Which of the following best defines a network protocol?

A network protocol is best defined as a set of rules for data communication. This definition captures the essential function of network protocols, which govern how data is transmitted and received over a network. These rules cover various aspects such as how messages are formatted, how to initiate and terminate communication sessions, how error handling is managed, and how to ensure reliable delivery of data.

In the context of computer networks, protocols are crucial because they establish the standards that enable different devices and applications to communicate effectively regardless of their underlying hardware or software differences. Examples of common network protocols include HTTP for web communication, FTP for file transfers, and TCP/IP for internet communication.

The other options do not accurately represent the core function of a network protocol. While ensuring data privacy and security may be aspects of certain protocols, it is not their defining characteristic. Similarly, a framework for mobile application design and guidelines for coding syntax pertain to software development rather than network communication.