Which statement is true regarding an NTRE in an External Time Reference Network (ETRN)?

In the context of an External Time Reference Network (ETRN), an NTRE (Network Time Reference Element) plays a critical role in establishing the overall timing framework necessary for operations. The statement that it is required to establish an ETRN is accurate because the NTRE is essential for ensuring all participants in the network are synchronized and can operate effectively. The NTRE helps provide a consistent reference time that various systems and devices within the network rely on to maintain timing accuracy.

This synchronization is vital in joint military operations where precision timing is essential for coordinating actions, managing communications, and ensuring the effective operation of Link-16 systems. Establishing an ETRN involves integrating various elements, including the NTRE, to ensure that all components can effectively communicate and respond in a unified manner. Therefore, the necessity of the NTRE in establishing an ETRN underscores its importance in maintaining the integrity and coordination of the network.