Layer	Notes
Application (Layer 7)	Supports applications and end-user processes.
Presentation (Layer 6)	Transforms data into a form the application can accept. Formats data for movement across the network.
Session (Layer 5)	Establishes, manages and terminates connections between applications.
Transport (Layer 4)	Transparent transfer of data between end systems. End to end error recovery and flow control.
Network (Layer 3)	Switching and routing, creating logical paths (virtual circuits) for moving data from node to node.  Congestion control, packet sequencing.
Data Link (Layer 2)	Furnishes transmission protocol knowledge and management and handles errors in the physical layer, flow control and frame synch.
Physical (Layer 1)	Moves electrical impulses, light or radio signals through the network at a mechanical level. Defines cables, cards and their physical features.

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