Back to Knowledge Base
networkingNODE: #osi-model

Open Systems Interconnection (OSI) Model

A 7-layer conceptual framework developed by ISO to standardize telecommunication and computer network communication.

AKA:OSI, 7-layer OSI model, OSI reference model
#networking#architecture#fundamentals#standards
GRAPH_RELATIONS // CONNECTED_NODESLINKED
CONTAINS:
↳OSI Layer 7: Application Layer↳OSI Layer 6: Presentation Layer↳OSI Layer 5: Session Layer↳OSI Layer 4: Transport Layer↳OSI Layer 3: Network Layer↳OSI Layer 2: Data Link Layer↳OSI Layer 1: Physical Layer
RELATED TO:
↳TCP/IP Protocol Suite (Internet Model)

Open Systems Interconnection (OSI) Model

Overview

The OSI Model (ISO/IEC 7498-1) is a conceptual framework that divides network communication into seven distinct layers. Each layer serves the layer above it and is served by the layer below it.

The 7 Layers (Top to Bottom)

  1. Layer 7: OSI Layer 7: Application Layer - User-facing network services (HTTP, DNS, SSH, SMTP).
  2. Layer 6: OSI Layer 6: Presentation Layer - Data formatting, encryption, and compression (TLS, JPEG, ASCII).
  3. Layer 5: OSI Layer 5: Session Layer - Session establishment, management, and termination (RPC, NetBIOS, SOCKS).
  4. Layer 4: OSI Layer 4: Transport Layer - End-to-end delivery, reliability, and flow control (TCP, UDP).
  5. Layer 3: OSI Layer 3: Network Layer - Packet forwarding, logical addressing, and routing (IP, ICMP, BGP).
  6. Layer 2: OSI Layer 2: Data Link Layer - Node-to-node framing, physical addressing, and error detection (Ethernet, Wi-Fi, MAC).
  7. Layer 1: OSI Layer 1: Physical Layer - Electrical, optical, or radio signal transmission of raw bitstreams (Cables, Fiber, Hubs).

Data Encapsulation Hierarchy

As data moves down the stack during transmission:

  • Data (L7-L5) $\to$ Segment (L4) $\to$ Packet (L3) $\to$ Frame (L2) $\to$ Bits (L1)

Comparison with TCP/IP

While the OSI model is a 7-layer theoretical reference standard, modern internet architecture is built on the practical 4-layer TCP/IP Protocol Suite (Internet Model).

← All Knowledge TopicsBack to top ↑