Before we get into the details of the TCP/IP model, let's briefly go back in time. TCP was the first on the scene in 1973. In 1978, it got broken up into to two parts, TCP and IP, which replaced the Network Control Protocol (NCP) and was considered the official means to transport any data that would connect to ARPANET. Since 1983, ARPANET has been referred to as the internet.
TCP/IP became the foundation for the exponential growth and success of today's World Wide Web and the internal or private networks used by small to large businesses.
The TCP/IP model, or DoD model, is just a shortened version of the OSI model. Instead of having seven layers, it has four layers—or, at least, it did. For the new CCNA 200-125 certification, there is a new five-layer TCP/IP model.
Let's compare them:
Looking at the preceding...