OSI, or the Open System Interconnection, is a method of visualizing seven different layers of a network and how that network transmits data. It’s a theoretical concept, but it allows professionals to more clearly explain what certain software or hardware does specifically within a network by identifying certain “layers.” Those layers each perform tasks within network transmissions. They move from the most client-facing to the baseline, starting with number seven.
OSI is also referred to as the OSI reference model or OSI model.
The seven layers of OSI
7. The application layer is the most client-facing layer of the system and manages the most visible communication and authentication in networking.
6. The presentation layer makes data understandable for the application layer and prepares it to be sent over the network.
5. The session layer manages sessions between clients and servers, initiating them and determining their duration.
4. The transport layer manages data packets as they are sent across a network and the correct amount of data so that the system is not overwhelmed.
3. The network layer properly directs data packet transmissions between routers and throughout the network.
2. The data link layer directs data between nodes within a network, passing bits between different points. It also manages the rate of transmission, and it tracks if bits malfunction.
1. The physical layer includes the computer, motherboard, routers, or any other hardware that host a network.
Alternate definitions
OSI also stands for the Open Source Initiative, a non-profit that verifies different open source services.
