What is the function of the Network Layer of the OSI model?

The Network Layer is primarily concerned addressing and routing. Logical addresses (e.g., an IP address) are translated into physical addresses (i.e., the MAC address) for transmission at the network layer. On the receiving side, the translation process is reversed.

It is at the network layer where the route from the source to destination computer is determined. Routes are determined based on packet addresses and network conditions. Traffic control measures are also implemented at the network layer.

Common protocols that operate at this level include IP, IPX, and X.25 (frame relay).