ip-protocol

Devices on different networks need to address and route packets across multiple hops. Link-layer protocols only work within a single network, so a network-layer protocol is needed for internetwork communication.

The fundamental network-layer protocol that provides logical addressing (IP addresses) and routing packets across networks from source to destination.

1. Assigns logical IP addresses to devices (IPv4: 32-bit, IPv6: 128-bit)
2. Each packet contains source and destination IP addresses
3. Routers examine destination IP and forward packets toward destination
4. Connectionless and unreliable: best-effort delivery without guarantees
5. TTL (Time To Live) field prevents packets from looping forever

• Connectionless: each packet routed independently
• Unreliable: no delivery guarantees, no error recovery
• Provides logical addressing and routing
• Foundation of the internet protocol suite

• Built from: Connectionless Service — IP is connectionless
• Builds into: TCP — runs on top of IP
• Builds into: UDP — runs on top of IP
• Related: Routing — how routers forward IP packets
• Related: IPv4 and IPv6 — protocol versions

• Fragmentation can occur when packet exceeds MTU (Maximum Transmission Unit)
• NAT (Network Address Translation) complicates end-to-end addressing
• IPv4 address exhaustion led to IPv6 development