Glossary

Idempotency

Learn what idempotency means in HTTP. Understand which methods are idempotent and why it matters for retry logic and API design.

Safe Methods

Understand HTTP safe methods — GET, HEAD, OPTIONS, and TRACE. Learn why they matter for crawlers, caches, and API design.

Content Negotiation

Learn about HTTP content negotiation — how clients and servers agree on response format, language, and encoding using Accept headers.

Status Code

What is a status code? Learn about HTTP status code classes (1xx-5xx) and how other protocols use similar numeric response codes.

Reason Phrase

What is an HTTP reason phrase? Learn about status line text like 'Not Found' and why HTTP/2 removed reason phrases.

Media Type (MIME Type)

Understand MIME types and media types — how Content-Type headers identify data formats like text/html and application/json.

Response Header

What are HTTP response headers? Learn about Content-Type, Cache-Control, and other metadata fields servers send with responses.

Request Method (HTTP Verb)

Learn about HTTP request methods (GET, POST, PUT, DELETE, etc.) and their semantics for safety, idempotency, and resource operations.

Redirect

What is an HTTP redirect? Learn about 301, 302, 307, 308 status codes and how Location headers guide clients to new URLs.

Cookie

Understand HTTP cookies — Set-Cookie headers, security attributes like HttpOnly and SameSite, and how cookies enable sessions.

Session

What is an HTTP session? Learn how servers maintain state across stateless HTTP requests using session IDs and cookies.

HTTP/2

What is HTTP/2? Learn about binary framing, multiplexing, HPACK compression, and how HTTP/2 improves performance over HTTP/1.1.

HTTP/3

What is HTTP/3? Learn about QUIC transport, zero-RTT connections, and how HTTP/3 eliminates TCP head-of-line blocking.

REST (Representational State Transfer)

What is REST? Learn about RESTful API design principles, HTTP methods for CRUD operations, and how REST leverages status codes.

GraphQL

What is GraphQL? Learn how this query language differs from REST, uses a single endpoint, and handles errors in the response body.

TLS Handshake

How does a TLS handshake work? Learn about the process of establishing encrypted connections, certificate verification, and TLS 1.3 improvements.

TLS Certificate (SSL Certificate)

What is a TLS/SSL certificate? Learn about digital certificates, Certificate Authorities, and how they enable HTTPS.

CORS (Cross-Origin Resource Sharing)

Understand CORS — Cross-Origin Resource Sharing. Learn how browsers enforce same-origin policy and how servers allow cross-domain requests.

Cipher Suite

What is a cipher suite? Learn about the cryptographic algorithm combinations used in TLS connections for key exchange, encryption, and integrity.

Authentication

HTTP authentication explained — Basic, Bearer, Digest schemes. Understand 401 vs 403 and how authentication works in web protocols.

XSS (Cross-Site Scripting)

What is XSS? Learn about Cross-Site Scripting attacks — stored, reflected, and DOM-based — and defenses like CSP and output encoding.

CSRF (Cross-Site Request Forgery)

What is CSRF? Learn about Cross-Site Request Forgery attacks, how cookies enable them, and defenses like CSRF tokens and SameSite.

SQL Injection

What is SQL injection? Learn how attackers exploit unsanitized inputs to manipulate databases, and how to prevent it.

HSTS (HTTP Strict Transport Security)

What is HSTS? Learn how Strict-Transport-Security forces HTTPS connections and protects against downgrade attacks.

CSP (Content Security Policy)

What is CSP? Learn how Content Security Policy headers prevent XSS attacks by controlling which resources browsers can load.

OAuth 2.0

What is OAuth 2.0? Learn about authorization grant types, access tokens, and how third-party apps access resources securely.

JWT (JSON Web Token)

What is a JWT? Learn about JSON Web Tokens — header, payload, signature structure and use in API authentication.

TCP/IP

TCP/IP fundamentals — how the internet's core protocol suite provides reliable data delivery and packet routing for HTTP, SMTP, and other protocols.

Three-Way Handshake

How does a TCP three-way handshake work? Learn about SYN, SYN-ACK, ACK and how connections are established before HTTP requests begin.

Port Number

What are port numbers? Learn about well-known ports (80, 443, 25, 53) and how they identify network services.

Latency

What is network latency? Learn how delay affects HTTP requests, what causes timeouts (408, 504), and how CDNs reduce latency.

Timeout

Understand network timeouts — connection, read, and gateway timeouts. Learn about HTTP 408 and 504 timeout status codes.

Load Balancer

What is a load balancer? Learn about L4/L7 load balancing, traffic distribution, and related errors like 502 Bad Gateway.

Reverse Proxy

Understand reverse proxies — how Nginx, HAProxy, and CDNs sit between clients and servers, and what causes 502/503/504 errors.

NAT (Network Address Translation)

What is NAT? Learn how Network Address Translation maps private to public IPs and why it complicates peer-to-peer protocols.

Firewall

What is a firewall? Learn about packet filtering, stateful inspection, and WAFs that control network traffic and protect services.

Proxy Server (Forward Proxy)

What is a proxy server? Learn how forward proxies work, differ from reverse proxies, and enable caching and access control.

DNS over HTTPS (DoH)

What is DNS over HTTPS (DoH)? Learn how encrypted DNS queries improve privacy by tunneling through HTTPS on port 443.

IPv6

What is IPv6? Learn about 128-bit addresses, why IPv6 replaces IPv4, and how AAAA records enable the transition.

Subnet (Subnetwork)

What is a subnet? Learn about IP subnetting, CIDR notation, subnet masks, and how networks are divided for performance and security.

Request-Response Model

The request-response model explained — how HTTP, SMTP, FTP, and other protocols structure client-server communication.

RFC (Request for Comments)

What is an RFC? Learn about Request for Comments documents — the formal standards that define HTTP, SMTP, DNS, and other internet protocols.

IANA (Internet Assigned Numbers Authority)

What is IANA? Learn about the Internet Assigned Numbers Authority and its role in maintaining HTTP status codes, port numbers, and protocol registries.

Protocol Upgrade

How does protocol upgrade work? Learn about HTTP 101 Switching Protocols, WebSocket upgrades, and HTTP/2 negotiation.

Multiplexing

What is multiplexing? Learn how HTTP/2 and gRPC send multiple requests simultaneously over a single connection.

Backward Compatibility

What is backward compatibility? Learn why protocols like HTTP/2 and gRPC maintain compatibility with older versions.

Protocol Buffers (Protobuf)

What are Protocol Buffers? Learn about Google's binary serialization format used by gRPC for compact, fast, schema-driven messaging.

Serialization

What is serialization? Learn about JSON, Protobuf, XML, and other formats for converting data for network transmission.

Cache-Control

Master HTTP Cache-Control headers — max-age, no-cache, no-store, public, private. Learn how caching directives improve performance.

ETag (Entity Tag)

What is an ETag? Learn about HTTP entity tags for conditional requests and how 304 Not Modified saves bandwidth.

CDN (Content Delivery Network)

What is a CDN? Learn how Content Delivery Networks cache content globally to reduce latency and improve website performance.

Stale-While-Revalidate

What is stale-while-revalidate? Learn how this Cache-Control directive serves stale content instantly while refreshing in the background.

Cache Invalidation

What is cache invalidation? Learn strategies for keeping cached content fresh — expiration, versioning, purging, and tag-based approaches.

Edge Caching

What is edge caching? Learn how CDN edge servers cache content near users to reduce latency and origin server load.

DNS Resolution

How does DNS resolution work? Learn about the process of translating domain names to IP addresses and DNS response codes (RCODEs).

DNS Record Types

Understand DNS record types — A, AAAA, CNAME, MX, TXT, NS, and more. Learn what each DNS record type does.

TTL (Time to Live)

What is TTL in DNS? Learn about Time to Live values, DNS caching duration, and how TTL affects DNS propagation speed.

DNSSEC (DNS Security Extensions)

What is DNSSEC? Learn how DNS Security Extensions use cryptographic signatures to authenticate DNS responses and prevent tampering.

DNS over TLS (DoT)

What is DNS over TLS (DoT)? Learn how encrypted DNS on port 853 improves privacy while maintaining network visibility.

Anycast

What is anycast? Learn how one IP address serves from multiple global locations to reduce latency and improve DNS resilience.

SMTP Relay

How does SMTP relay work? Learn about email forwarding between servers and SMTP reply codes like 250, 421, and 550.

SPF, DKIM, and DMARC

Understand SPF, DKIM, and DMARC — the three pillars of email authentication that prevent spoofing, phishing, and delivery failures.

Bounce Rate (Email)

What is email bounce rate? Learn about hard vs soft bounces, SMTP error codes, and how bounce rates affect sender reputation.

Email Deliverability

What is email deliverability? Learn how sender reputation, authentication, and SMTP codes determine whether emails reach the inbox.

MTA (Mail Transfer Agent)

What is an MTA? Learn about Mail Transfer Agents like Postfix and Exim that relay email between servers using SMTP.

WebSocket Frame

What is a WebSocket frame? Learn about text, binary, ping/pong, and close frames and WebSocket close status codes.

gRPC Streaming

Learn about gRPC streaming patterns — unary, server streaming, client streaming, and bidirectional streaming with status codes.

SIP Dialog

What is a SIP dialog? Learn about SIP call sessions, INVITE transactions, and response codes like 180 Ringing and 486 Busy Here.

WebRTC (Web Real-Time Communication)

What is WebRTC? Learn how browsers enable peer-to-peer audio, video, and data communication using ICE, DTLS, and SRTP.

Signaling

What is signaling in WebRTC? Learn about SDP offer/answer exchange and how peers coordinate before establishing connections.

ICE Candidate

What is an ICE candidate? Learn about host, server reflexive, and relay candidates used for NAT traversal in WebRTC.