The Network Layer
The network layer is concerned with getting packets from the source to the destination. Thus, the network layer has to know about the topology of the network; that is, how the nodes are connected together.
Packets are the unit of information of hte network layer.
Number 3 The OSI Model
The Open Systems Interconnection model (OSI model) is a reference model from the International Organization for Standardization (ISO) that provides a common basis for the coordination of standards development for the purpose of systems interconnection. [2] In the OSI reference model, the communications between systems are split into seven different abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.[3]