Network Layer. In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers, whereas the data link layer is responsible for media access control, flow control and error checking. Functions The network layer provides the functional and procedural means of transferring variable-length data sequences from a source to a destination host via one or more networks, while maintaining the quality of service functions. Functions of the network layer include: Connection model: connectionless communication For example, IP is connectionless, in that a datagram can travel from a sender to a recipient without the recipient having to send an acknowledgement. Host addressing Every host in the network must have a unique address that determines where it is. Message forwarding Protocols Relation to TCP/IP model See also References Tanenbaum, Andrew S. (2003).