Computer networking refers to the study and analysis of the communication process among various computing devices or computer systems that are linked or networked, together to exchange information and share resources. Computer networking depends on the theoretical application and practical implementation of fields like computer engineering, computer sciences, information technology and telecommunication. Today the world scenario is changing. Data Communication and network have changed the way business and other daily affair works. Now, they rely on computer networks and internetwork. A set of devices often mentioned as nodes connected by media link is called a Network. A node can be a device which is capable of sending or receiving data generated by other nodes on the network like a computer, printer etc. These links connecting the devices are called Communication channels. Computer network is a telecommunication channel through which we can share our data. It is also called data network. The best example of a computer network is the Internet. Computer network does not mean a system with control unit and other systems as its slave. It is called a distributed system. Computer networks can be broken down historically into topologies, which is a technique of connecting computers. The most common topology today is a collapsed ring. This is due to the success of a network protocol called the Ethernet. This protocol, or a network language, supports the Internet, Local Area Networks, and Wide Area Networks. A router, network card and protocols are the essential pillars upon which any network is built. Computer networks are the backbone of modern-day communication. Even public switched telephone networks are controlled by computer systems; most telephonic services are also working with IP. The increasing scope of communication has led to much advancement in the networking field and in its relative industries like hardware, software manufacturing and integration.