Network Layer
The Network layer performs the switching and routing of data through the network, controls the flow of data within the network, segments (divides) or reformats data packets if necessary between network types, and performs error control functions specific to the address decoding and routing functions. The network layer receives data for transmission from an upper layer (such as a transport or session layer) and converts it into network addressable data formats that can be transferred through a network or transmission line. An upper layer provides the network layer with the necessary addressing and network routing control requirements (e.g. priority codes) to allow the network layer to send data through the network. The location of the network layer within the protocol stack is usually above a physical layer and below a transmission or session layer. The network layer is layer 3 in the open system interconnection (OSI) protocol layer model.