Conceptually speaking, the Internet can be viewed as consisting of four functional layers: the Link Layer, the Internet Layer, the Transport Layer, and the Application Layer. Each layer has several protocols, sets of rules that define how data is formatted and transmitted, which are known collectively as the Internet Protocol Suite. We’ll discuss all four layers here, but we’ll dive deepest into the Internet Layer and its associated Internet Protocol (IP)—because this is the worldwide network’s most fundamental component.
The Link Layer is the lowest layer and is responsible for delivering data over whatever hardware is in use. A link consists of the physical and logical components that are used to interconnect host computers and other types of network nodes (a node is any electronic device that’s connected to the network, including hosts). Link Layer protocols, including Address Resolution Protocol and Media Access Control, operate only on a host’s link.
Continue reading about Internet Protocol after the jump.