Layer 3 of the OSI model. Operates in the networks (probably routers), not in end stations. Responsible for delivering packets from a source host to a destination host across multiple networks. Provides addressing and routing mechanisms that allow packets to travel through intermediate routers.
Key functions:
- Addresses hosts and network devices.
- Establishes, maintains and terminates connection between hosts.
- Determintes the path packets take through the network
Protocols
In the network layer:
- Routing protocols such as RIP, Border Gateway Protocol and OSPF are used
- IP is used to address hosts.
- ICMP is used for error reporting and inter-router communication.
Internet Layer
The network layer of the Internet responsible for packet delivery across networks. The Internet uses essentially a single network-layer protocol (IP), unlike layered alternatives.
Addressing
The process of identifying end systems within a network so packets can be delivered to the correct destination. Done in many layers such as physical, data-link, network, application layers.
2 types.
Hierarchical Addressing
Addresses structured into multiple levels. Contains multiple components. Enables scalable routing.
Hierarchical addressing simplifies routing by grouping destinations.
Flat Addressing
Addresses without hierarchical structure. No embedded location information.