On the basis of their size, physical division, and their geographical division, computer networks can be categorized into three types. They are:

The computer network which is limited to a small area such as a room a building or a school and connects a limited number of computers is called Local Area Network (LAN). We can use a large number of computers in a LAN but it is restricted to a small geographical area. Local Area Networks are limited by distance. In order to keep the signal at a quality transmission level, it must be boosted by repeaters along the way. By creating a LAN, we can share resources such as hardware and software to transfer information between the computers. In a LAN, computers and other hardware such as printers can be connected by cable (copper wiring), fiber optic cabling (glass fibers).

The medium-sized network that covers the area larger than a LAN but smaller than a WAN is called Metropolitan Area Network (MAN). It covers a larger geographical area such as a university, an entire city, a valley, a district, or a zone. This type of network is prepared by connecting several LANs in different locations. To form a MAN, several LANs are connected through a telephone line, optical fiber cable,s or wireless communication media. A MAN is typically owned and operated by a single entity such as a government body or a large corporation. It is specially adapted by medium-sized organizations having different branches within a city or region.

The communication network, that spans globally and connects a large number of computers around the world is called Wide Area Network. It is the largest network in the world. It is not restricted to a geographical location. The Internet is an example of a WAN. To form a WAN, several LANs and MANs are connected through satellite links or microwave systems. These networks have become quite necessary in the current era, where day to day activities of many business organizations are spread. WANs are used by many companies for transmitting and receiving information among workers, customers clients, etc. across cities, regions, and countries. This technology is of high speed and very expensive to set up.

Network architecture describes how the computers on the network interact and communicate with each other. It is the combined form of network topologies and mode of data transmission between the computers in the network.

Generally, network architecture can be classified into two types:

The network mode in which there is at least one server and other clients is called a client-server model. This is a more common type of network architecture that uses a central server and specified network software. The server is dedicated and is only used to store files and run server tasks. The computers that connect to the server are called clients. In this network, each client can share the processing and storage with the server. The server provides the services to the clients whereas clients request the server for services. The server provides the services to the clients whereas clients request the server for services. The server should be a powerful computer with greater processing speed and large storage capacity than the client. Depending on the type of work the server may be of various types such as File server, Printer server, Message server, Application server, Web server, etc. In short, the client-server networks provided easier network administration with secure and manageable access to company data.

Some advantages of client-server network are as follows:

The Peer-To-Peer is a type of network architecture consisting of several computers which are connected to each other. In this type of network, all the computers function both as a client and a server, in which, each computer has equal responsibilities of providing and using resources. It has no central data storage.

The Peer-To-Peer network consists of shared folders located on computers within the network. These folders are set to shared status so that other people connected to the network can access them. Each shared folder is accessed by the users of the network, who set up a certain drive letter (say H:) as a p[ointer to be shared folders on the other computers. In addition, any printers connected to any computer can be shared with other network users.

Some advantages of peer-to-peer networks are as follows:

Central network architecture is a type of network where all users connect to a central server, which is the acting agent for all communications. This server would store both the communications and the user account information. Most public instant messaging platforms use a centralized network. So it is called centralized server structure.