network layer
The network layer is layer 3 in the OSI reference model. In non-OSI terminology, it is referred to as the network layer. The network layer enables connections to be set up between any two nodes by means of suitable addressing. The functions to be performed for this are: Switching, connection establishment and termination, reset, disconnection, error detection, and transparent data transport between network endpoints.
The functions of the network layer
The basic task of the network layer is to provide services or functions that make it possible to interconnect the secured system connections. In this context, not only homogeneous networks or routing through a single network must be taken into account, but also end-system connections that can be routed through several different networks must be enabled.
The network layer provides various services to the transport layer above it. For example, data units are transported transparently through the network, with care taken to maintain the correct sequence in connection-oriented communication. Flow control allows the terminal or the switching system to control the flow of data during connection-oriented communication between the terminal and the switching system. If a communication partner stops the data flow to its device because it is no longer ready to receive, all data is buffered until the communication partner releases the data flow again. Feature agreements are required by the user to activate various communication functions, such as call forwarding, closed user groups, etc.
The definition of the network layer according to DIN
The definition for the network layer according to DIN is: The network layer links secured data connections (from end system to transit system and between transit systems) to an end system connection (from end system to end system).