OSI Model
The Open Systems Interconnection (OSI) model is a reference tool for understanding data communications between any two networked systems. It divides the communications processes into seven layers. Each layer both performs specific functions to support the layers above it and offers services to the layers below it.
Physical Layer
Data Link
- MAC Addressing
- Flow control
- Error control: Error detection, followed by correction and/or re-transmition.
- Line discipline
- Unit of measure: Frames
Network
- IP Addressing
- Unit of measure: Packets
Transport
- Responsible for providing and managing end-to-end transmission of messages between two end nodes.
- Maps transport and network addresses, port-based.
Protocols
- TCP: Reliable transfer and guarantees error-free delivery of data in the correct order.
- UDP: "Unreliable" transport, no sequence messages.