Introduction to Data Communications
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6. Criteria for a Data Communication Network

The major criteria that a Data Communication Network must meet are:

Performance
Consistency
Reliability
Recovery
Security

6a. 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:

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

6b. Consistency

Consistency is the predictability of response time and accuracy of data.

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!
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.

6c. 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.

6d. Recovery

Recovery is the Network's ability to return to a prescribed level of operation after a network failure. This level is where the amount of lost data is nonexistent or at a minimum. Recovery is based on having Back-up Files.

6e. Security

Security is the protection of Hardware, Software and Data from unauthorized access. Restricted physical access to computers, password protection, limiting user privileges and data encryption are common security methods. Anti-Virus monitoring programs to defend against computer viruses are a security measure.