What is defined as a set of rules that allows networked hosts to communicate data in a structured format?

A protocol is defined as a set of rules that allows networked hosts to communicate data in a structured format. It establishes the conventions for exchanging messages between devices, including how the data should be formatted, transmitted, and acknowledged. This ensures that both sender and receiver can understand and process the information being exchanged, regardless of the underlying hardware and software they are using. Well-known examples of protocols include HTTP for web traffic, FTP for file transfers, and TCP/IP for general internet communication.

The other terms, while relevant to networking, do not describe this set of communication rules. A gateway refers to a device that connects different networks, often serving as a translator between network protocols. An interface generally refers to the boundaries and shared communication pathways between different systems or components but does not imply the rules for communication. Network structure refers to the design and layout of a network, including the physical and logical arrangement of nodes but does not define any rules for communication itself.