The network layer, or layer 3, has two key roles: addressing and routing data. This layer provides addressing using a logical IP address. While the transport layer transports the data, the network layer determines the best logical path to take for packets that travel through other networks, so they can get to their destination. It does this by communicating with other devices during the routing process.

In addition to data forwarding, the network layer communicates errors in transmission. In order to achieve this, the network layer has a few key protocols, as we will see in the following section.