Open Systems Interconnection (OSI) is a seven-layer model that explains how devices communicate over a network. Each layer handles a different part of network communication.

The model helps people understand how data moves between devices. Network professionals also use it to identify where a network problem may occur.

The Seven Layers

1. Physical: Sends raw signals through cables, fiber or wireless connections.
2. Data Link: Handles communication between devices on the same network.
3. Network: Handles IP addresses and routing between networks.
4. Transport: Controls how data is delivered between devices.
5. Session: Manages communication sessions between applications.
6. Presentation: Handles data formatting, encryption and compression.
7. Application: Provides network services used by applications.

Common Uses

• Learning how computer networks work.
• Troubleshooting network problems.
• Understanding network protocols.
• Designing and managing networks.
• Teaching networking concepts.

Related Terms: Network Layer, Transport Layer, Data Link Layer, Physical Layer, TCP/IP, Network Protocol, IP Address, Ethernet, Routing, Protocol Stack

Related Entries

• Protocol Stack
• ARP
• Connectionless Protocol
• Router
• Auto-Negotiation