|  |  | Overview
The network layer is responsible for navigating the data through the network. The function of the network layer is to find the best path through the network. The network layer's addressing scheme is used by devices to determine the destination of data as it moves through the network. In this chapter, you will learn about the router’s use and operations in performing the key internetworking function of the Open System Interconnection (OSI) reference model’s network layer, Layer 3. In addition, you will learn about IP addressing and the three classes of networks in IP addressing schemes. You also will learn that some IP addresses have been set aside by the American Registry for Internet Numbers (ARIN) and cannot be assigned to any network. Finally, you will learn about subnetworks and subnet masks and their IP addressing schemes.