this layer and the user interact directly with software application that implements a component of communication between the client and server.

establishes data formatting and data translation into a format specified by the application layer during the encapsulation of outgolng messages while being passed down the provides the functional and procedural means of transferring packets from one node to another connected in "different networks".

creates the setup, controls the connections, and ends the teardown, between two or more computers.

provides node$-$to$-$node data transfer$-$a link between two directly connected nodes.

provides the functional and procedural means of transferring variable$-$length data sequences from a source host to a destination host from one application to another across responsible for the transmission and reception of unstructured raw data between a device, such as a network interface controller, Ethernet hub, or network switch, and a phy Internet Layer