Types of Networks

In this section, let us try to discuss the types of computer networks as they have evolved from a technical point of view. In this context, it may be stated that computer networks can be classified using different criteria, however, there is no single set of exclusive categories into which all types can be fitted. 

Generally, networks can be characterised as local area networks (LANs) metropolitan area networks (MANs) or wide area networks (WANs). As their/ names imply, the former are usually limited to a geographical area that extends no more' than a few miles between the extremities. Because of smaller distances involved, LANs, usually operata at a relatively high speeds of between 100 kilobits/sec to 100 M Bitsfsec. The Ethernet, the token Ring, and FDDI (fiber distributed data interface) are examples of com my used LANs operating at speed up to 10, 16, and 100 M bits/Sec. respectively. WAN .1' cover distances of hundreds or thousands of miles, and, in general, uses a variety a transmission media leased from common carriers. Some times networks are also characterised as: 

Private - such networks are usually owned by some corporation or other entity that confines access and use of network services to its staff. 

Public - this visually refers to entities that of networking or network services to any organisation or individual that whishes to subscribe. The telephone system is an example of a public network.

Cooperative -- this refers to networks that are supported and managed by their users. BITNET is an example of this type. 

Integrated Services Digital Network (ISDN) -- The development of public data networks for digital communications led to the existence of different networks for different purposes. This resulted in the duplication of networks. To avoid this, interconnection of two or more compatible or incompatible networks to form an intemet (network of networks) is attempted. The main aim of ISDN is to build a public network providing end-to-end digital connectivity which is capable of supporting a range of digital devices and services, both voice and non-voice, on the same basis. This allows users to send and receive data, text and image from computer systems as well as offering an enhanced telephone service. This is achieved over a single ISDN connection, so that one network can be used for all applications, providing higher speeds of transmission. 

Having known the different types of networks, let us now try to understand their objectives.