FREE LESSON · Networks & distributed systems · 1 OF 4
What Happens When You Visit a Website?
One request crosses many protocols — DNS, IP, transport, TLS, and HTTP
Layering lets each protocol solve one part of communication.
Naming maps a service name to reachable addresses. IP forwards packets across networks on a best-effort basis. A transport such as TCP provides an ordered byte stream with flow and congestion control; QUIC builds secure multiplexed streams over UDP. TLS authenticates peers and protects bytes. HTTP defines application messages and semantics.
Each layer assumes services below it and offers a narrower contract above it.
TCP reliability is not application success
TCP can retransmit lost segments and deliver bytes in order. The server may still reject the request, crash after committing it, or send a response the client never receives. Transport reliability protects a stream between endpoints; application correctness needs operation identity and outcome semantics.
A lower-layer acknowledgement is evidence about that layer—not proof that the user’s intention completed.