In computer networks, computers exchange information, with the help of a communication channel. These communication links/channels result in a network. These systems can share files and other resources amongst themselves.
Network is defines as an interconnection of computers.
The computers in a network may be linked through cables, telephone lines, radio waves or satellites.
In a network individual computer which accesses shared network recourses, are known as workstation or node or terminal.
And the computer that provides resources to other computers on the network is known as the server.
Telecommunication channels
The media that join the components of a network are called telecommunication channels. Few examples of telecommunication channels are copper wires, co-axial cables, Optical fiber cables, etc.
The need of Computer networks
The network is needed for communication, information sharing, resource sharing, and high reliability.
Types of computer networks
There are some basic classifications of networks
1) Local area network (LAN)
This network is generally operated within an organization. Connections are usually made through electric cables that link all the machines.
Advantage
- The addition or deletion of a workstation to the network is easy.
- A high rate of data transmission is possible.
- Peripheral devices like printer can be shared by other computers.
Disadvantage
- There are some errors in data transmission.
- If the communication line fails, the entire network system breaks down.
2) Wide area network (WAN)
This network connects the computer systems across long distances.
For example, different cities, countries, or continents.
A WAN may comprise of many LANs.
Computers in a WAN are connected through telephone services via electronic units called MODEMs, or through Integrated Services Digital Network (ISDN), a dedicated high-speed line that carries digital signals.
The Internet is an example of WAN.
Advantage
- WANs are used to connect (LANs) and other types of networks together, so that the users and computers in one location can communicate with the users and computers in other locations.
Disadvantage
- It is slow and costly as compared to LAN.
- There are more errors in data transmission as compared to LAN.
3) Metropolitan area network (MAN)
MAN is a hybrid of LAN and WAN. This type of network is inherent in a single town or city.
Advantage
- It is less expensive and easily accessible,
- It can be used by big organizations.
Disadvantages
- It is limited to small geographical areas such as city level.
Computer networks topologies
The physical layout or the design of a computer network is called the topology. It defines the arrangement in which the workstations in a network are interconnected. Common topologies include Star, Bus, Ring, Tree, and Graph.
1) Bus network
In this network, a single cable (bus) is shared by all the devices.
Each node is connected to the bus by an interface called a tap.
If one node in the network fails, the working of the rest of the network is not affected.
An example of bus topology is Ethernet.
The main advantage of the bus network is that it has low cabling cost and the insertion of a new node in the network does not disturb the rest of the nodes.
2) Tree network
Another variation of the bus topology is the tree topology.
In this network, each node is treated as a host computer of another star topology. Therefore, a tree-like structure is formed.
This topology is best suited for applications that have a hierarchical flow of data and control.
3) Ring network
This network links devices by a cable in a loop as a circle.
There is no central node in this configuration.
Data is transmitted around the network, with the nodes picking those messages which are addressed to them.
Data flows in one direction only.
The breakdown of one node disables the whole network. Therefore, it is less recommended.
4) Star network
This network is designed in the pattern of a star.
Each node in the network is connected to a central computer known as a server that controls the whole network.
Each node is independent of the others, which means that if a fault occurs in it, then the rest of the network will not be affected.
But if the central node goes down, so does the whole network.
This type of topology is mainly used in WANs.
5) Graph network
In this network, nodes are connected to each other in a random manner. A node may be connected to any number of nodes through links.
Computer Networks protocols
A protocol in networking defines the rules and procedures that must be followed by all the nodes while transmitting data.
These rules are broken into small software programs that handle communication links. Some popular protocols are TCP/IP, HTTP, FTP, SMTP, etc.
Computer Networks Architecture
Network architecture means the design and implementation of a network with respect to its protocols and topology.
It also deals with the transmission of data, error handling, security, etc. common network architectures are OSI (open system interconnection) and SNA (system network architecture).
Network architectures can be broadly classified into Peer-to-Peer architecture and Client/Server architecture
1) Peer-To-Peer architecture
This network has no servers, which means that all workstations have equal capabilities. Peer-to-peer networks are for resource sharing, files, and data sharing and email. These networks support only a few machines.
2) Client/server architecture
This network consists of servers and work stations (also known as clients).
There may be several types of servers in this configuration file server, pointer servers, and network servers.
When a request is made by the client at the front end, it is passed to the server at the back end, which searches for the appropriate resource and sends back the information required.
The client/server network can cover a large geographical area.
Advanced Topic
Intranet
An intranet is an information portal designed specifically for the internal communications of small, medium, or large businesses, enterprises, governments, industries, or the financial institutions of any size or complexity.
Intranets can be custom- designed to fit the exact needs of businesses no matter where they are situated.
Extranet
An extranet is somewhat similar to an intranet.
Extranets are designed specifically to give external, limited access to certain files of your computer system to certain large or privileged customers, selected industry partners across the world, etc.
Internet
The Internet is also known as the NET.
It is the network of networks.
The Internet consists of thousands of smaller networks that communicate with one another.
Basic applications of internet
Searching
A huge amount of information is available on the internet on various subjects.
The Internet is like an online library.
Search engine is the special website that enables us to search the web systematically.
E-mail stand for electronic mail. It is one of the easiest methods of communication.
E-mail service is cheaper and faster compared to postal services.
Browsing
The process of clicking from one hyperlink to another on the World Wide Web (WWW) is called browsing. We can search for a particular piece of information.
Online chat/video calling
Chat is one of the fastest ways of communicating with other people over the internet. It refers to people holding live keyboard conversation.
And nowadays the is a facility of video calling threw different type of application in the market like Skype, etc.