The OSI Model
Last updated: 31 OCT 2024.The Open Systems Interconnection (OSI) model is a reference model created by the International Organization for Standardization (ISO) that "provides a common basis for the coordination of standards development for the purpose of systems interconnection." 🔗
The OSI model is considered by some to be antiquated, but can be still used as a troubleshooting framework to start off with. It generally applies to basic networking, but no longer fits the modern networks. An explaination of this can be found at networkworld.com: Why it's time to let the OSI model die. Also, if you enjoy reading RFC's, you can find The Internet Model from the Internet Engineering Task Force.
The OSI Model is broken down into 7 layers:
| Type | Layer | Name | Function | Example |
|---|---|---|---|---|
| Upper Level | 7 | Application | High-level APIs, including resource sharing, remote file access | HTTP, SMTP, FTP |
| 6 | Presentation | Translation of data between a networking service and an application | SSL, TLS, JPEG, MPEG | |
| 5 | Session | Establishment, maintenance and termination of connections | NetBIOS, PPTP | |
| Transport Level | 4 | Transport | Segmentation and reassembly of data | TCP, UDP |
| 3 | Network | Routing of data | IP, ICMP | |
| 2 | Data Link | Physical addressing | MAC, ARP | |
| 1 | Physical | Media, signal and binary transmission | Ethernet, Wi-Fi |