Network layer protocols

The network layer is responsible for enabling the communication between networks. It provides the routing mechanism, and so logical elements such as IP addressing and routing protocols come into play. The term packet is used to represent the PDU at this layer, as shown in Figure 2.11. In this layer, the following communication protocols operate:

• IP
• ICMP
• IPSec
• NAT
• RIP operates on port 520
• OSPF