3) Data Transmission

• What is serial transmission?

  Serial transmission can only send one bit at a time in order.
• What is parallel transmission?

  Parallel transmission can send more than one bit at a time.
• Advantages of serial transmission?

  It is cheap as it uses one wire, it is reliable over long distances
• Disadvantages of serial transmission?

  it is slower than parallel transmission in the short term.
• Advantages of parallel transmission?

  It transmits faster than serial transmission, reliable for shorter distances
• Disadvantages of parallel transmission?

  data needs to arrive at the same time and sync up.
• What is a simplex?

  A simplex is uni-directional and allows data to be sent but the receiver cannot send data back. For example a satellite connection to a TV.
• What is a half duplex?

  A half duplex is bi-directional and allows data to be sent in both directions but not simultaneously. For example a walkie talkie.
• What is a full duplex?


  A full duplex allows data to be sent simultaneously in both directions. For example a phone call.
• What is multiplexing?

  It is the method of combining several independent data sources for sending along a single route to get to a single destination on the same wire.
• What is circuit switching?

  The path is set up between the sender and receiver, All data follows the same path in order, Path cannot be used by any other data
• What is packet switching?


  Data is split into packets, Each packet may be transmitted by different routes, Packets may arrive out of order and are re-assembled
• Why is packet switching more preferred?

  Better security as it is very difficult to intercept, Makes more efficient use of data lines as there is no waiting during gaps, Less likely to be affected by network failure
• What is in the header part of the packet?

  source address, destination address, order number
• What is in the payload part of the packet?

  data
• What is in the trailer part of the packet?

  error check, end of packet bits
• What is network collision?

  Data collision occurs when two sets of data are detected on the network simultaneously, Once detected the transmitting nodes re-sends after a short random amount of time.
• What is routing?

  This is the method of selecting the path across a network for data packets to be sent.