TCP/IP is a suite of communication protocols developed in the 1970s by the Defense Advanced Research Projects Agency (DARPA) of the U.S. Department of Defense. It was developed on DARPA's network called ARPANET and further evolved to be used for communication on the Internet. Today, all computers connecting to the Internet or Internet-like private wide-area networks are essentially using this protocol.
Although computers are capable of exchanging data with each other using several data transfer methods, communication by its very definition requires the transferred information to be understood on the receiving end. A communication protocol is like a language; it enables computers to communicate with each other so that the receiving computer understands the data sent to it. TCP/IP standardizes this communication process by offering one universal protocol for all the computers over the Internet to use in their communication with each other.
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Just as in human communication, computers may use several different languages to communicate with each other. Some protocols may be more suitable for use in certain private networks than TCP/IP. However, TCP/IP even enables such networks to be connected to the Internet. Furthermore, it lets computers and devices with different hardware architectures and running different operating systems communicate with each other. This means a computer running Windows can connect to a web server running Linux to browse the website hosted there. It is quite similar to the use of English as an international language today.
TCP/IP assigns each computer on the network a unique address called its IP address. Thus, every computer on the network is uniquely identifiable and information could be sent to it by simply addressing its IP address. The present implementation of IP addressing is known as IPv4, while a newer implementation supporting a much larger number of unique addresses called IPv6 is being developed to replace IPv4.
Communication with TCP/IP starts with a connection being established between the two computers. This is achieved in a systematic manner, called the three-way TCP handshake. The computer initiating the communication sends a connection request packet to the other computer. If the computer is the one with the correct IP address, it sends a packet back. If the first computer receives that packet, it sends another one to the second computer, the reception of which by the latter establishes a connection. The information is then exchanged using this established connection, reducing the risk of the data being compromised.