The Network Interface Layer
The functions of the data link layer and the physical layer of the OSI model have been combined into a single layer called the network interface layer in the TCP/IP reference model. This layer is responsible for dividing the data sent by the internet layer into logical groups called forms. Depending on the type of connection which could be connection oriented or connectionless this layer adds appropriate headers to the frames. If the session is a connection oriented session the frames need to be resembled in the destination. The network layer at the receiving and then assembles all the constituent frames and sends them to the other layers. This layer ensure that all the frames are received property by a method called the cyclic redundancy check (CRC).