---
id:"kb-2026-00184"
title:"OSI Model"
schema_type:"TechArticle"
category:"computer-science"
language:"en"
confidence:"high"
last_verified:"2026-05-22"
generation_method: "human_only"
ai_models:["claude-opus"]
derived_from_human_seed:true


known_gaps:
  - "Sources reconstructed during quality audit; primary source details were corrupted during batch generation"

completeness: 0.88
ai_citations:
  last_citation_check:"2026-05-22"
primary_sources:
- title: "ACM Digital Library"
    type: "repository"
    year: 2026
    url: "https://dl.acm.org/"
    institution: "ACM"
secondary_sources:
  - title: "ACM Digital Library"
    type: "repository"
    year: 2026
    url: "https://dl.acm.org/"
    institution: "ACM"
---

## TL;DR

The OSI (Open Systems Interconnection) model describes 7 layers of network communication. While not literally implemented, it's the standard mental model for understanding networking. Layers: Physical, Data Link, Network, Transport, Session, Presentation, Application.

## Core Explanation

Layer 1: cables, radio, bits on wire. Layer 2: MAC addresses, switches. Layer 3: IP addresses, routers. Layer 4: TCP/UDP, ports. Layers 5-7: often merged in TCP/IP model. TCP/IP model (4 layers): Link, Internet, Transport, Application — simpler, maps directly to real implementations.

## Further Reading

- [undefined](undefined)