OSI vs TCP/IP Models
1. Introduction
1.2. TCP/IP Model:
Layers: Four layers (Link, Internet, Transport, Application).
Nature: Practical protocol suite, implemented to support the internet and real-world networks.
Granularity: Streamlined, combining OSI’s upper three layers (Session, Presentation, Application) into a single Application layer.
Development: Evolved from ARPANET research, designed for interoperability and internet functionality.
2. Layer Mapping
The TCP/IP model’s four layers correspond to the OSI model’s seven layers as follows:
OSI Layer | TCP/IP Layer | Description |
Physical (1) | Link | OSI’s Physical layer (bit transmission, cables) is combined with Data Link in TCP/IP’s Link layer. |
Data Link (2) | Link | OSI’s Data Link layer (framing, MAC addressing) is part of TCP/IP’s Link layer (e.g., Ethernet, Wi-Fi). |
Network (3) | Internet | OSI’s Network layer (routing, IP addressing) directly maps to TCP/IP’s Internet layer (e.g., IP). |
Transport (4) | Transport | OSI’s Transport layer (reliable/unreliable delivery, ports) aligns with TCP/IP’s Transport layer (e.g., TCP, UDP). |
Session (5) | Application | OSI’s Session layer (session management) is absorbed into TCP/IP’s Application layer. |
Presentation (6) | Application | OSI’s Presentation layer (data formatting, encryption) is part of TCP/IP’s Application layer. |
Application (7) | Application | OSI’s Application layer (user services) is included in TCP/IP’s Application layer (e.g., HTTP, DNS). |