TCP/IP and Internet Protocols

The TCP/IP model (Transmission Control Protocol / Internet Protocol) is the practical protocol suite that powers the Internet. Unlike the theoretical OSI model, TCP/IP was designed by implementation — it grew out of real-world networking needs and is the foundation of all modern network communication.

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TCP/IP vs OSI

TCP/IP Layer	OSI Layers	Key Protocols
Application	Application, Presentation, Session	HTTP, HTTPS, DNS, SMTP, FTP, SSH
Transport	Transport	TCP, UDP
Internet	Network	IP (v4/v6), ICMP, ARP
Network Access	Data Link, Physical	Ethernet, Wi-Fi, PPP

The TCP/IP model is simpler (4 layers vs 7) and maps directly to the protocols in use today.

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The Internet Protocol (IP)

IP is the workhorse of the Internet layer. It handles addressing and routing packets from source to destination.

IPv4

• 32-bit address written as four octets: 192.168.1.100
• Approximately 4.3 billion unique addresses (2^32)
• Address exhaustion led to the development of IPv6

IPv6