The OSI model
The seven layers of the OSI model explained with what happens when you open a web page: physical, data link, network, transport, session, presentation and application, the simpler TCP/IP model, encapsulation, which devices and protocols live at each layer, and using the layers to troubleshoot.
CodexBash, , 6 min read
When you type a web address and press Enter, your request passes through a stack of technologies: application code, encryption, a transport protocol, IP addressing, Wi-Fi or Ethernet, and finally radio waves or electrical signals. The OSI model (Open Systems Interconnection) divides that journey into seven layers, each with its own job and its own protocols. Real networks follow the simpler TCP/IP model, but OSI's vocabulary is everywhere: "a layer 4 load balancer", "a layer 7 firewall", "that's a layer 1 problem". This article explains each layer with concrete examples and shows how the model helps you troubleshoot.
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