protocol

A protocol is a formal set of rules and conventions for how entities communicate, interact, or perform a task. Protocols specify the syntax (structure of messages), semantics (meaning), synchronization, and error handling. They can govern technical communications among computers, as well as procedures in diplomacy, science, and other fields.

In computing and networking, a protocol defines how data is formatted, transmitted, compressed, encrypted, and verified for integrity. Examples include HTTP for web requests, TCP for reliable transport, IP for addressing, and SMTP for email. Protocols are often organized into layers (for example, the OSI or TCP/IP models) to separate concerns such as application, transport, and network functions.

A protocol also describes the sequence of interactions between communicating parties, including handshakes, acknowledgments, and timers, to achieve reliable exchange. Compatibility and interoperability require adherence to the documented rules, and deviations can cause miscommunication or failures.

In diplomacy and ceremonial settings, protocol governs etiquette, order of precedence, and formal procedures for ceremonies, correspondence, and official visits.

In science and research, a protocol is a predefined experimental or clinical procedure intended to ensure consistency and reproducibility.

Protocols are formalized in standards documents produced by organizations such as the IETF, ISO, and ITU, and implemented by software and hardware that must interoperate. Security considerations, including authentication and encryption, are integral to many protocols to protect data and verify identities.