Communicating via networks

Communication between applications can happen through a network, even if the applications are on the same machine. In order to transfer information, they need to establish a common protocol that specifies what happens all the way from the application to the wire.

OSI model

The Open Systems Interconnect (OSI) model is a theoretical model that dates back to the early 1970s. It defines a standard of communication that works regardless of the physical or technical structure of a network, with the goal of providing interoperability for different networks. 

The model defines seven different layers, numbered from one to seven, and each layer has a higher level of abstraction to the previous...