Layer 3. The Network Layer

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This layer handles how data is routed from the source computer to the destination computer, sending it in the right direction over the correct intermediate nodes to the proper destination, and receiving incoming transmissions at the packet level. The Network Layer does routing and forwarding within and between individual networks and provides a Connection Oriented Network Service (CONS) or a Connectionless Network Service (CLNS). No matter what the route of the actual connection, the data arrives at the destination as if the two data entities were directly connected. It is at this layer that network net traffic problems are managed such as Quality of Service (QoS) and Type of Service (TOS). Devices operating at this layer include routers, brouters (a combination bridge and router), and Layer-3 switches. Protocols working in this layer include ARP, DLC, ICMP, IP, IPX, NetBEUI and RARP. Routing Protocols at this level include BGP, EGP, EIGRP, IGMP, IGRP, OSPF, and RIP.

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