A network is a collection of entities that exchange information or goods. Few examples of networks are the nervous system, the traffic light system, the 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 computers consist 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 must know the history of computer network. The first communicating computer networks included the military radar system. The Semi-Automatic Ground Environment (SAGF) ​​was started in the late 1950s. By the early 1960s, individual computers had to be physically shared, making it difficult to share data and other information. Seeing that this was impractical, researchers developed a way to connect computers so they could share their resources more efficiently. Thus the first computer network was born. Through the then new communication protocol known as packet switching, numerous applications became possible, such as secure voice transmission in military channels. These new circuits provided the basis for the communications technologies of the rest of the 20th century, and with further refinements, these were applied to computer networks. These networks provided the basis for the first ARPANET, the precursor to the modern Internet. The Advanced Research Projects Agency (ARPA) submitted the proposal for the project on June 3, 1968, which was approved a few weeks later. With this proposal entitled "Resource Sharing Computer...... middle of paper......", ARPANET (Advanced Research Project Agency Network) began in the late 1960s. Its main goal was to provide network connections 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) monitors the standards and future of the Internet. Today, computer networks are the core of modern communication. All modern aspects of the public switched telephone network are computer controlled. And telephony increasingly works via the Internet Protocol, although not necessarily over the public Internet. The scope of communication has increased significantly in the last ten years and this communication born in communication would not have been possible without the progressively advancing computer network.