Networking

Network models split communication into layers, each solving one problem and relying only on the layer below, so a web request becomes nested envelopes: HTTP inside TCP inside IP inside an Ethernet or Wi-Fi frame.

TCP delivers every byte reliably and in order at the cost of extra round trips; UDP just sends packets fast and leaves reliability to the application.

HTTP is the request-response language of the web (a method, a path, headers and a body in; a status code, headers and a body out), and HTTPS is the same HTTP sent inside an encrypted TLS connection.

REST exposes many resource URLs and uses HTTP methods and status codes for meaning, while GraphQL exposes one endpoint with a typed schema where the client asks for exactly the fields it needs.

DNS is the internet's distributed, heavily cached phone book that turns names like example.com into IP addresses by asking root, TLD and authoritative servers in turn.

TLS uses certificates and a key exchange to prove the server's identity and agree on a fresh shared key, then encrypts and authenticates every byte with fast symmetric encryption.

A load balancer spreads incoming requests across many healthy servers using an algorithm such as round robin or least connections, so the service scales horizontally and survives server failures.

A CDN keeps copies of your content on servers in hundreds of cities so users are served from somewhere nearby, cutting latency and taking most of the load off your origin.

WebSockets upgrade one HTTP connection into a long-lived, two-way channel so the server can push messages instantly, instead of the client repeatedly asking whether anything changed.