Network Design Criteria

Every Computer Network set up needs to meet certain demands or requirements for the organization its being set up. These requirements are collectively studied under Network Criteria. The major criteria that a Data Communication Network must meet are:

1. Performance: Performance is the defined as the rate of transferring error free data. It is measured by the Response Time. Response Time is the elapsed time between the end of an inquiry and the beginning of a response. For example the time elapsed between the request for a file transfer and start of the file transfer. Factors that affect Response Time are:
• Number of Users: More the users on a network - slower the network will run.
• Transmission Speed: Speed that data will be transmitted with.
• Media Type: Type of physical connection used to connect nodes together.
• Hardware Type: Slow computers such as Celerons and Pentiums or fast such as the newer and faster ones based on Nehalem Micro-Architecture such as the i3, i5 and i7.
• Software Program: How well is the Network Operating System (NOS) written.
2. 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.
3. 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.
4. 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.
5. 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.

Hence performance, consistency, reliability, recovery and security are the very essential pre-requisites in a computer network. The better these parameters exist into the framework of a computer network, the better a computer network it is.

Following this, I'd advise you to read over an Introduction to Computer Networking and a general discussion over Relevance of Computer Networks. You're welcome to follow those links to expand your knowledge. Take care :)