Computing fundamentals units 5 and 6

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5. Data transmission

a.  describe the charasteristics of a LAN and a WAN

LAN

  • over a small area
  • more secure 
  • doesnt require communication devices
  • hard wired or wireless for of central point

WAN

  • geographically remote
  • tends to use external communications
  • subject to attack/interceptions
  • requires a modem

b. show an understanding of the hardware and software needed for a LAN and for a WAN

LAN 

  • router
  • switch
  • hubs
  • NIC card
  • Network Operating System (NOS)

WAN

  • routers
  • modems
  • telephone cabling or fibre optic cable

c. describe the different types of data transmission

serial: one bit transmitted at a time through a single wire

parallel: multiple bits transmitted at a time through many wires (e.g. video streaming) 

half duplex: communication in both directions but one at a time

duplex: communications in both directions simultaneously 

d. explain the realtionship between bit rate and thetime sensitivity of the information

bit rate: the rate at which data is transferred measured in bits per second. Actual rate of transmission can vary because of other factors like the need to transmit control signal.

e. recognise that errors can occur in data transmission, and explain methods of detecting and        correcting these errors 

parity checking: when one bit in every byte is added to the word thus ensuring the total number in the byte is even (even parity) or odd (odd parity). If the data that has been send doesnt correspond to the parity chosen then the receiver askes the sender to re-send it.

echoing: the reciever echoes back to the sender everything that is sent. If the sender doesnt get back what it sent, it re-sends the byte.

checksum: it is a calculation carried out  on a packet of data. The result is added to the packet and sent. the recipent  carries out the same calculation and if the answer is the same as

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