Which of the following protocols does not apply to EtherNet/IP?

EtherNet/IP is built on standard Ethernet and utilizes two key layers for communication: the TCP/IP stack and the Common Industrial Protocol (CIP). The correct answer here is based on understanding the protocols that EtherNet/IP employs.

CIP is an important protocol that EtherNet/IP operates with to facilitate communication among devices in an industrial automation context. It defines the data and services used for device interoperability. Both TCP and UDP are equally relevant, as EtherNet/IP can utilize TCP for connection-oriented communication and UDP for connectionless communication, depending on the type of data being transmitted and the requirements for speed and reliability.

ICMP, on the other hand, is a network-layer protocol commonly used for error messaging and diagnostics in IP networks, such as to report issues like unreachable hosts. While ICMP is part of the Internet Protocol suite, it does not directly apply to the operational aspects or the service delivery of EtherNet/IP. Thus, it is correct that ICMP does not play a role in the functioning of EtherNet/IP, setting it apart from the other protocols listed.