A protocol is a set of rules governing data exchange between systems. It defines how devices format, send, and receive data. Without protocols, computers would be like people speaking different languages with no translator. Protocols make communication possible.

The internet runs on TCP/IP. The web runs on HTTP. Email uses SMTP and IMAP. File transfer uses FTP. Each protocol defines message formats, sequence, and error handling. Some are open standards. Others are proprietary. Some are simple. Others are complex.

Common protocols

• TCP/IP: internet communication
• HTTP/HTTPS: web browsing
• SMTP/IMAP: email
• DNS: domain name resolution
• DHCP: automatic IP assignment
• MQTT: IoT messaging

Protocols are layered. The OSI model describes seven layers, from physical cables to applications. Each layer has its own protocols. A packet travels down the stack, across the network, and up the other side. The layers hide complexity. You do not need to know how Ethernet works to send an email.