OSI may refer to any of the following:
1. Short for Open System Interconnection, OSI is a network model developed by ISO in 1978 where peer-to-peer communications are divided into seven layers. Each layer performs a specific task or tasks and builds upon the preceding layer until the communications are complete. Below are the purposes of each of the seven layers.
The seven layers in the OSI model are usually displayed in reverse order, with layer 7 listed first (at the top) and layer 1 listed last (at the bottom).
1 - Physical layer - responsible for the electrical, mechanical, and timing across the link.
2 - Data link layer (also known as the link layer) - responsible for transmitting data across a link.
3 - Network layer - responsible for routing information through the network and allowing systems to communicate.
4 - Transport layer - responsible for transferring information between endpoints on the network and deals with errors, such as lost or duplicate packets.
5 - Session layer - responsible for managing a session between two applications.
6 - Presentation layer - responsible for the data formatting and display, allowing for compatibility.
7 - Application layer - responsible for user interaction. An example of an OSI application is the FTAM.