Network layer messages are termed as packets.

They facilitate the transportation of packets from one end system to another and help to determine the best routes that messages should take from one end system to another.

Routing protocols are applications that run on the network layer and exchange messages with each other to develop information that helps them route transport layer messages.

Load Balancing There are many links (copper wire, optical fiber, wireless) in a given network and one objective of the network layer is to keep them all roughly equally utilized. Otherwise, if some links are under-utilized, there will be concerns about the economic sense of deploying and managing them.