what are the three criteria necessary for an effective and efficient network?

Network Criteria: 

To be considered effective and efficient, a network must meet a number of criteria. The most important of these are performance, reliability, and security.

Performance:
Performance can be measured in many ways, including transit time and response time. Transit time is the amount of time required for a message to travel from one device to another. Response time is the elapsed time between an enquiry and a response.

The performance of a network depends on a number of factors, including the number of users, the type of transmission medium, the capabilities of the connected hardware, and the efficiency of the software.

Number of users:

Having a large number of concurrent users can slow response time in a network not designed to coordinate heavy traffic loads. The design of a given network is based on an assessment of the average number of users that will be communicating at any one time. In peak load periods, however, the actual number of users can exceed the average and thereby decrease performance. How a network responds to loading is measure of its performance.

Type of transmission medium:

The medium defines the speed at which data can travel through a connection. Today’s networks are moving to faster and faster transmission media, such as fiber-optic cabling, a medium that can carry data at only 10 megabits per second. However, the speed of light imposes an upper bound on the data rate.

Hardware:

The types of hardware included in a network affect both the speed and capacity of transmission. A higher-speed computer with greater storage capacity provides better performance.

Software:

The software used to process data at the sender, receiver, and intermediate nodes also affects network performance. Moving a message from node to node through a network requires processing to transform the raw data into transmittable signals, to route these signals to the proper destination, to ensure error-free delivery, and to recast the signals into a form the receiver can use. The software that provides these services affects both the speed and the reliability of a network link. Well-designed software can speed the process and make transmission more effective and efficient.

Reliability:

In addition to accuracy of delivery, network reliability is measured frequency of failure, the time it takes a link to recover from a failure, and the network’s robustness in a catastrophe.

Frequency of failure:

All networks fail occasionally. A network that fails often, however, is of little value to a user.

Recovery time of a network after a failure:

How long does it take to restore service? A network that recovers quickly is more useful than one that does not.

Catastrophe:

Networks must be protected from catastrophic events such as fire, earthquake, or theft. One protection against unforeseen damage is a reliable system to back up network software.

Security:

Network security issues include protecting data from unauthorized access and viruses.

Unauthorized access:

For a network to be useful, sensitive data must be protected from unauthorized access. Protection can be accomplished at a number of levels. At the lowest level are user identification codes and passwords. At a higher level are encryption techniques. In these mechanisms, data are systematically altered in such a way that if an unauthorized user intercepts them, they will be unintelligible.

Viruses:

Because a network is accessible from many points, it can be susceptible to computer viruses. A virus is an illicitly introduced code that damages the system. A good network is protected from viruses by hardware and software designed specifically for that purpose.