Figure lists the seven layers of the OSI model and a brief description of what each layer provides.  The layers from top down are as follows. Layer seven is the application layer which provides the means for end-to-end connectivity between individuals in the human network using data networks.  Layer six is the presentation layer which provides for common representation of the data transferred between application layer services.  Layer five is the session layer which provides services to the presentation layer to organize its dialogue and to manage data exchange.  Layer four is the transport layer which defines services to segment, transfer, and reassemble the data for individual communications between the end devices.  Layer three is the network layer which provides services to exchange the individual pieces of data over the network between identified end devices.  Layer two is the data link layer, and protocols here describe methods for exchanging data frames between devices over a common media.  Layer one is the physical layer and protocols here describe the mechanical, electrical, functional, and procedural means to activate, maintain, and de-activate physical-connections for bit transmission to and from a network device.