Internet Protocol governs data packets on the internet. It defines how packets are addressed, routed, and delivered. Every device on the internet has an IP address. Every packet has a source and destination address. Routers read those addresses and forward packets toward their destination. IP is the foundation of the internet.

There are two versions. IPv4 uses 32-bit addresses. It has about 4.3 billion possible addresses. That ran out. IPv6 uses 128-bit addresses. It has virtually unlimited addresses. Adoption is growing but not complete. Many networks run both versions.

IP characteristics

• Connectionless: no dedicated path
• Best effort: no guarantee of delivery
• Packet-based: data is split into packets
• Address-based: each packet has source and destination
• Layered: works with TCP for reliability

IP does not guarantee delivery. Packets can be lost, duplicated, or arrive out of order. TCP handles those problems. IP just routes. It is simple, scalable, and robust. That simplicity is why it won. The internet runs on IP. Everything else builds on it.