Understand the Protocols
That Power Everything
From factory floors to web browsers, protocols define how devices communicate. We break them down with clear explanations, visual diagrams, and real-world context.
Protocol Guides
Pick a protocol to get a complete breakdown with diagrams, examples, and FAQs.
Transport Protocols
The core transport layer protocols that deliver data across networks
TCP
Reliable, ordered delivery for the internet. The transport protocol behind HTTP, SSH, and most networked applications.
UDP
Fast, connectionless transport. The lightweight protocol powering DNS, gaming, streaming, and HTTP/3.
Security Protocols
Encryption and authentication protocols that secure internet communication
TLS
The encryption layer that secures HTTPS, email, and more. TLS 1.3 is the current standard for internet security.
SSL
The deprecated predecessor to TLS. Understand its history, vulnerabilities, and why it was replaced.
IPsec
Network-layer VPN and encryption. Secures all IP traffic transparently with tunnel and transport modes, used in site-to-site and remote access VPNs.
Network Protocols
Network layer protocols for diagnostics and error reporting
ICMP
The diagnostic protocol behind ping and traceroute. Essential for network troubleshooting and error reporting.
ARP
Maps IP addresses to MAC addresses on local networks. Every Ethernet device uses ARP to deliver packets to the right destination.
DHCP
Automatic IP address assignment for every device on the network. The DORA process configures devices in milliseconds.
NAT
Translates private IPs to public IPs so many devices can share a single internet address. Every home router uses NAT.
Routing Protocols
Protocols that determine how data finds its path across networks and the internet
BGP
The routing protocol that holds the internet together. Exchanges routes between ISPs and large networks via AS path selection.
OSPF
The most widely used interior gateway protocol. Link-state routing with Dijkstra's SPF algorithm and area-based scalability.
Web Protocols
Protocols that power the internet and web applications
HTTP
The foundation of the web. The protocol behind every web page, API call, and file download.
HTTPS
HTTP secured with TLS encryption. The standard for safe, authenticated web communication.
WebSocket
Full-duplex communication over a single TCP connection. The protocol behind real-time chat, live dashboards, and collaborative editing.
Application Protocols
Protocols for remote access, email, messaging, and network services
DNS
The phonebook of the internet. Translates domain names like example.com into IP addresses.
SSH
Encrypted remote access and tunneling. The protocol that replaced Telnet for secure server administration.
SMTP
The protocol that delivers email across the internet. Every email you send uses SMTP.
IMAP
Email sync across all your devices. IMAP keeps messages on the server with full folder management and push notifications.
POP3
Download-and-delete email retrieval. Simple protocol for single-device email access with full offline support.
MQTT
Lightweight pub-sub messaging for IoT. The standard protocol for sensor networks, smart homes, and connected devices.
Telnet
Legacy plaintext remote access. Understand why it was replaced by SSH and where it still appears today.
FTP
File transfer over dual channels. One of the oldest internet protocols, still found in legacy systems.
NTP
Network time synchronization. Keeps clocks accurate across the internet using a stratum hierarchy.
SNMP
Network device monitoring and management. GET, SET, and TRAP operations for routers, switches, and servers.
RTP
Real-time audio and video delivery over UDP. The protocol behind VoIP calls, video conferencing, and live streaming.
TFTP
Trivially simple file transfer over UDP. The go-to protocol for PXE network booting and firmware updates.
LDAP
The directory services protocol behind Active Directory, corporate authentication, and identity management.
gRPC
High-performance RPC framework built on HTTP/2 and Protocol Buffers. The standard for microservice communication at Google, Netflix, and Dropbox.
SNTP
Simplified time synchronization for embedded systems and IoT devices. Same packet format as NTP with minimal implementation overhead.
SIP
The signaling protocol behind every VoIP call. SIP sets up, manages, and tears down voice and video sessions while RTP carries the media.
Industrial Protocols
Protocols used in manufacturing, automation, and SCADA systems
PROFINET
Real-time industrial Ethernet by Siemens. RT and IRT communication for factory automation and motion control.
EtherNet/IP
CIP over standard Ethernet. The dominant industrial protocol in North America for discrete manufacturing.
Modbus RTU
Serial communication protocol for industrial devices. The backbone of SCADA systems worldwide.
Modbus TCP
Modbus over TCP/IP networks. Brings industrial communication to modern Ethernet infrastructure.
CAN Bus
The robust serial bus protocol for automotive and embedded systems. Priority-based arbitration with no collisions.
Wireless Protocols
Low-power wireless protocols for IoT, smart home, and sensor networks
Zigbee
Low-power mesh networking for smart home devices. Self-healing topology with up to 65,000 nodes.
LoRaWAN
Long-range, low-power wide-area networking for IoT. Reaches up to 15 km on coin-cell batteries with star-of-stars architecture.
What Is a Protocol?
A protocol is a set of rules that defines how data is formatted, transmitted, and received between devices. Think of it as a language that machines agree to speak so they can understand each other.
Control how data is delivered between devices. TCP provides reliable, ordered delivery while UDP offers fast, lightweight transmission.
TCP, UDP
Encrypt and authenticate communication to protect data in transit. TLS is the current standard, while SSL is its deprecated predecessor.
TLS, SSL, IPsec
Handle network-layer functions: IP address assignment, address translation, diagnostics, and error reporting. Essential infrastructure for every network.
ICMP, ARP, DHCP, NAT
Determine how packets find the best path across networks. BGP routes between ISPs on the internet, while OSPF routes within a single organization.
BGP, OSPF
Power the World Wide Web. HTTP defines how browsers and servers communicate, and HTTPS adds encryption via TLS.
HTTP, HTTPS, WebSocket
Serve specific application needs: name resolution (DNS), remote access (SSH), email delivery (SMTP), IoT messaging (MQTT), and more.
DNS, SSH, SMTP, IMAP, POP3, MQTT, FTP, NTP, SNMP, RTP, TFTP, LDAP, gRPC, SNTP, SIP, Telnet
Enable communication between PLCs, sensors, drives, and SCADA systems in factories, power plants, and building automation.
PROFINET, EtherNet/IP, Modbus RTU, Modbus TCP, CAN Bus
Low-power wireless protocols for IoT, smart home, and sensor networks. Mesh topologies provide range extension and self-healing connectivity.
Zigbee, LoRaWAN
Why justprotocols?
Protocol documentation is often dense, dry, and hard to follow. We do it differently.
Visual Diagrams
Every protocol includes custom SVG diagrams showing frame structures, handshake flows, and architecture. No walls of text.
Easy to Digest
Complex protocols broken down into short sections with clear headings, comparison tables, and FAQ sections. No prior knowledge required.
Real-World Context
Learn where each protocol is actually used, from factory floors and SCADA systems to web browsers and REST APIs.