Networking & Protocols

A numerical label assigned to each device on a network. IPv4 uses 32-bit dotted-decimal notation (192.168.1.1); IPv6 uses 128-bit hex.

"The service binds to 0.0.0.0 to accept connections on all network interfaces, but only 127.0.0.1 for local-only access."

Domain Name System — the distributed system that translates human-readable domain names (api.example.com) into IP addresses.

"DNS propagation took 10 minutes after we updated the A record — until then, some users still resolved the old IP."

HyperText Transfer Protocol — the request/response protocol for web communication. HTTPS adds TLS encryption.

"All API traffic is HTTPS-only — the load balancer terminates TLS and forwards plain HTTP to the backend over the private network."

TCP (Transmission Control Protocol) is reliable, ordered, and connection-based. UDP is faster but unordered and connectionless.

"We use TCP for API calls where data integrity matters. WebRTC video uses UDP — a dropped frame is better than waiting for a retransmit."

Transport Layer Security — a cryptographic protocol that provides encryption, authentication, and integrity for data in transit (successor to SSL).

"TLS termination at the load balancer means the certificate is managed in one place and internal traffic stays on the private VPC network."

A component that distributes incoming network traffic across multiple backend servers to improve reliability and throughput.

"The load balancer uses round-robin to distribute requests across our three API servers — if one fails health checks it's removed automatically."

Content Delivery Network — a distributed network of servers that caches and serves static assets from locations close to users.

"We push our static JS and image assets to a CDN — users in Tokyo get files from a Singapore edge node, not our US-East origin."

A forward proxy sits in front of clients; a reverse proxy sits in front of servers. Nginx and HAProxy are common reverse proxies.

"Nginx acts as a reverse proxy — it receives all requests, terminates TLS, and forwards to the appropriate microservice."

A protocol providing full-duplex communication over a persistent TCP connection, initiated via HTTP upgrade handshake.

"The real-time chat uses WebSockets — once the connection is established, the server pushes messages to clients without polling."

2xx = success, 3xx = redirect, 4xx = client error, 5xx = server error. Common: 200 OK, 201 Created, 400 Bad Request, 401 Unauthorized, 404 Not Found, 429 Too Many Requests, 500 Internal Server Error.

"The API returns 422 Unprocessable Entity for validation errors — 400 and 422 both indicate client error, but 422 is semantically richer."

The delay between sending a request and receiving a response, typically measured in milliseconds. Affected by distance, routing, and processing time.

"p99 latency spiked to 2.4 seconds during the incident — the 99th percentile matters more than average for user experience."

The maximum rate of data transfer across a network link, measured in bits per second (Mbps, Gbps).

"Video streaming is bandwidth-intensive — we encode at multiple bitrates so users on slow connections get a lower-quality stream."

A network security device that monitors and controls incoming and outgoing traffic based on configurable rules.

"The firewall rules only allow inbound traffic on ports 80 and 443 — all other ports are blocked at the network level."

Virtual Private Cloud — an isolated virtual network within a cloud provider where you launch resources with full control over IP ranges, subnets, and routing.

"The database is in a private subnet of the VPC — it has no public IP and can only be reached from within the VPC."

Controlling the rate of requests a client can make to an API within a time window to prevent abuse and ensure fair usage.

"The public API enforces rate limiting at 100 requests per minute per API key — clients exceeding this receive a 429 response."