Protocol design is a research area that focuses on the development and implementation of communication protocols for data transmission between devices in a network. This includes designing protocols for various network layers, such as the physical, data link, network, transport, and application layers. The goal of protocol design is to establish standardized rules and procedures for transmitting data efficiently and reliably within a network, ensuring interoperability and seamless communication between devices. Researchers in this field often study different network architectures, protocol performance, security, and scalability to improve the efficiency and effectiveness of communication protocols.