As we all know that there are five layers of internet model. These are physical layer, data link layer, network layer, transport layer and application layer. The physical layer controls and coordinates the functions required to transmit a bit stream over a physical medium. It deals with the mechanical and electrical specifications of the interface and transmission media. It also defines he procedures and functions that physical devices and interfaces have to perform for transmission to occur. The data link layer transforms the physical layer, a raw transmission facility, to reliable link. It makes the physical layer appear error free to the upper layer i.e. Network layer. Network layer is responsible only for the source to destination delivery of a packet possibly across multiple networks. While the data link layer oversees the delivery of the packet between two systems on the same network. The network layer ensures that the each packet gets from its point of origin to its final destination. The transport layer is responsible for process to process delivery of the entire message whereas the network layer oversees host to destination delivery of individual packets. The transport layer ensures that whole message arrives intact and in order, overseeing both error control and flow control at the process to process level. Application layer enables the user, whether the human or software, to access the network. It provides user interfaces and support for services such as electronic mail, remote file access and transfer, access to the World Wide Web and so on.
