In path monitoring, what is used to monitor remote network devices?

Ping (ICMP echo requests) is a standard and effective method used in path monitoring to determine the reachability and responsiveness of a remote device by sending packets and waiting for replies, which can then influence routing decisions.

SSL is a protocol for encrypting communication, typically used for secure data exchange, not a mechanism for simply monitoring basic device reachability.

HTTP is a protocol for web communication and is not typically used for basic network device reachability monitoring in a path monitoring context.

HTTPS is the secure version of HTTP and, like HTTP, is not primarily used for simple device reachability monitoring in this context.

Link State refers to routing protocols (e.g., OSPF) that share network topology information, but it is not a direct method used by the firewall to monitor the reachability of a specific remote device.