## What is the OSI Model? - A conceptual framework for understanding network communication. - Defines 7 layers, each with specific functions. --- ## Layers of the OSI Model 1. **Physical Layer**: Handles raw data transmission (e.g., cables, switches). 2. **Data Link Layer**: Ensures error-free data transfer between adjacent nodes. 3. **Network Layer**: Manages data routing and addressing (e.g., IP). 4. **Transport Layer**: Ensures reliable data transfer (e.g., TCP/UDP). 5. **Session Layer**: Manages sessions and connections between applications. 6. **Presentation Layer**: Formats and encrypts data for the application layer. 7. **Application Layer**: Provides network services to end-users (e.g., HTTP, SMTP). --- ## Examples of Protocols by Layer - **Physical Layer**: Ethernet, Wi-Fi. - **Data Link Layer**: MAC addresses. - **Network Layer**: IP, ICMP. - **Transport Layer**: TCP, UDP. - **Session Layer**: NetBIOS, RPC. - **Presentation Layer**: SSL/TLS, JPEG. - **Application Layer**: HTTP, FTP, SMTP, SSH, RDP.