of the network (a
  repeater repeats the signal)

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CABLES

• These are used to connect communication devices
  with each other to form a network. Devices
  include individual work stations, printers,
  scanners, camera etc.

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• -END-