A network is a collection of entities that exchange information or goods. Few examples of networks are nervous system, traffic light system, railway system, etc. Computer network is normally known as a system of interconnected computers and communication devices that can communicate with each other and share resources. At the most basic level, the computer consists of two computers connected together by a cable to allow them to share data. A device connected to a network is called a node. A node can be a device such as a computer, printer, workstation, etc. When we talk about computer network, we need to know the history of computer network. The first communicating computer networks included the military radar system. The Semi-Automatic Ground Environment (SAGF) ​​began in the late 1950s. By the early 1960s, individual computers had to be physically shared, making it difficult to share data and other information. Realizing this was impractical, researchers developed a way to connect computers so they could share resources more efficiently. This is how the first computer network was born. Thanks to the new communications protocol known as packet switching, a number of applications, such as secure transmission of voice over military channels, have become possible. These new circuits formed the basis of communications technologies for the rest of the 20th century, and with further refinement they were applied to computer networks. These networks formed the basis of the first ARPANET, the precursor to the modern Internet. The Advanced Research Projects Agency (ARPA) submitted the project proposal on June 3, 1968 which was approved a few weeks later. This proposal titled "Resource Sharing Computer...... middle of paper......, the ARPANET (Advanced Research Project Agency Network) began in the late 1960s. Its main goal was to provide links networked between universities, research organizations and remote computer centers. No person, government, or entity owns or controls the Internet. Instead, an international non-governmental volunteer organization called the Internet Society (ISOC) controls the standards and future of the Internet. Today, computer networks are at the heart of modern communication. All modern aspects of the public switched telephone network are controlled by computer. And telephony increasingly works over Internet Protocol, but not necessarily over the public Internet. The scope of communication has increased significantly over the past decade, and this would not have been possible without the gradual evolution of computer networks..