The OSI model
defines internetworking in terms of a vertical stack of seven layers. The upper layers
of the OSI model represent software that implements network services like encryption and connection management. The lower layers
of the OSI model implement more primitive, hardware-oriented functions like routing, addressing, and flow control.
In the OSI model, data communication starts with the top layer at the sending side, travels down the OSI model stack to the bottom layer, then traveses the network connection to the bottom layer on the receiving side, and up its OSI model stack.
The OSI model was introduced in 1984. Although it was designed to be an abstract model, the OSI model remains a practical framework for today's key network technologies like Ethernet and protocols like IP.
Also Known As: Open Systems Interconnection (OSI) reference model, OSI seven layer model
Internet Protocol (IP) corresponds to the Network layer of the OSI model, layer three. TCP and UDP correspond to OSI model layer four, the Transport layer. Lower layers of the OSI model are represented by technologies like Ethernet. Higher layers of the OSI model are represented by application protocols like TCP and UDP.