The network layer provides communication between the multiple networks. Whereas the data link layer provides the communication between two systems on the same network of two systems are connected to the same link there is usually more need for a network layer. However if the systems are attached to the different networks ( links) with connecting devices there is often a need for the network layer to accomplish sources to destination delivery. It defines addressing and routing ( logical link) between sources and destination. This layer also makes sure that data packets are transmitted across the networks correctly.Other responsibilities of the network layer include the followings.