If a Fax using V.34 communicates with one using V.17, what should happen?

When a fax machine using V.34 communicates with one using V.17, it is essential for the two machines to establish a common protocol they can both support to ensure successful communication. V.34 is a more advanced protocol that can operate at faster transmission speeds compared to V.17. However, since one of the machines is limited to V.17, the V.34 fax machine must drop back to the capabilities of the V.17 protocol.

This process, known as a fallback, enables the two devices to synchronize their communication parameters, allowing the V.34 machine to adapt to the V.17's limitations. As a result, the fax communication can proceed successfully even though it is at a slower speed. Emphasizing this adaptability in network protocols is critical for maintaining compatibility between different equipment, thus ensuring that fax transmission can occur regardless of the differences in technology between the two devices.

Options suggesting a failure in communication or that the V.34 would continue at its speed or upgrade to V.34 miss the point of interoperability and compatibility clearly defined in fax protocols.