3. Network Layer

               The network layer has two main functions. One is breaking up segments into network packets, and reassembling the packets on the receiving end. The other is routing packets by discovering the best path across a physical network. The network layer uses network addresses (typically Internet Protocol addresses) to route packets to a destination node.        

Some protocol use- IP, RARP, ARP, ICMP

• Segment in Network layer is referred as Packet. 

• Network layer is implemented by networking devices such as routers.