Which of the following protocols would be used to verify connectivity between two remote devices at the HIGHEST level of the OSI model?

ICMP operates at Layer 3 (Network) of the OSI model and is used by tools like ping to test basic network reachability, not application-layer connectivity.

IPSec operates at Layer 3 (Network) as a suite of protocols for securing IP communications, not at the Application layer.

SCP operates at Layer 7 (Application) of the OSI model because it is an application-level file transfer protocol built on top of SSH. It requires a full end-to-end connection including all lower layers, making it the highest-layer protocol among the choices. Using SCP to transfer data implicitly verifies connectivity at every OSI layer below it as well.

TCP operates at Layer 4 (Transport) of the OSI model, providing reliable connection-oriented communication but not reaching the Application layer.