Introduction to Data Communications
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11. Data Communication Network

The major criteria that a Data Communication Network must meet are:
  1. 11a. Performance
  2. 11b. Consistency
  3. 11c. Reliability,
  4. 11d. Recovery and
  5. 11e. Security

11a. Performance

Performance is the defined as the rate of transferring error free data. It is measured by the Response Time. Response Time is the elasped time between the end of an inquiry and the beginning of a response. Request a file transfer and start the file transfer. Factors that affect Response Time are:

  1. Number of Users: More users on a network - slower the network will run
  2. Transmission Speed: speed that data will be transmitted measured in bits per second (bps)
  3. Media Type: Type of physical connection used to connect nodes together
  4. Hardware Type: Slow computers such as XT or fast such as Pentiums
  5. Software Program: How well is the network operating system (NOS) written

11b. Consistency

Consistency is the predictability of response time and accuracy of data.
  1. Users prefer to have consistent response times, they develop a feel for normal operating conditions. For example: if the "normal" response time is 3 sec. for printing to a Network Printer and a response time of over 30 sec happens, we know that there is a problem in the system!
  2. Accuracy of Data determines if the network is reliable! If a system loses data, then the users will not have confidence in the information and will often not use the system.

11c. Reliability

Reliability is the measure of how often a network is useable. MTBF (Mean Time Between Failures) is a measure of the average time a component is expected to operate between failures. Normally provided by the manufacturer. A network failure can be: hardware, data carrying medium and Network Operating System.

Introduction to Data Communications
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