Computer Network

A computer network is a system that connects multiple computers and devices with independent functions across different geographical locations through communication lines.

Core Concepts

1. Network Layer Models

• OSI 7-Layer Model: Physical, Data Link, Network, Transport, Session, Presentation, Application.
• TCP/IP 4-Layer Model: Network Interface, Internet (IP), Transport (TCP/UDP), Application (HTTP/FTP/DNS).

2. Key Protocols

• HTTP/HTTPS: Hypertext Transfer Protocol, the foundation of the web.
• TCP (Transmission Control Protocol): Connection-oriented, reliable transport (3-way handshake).
• UDP (User Datagram Protocol): Connectionless, best-effort transport.
• IP (Internet Protocol): Responsible for packet routing and addressing.

3. Network Fundamentals

• IP Addressing: IPv4 and IPv6.
• Domain Name System (DNS): Resolving domain names to IP addresses.
• Routing & Switching: Mechanisms for forwarding data packets across networks.

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The Internet is essentially a collection of protocols.