A network is a system, or collection of systems, that facilitates the exchange of resources from one point to another. This is a fancy way of saying that a network is the sum of the parts connecting two or more points. Examples of networks include the subway, the highway system, the telephone system, and the Internet.
A network is made up of physical and logical components. The physical components are the cables and network hardware devices, such as switches. The logical components of a network are the frames and data carried by and across the network.
Networks have two points?the source and destination, also known as the origination and termination points (respectively).
There are three modes of transmission between origination and termination points: simplex (one-way) mode, half-duplex mode (two-way, but not at the same time), and full-duplex mode (two-way, at same time).
There are three major types of networks. The distinguishing characteristic of each network types is the geographic range covered by the network:
LANs cover a small geographic range?the area within an office building, for instance.
MANs cover a broader geographic range than LANs?the area of a city, for instance.
WANs cover a broad geographic range?an expanse across several states or countries, for instance.
The design, engineering, and implementation of a network are based on the application of network models and standards. A network model is a guiding principle in network communications, whereas a network standard is a network communications law. A vendor's special use of a standard is called a proprietary feature or proprietary implementation. Another example of proprietary feature is a product a vendor implements that is not based on a standard at all.