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TCP/IP 4-Layer Model

2026-05-12NetworkingProtocolsFundamentalsArchitecture

The network model that actually shipped. How four layers — Link, Internet, Transport, Application — carry every byte your services send, and why every architecture decision you make is secretly a layer decision.

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Engineering Notes

TCP/IP won because it was built from running code, not committee consensus. RFC 1122 mapped it to OSI to prove compatibility, then the internet scaled around it. Every architecture decision you make — NLB vs ALB, TLS termination point, service mesh placement — is a layer decision in disguise.

Why Architects Need This

◆Protocol selection (TCP vs UDP vs QUIC) is a latency/reliability trade-off

◆Infrastructure placement (ALB, WAF, NLB) depends on which layer you operate at

◆Security posture is defined by where you segment and inspect traffic

◆Connection costs (handshake, TLS) compound at scale — understanding them prevents surprises

◆Service mesh (Istio, Envoy) operates at L4/L7 — knowing the model tells you what it sees

Related Concepts

◆OSI Model

◆HTTP/2 & HTTP/3

◆TLS / Encryption

◆Sockets

◆Load Balancers

◆Service Mesh