Application Layer Protocols
Run a Speed TestEvery application on the internet communicates using a protocol — a defined set of rules for how data is formatted, exchanged, and interpreted. These guides explain how SSH, FTP, SMTP, HTTP/2, WebSockets, VoIP, and every other major application layer protocol works, why each exists, and when to use each one.
Remote Access Protocols
What Is SSH?
Secure Shell — how SSH encrypts remote terminal sessions, authenticates with keys, and replaced Telnet.
SSH vs Telnet
Why Telnet sends everything in plaintext and SSH replaced it — encryption, authentication, and port differences.
What Is RDP?
Remote Desktop Protocol — how Microsoft's RDP streams a full graphical desktop over a network connection.
What Is VNC?
Virtual Network Computing — how VNC shares a desktop across platforms and how it compares to RDP.
File Transfer Protocols
What Is FTP?
File Transfer Protocol — how FTP's dual-channel design works, its security weaknesses, and why SFTP replaced it.
FTP vs SFTP vs FTPS
Three file transfer protocols with very different security models — which to use and why FTP alone is never appropriate.
What Is SFTP?
SSH File Transfer Protocol — how SFTP tunnels file transfers securely over SSH on port 22.
What Is SCP?
Secure Copy Protocol — how SCP transfers files over SSH and when to use SCP vs SFTP vs rsync.
Email Protocols
What Is SMTP?
Simple Mail Transfer Protocol — how email travels from sender to recipient through SMTP relays and MX records.
IMAP vs POP3
Server-synced email vs download-and-delete — why IMAP won for multi-device access and when POP3 still makes sense.
What Is IMAP?
Internet Message Access Protocol — how IMAP keeps email synchronized across all your devices in real time.
Web Protocols
What Is HTTP?
The web's request-response protocol — methods, status codes, HTTPS, caching, and how HTTP/2 and HTTP/3 changed performance.
HTTP/2 vs HTTP/3
How HTTP/2 multiplexing over TCP compares to HTTP/3 over QUIC — head-of-line blocking, 0-RTT, and real-world speed.
What Is QUIC?
Google's UDP-based transport that became the backbone of HTTP/3 — connection migration, 0-RTT handshake, and stream multiplexing.
What Is WebSocket?
How WebSockets upgrade an HTTP connection to a persistent, full-duplex channel — enabling real-time apps, chat, and live feeds.
What Is gRPC?
Google's Remote Procedure Call framework — Protocol Buffers, HTTP/2 streaming, and how gRPC compares to REST.
Real-Time and Messaging Protocols
What Is VoIP?
Voice over IP — how phone calls travel as data packets, what determines call quality, and why latency matters more than bandwidth.
What Is SIP?
Session Initiation Protocol — how SIP sets up, manages, and tears down VoIP calls and video sessions.
What Is WebRTC?
How browsers create low-latency voice, video, screen sharing, and data connections using ICE, STUN, TURN, and SRTP.
What Is MQTT?
Message Queuing Telemetry Transport — the lightweight publish/subscribe protocol behind IoT sensors and smart home devices.
What Is NTP?
How Network Time Protocol keeps clocks synchronized across servers, routers, and network devices.
What Is SNMP?
Simple Network Management Protocol — how routers and switches expose monitoring data to management tools.
What Is SMB?
Server Message Block — the Windows file sharing protocol, and why SMB1 is dangerous.
What Is NFS?
Network File System — how Linux and NAS systems share directories over the network.
What Is RTSP?
Real Time Streaming Protocol — how IP cameras and video servers stream live footage.