Which statement correctly describes ICMP echo messages?

• A. They are used for error reporting only.
• B. They are used to carry large payloads.
• C. They are used for reachability checks, commonly known as ping.
• D. They are used primarily for data transfer.

Answer: (C)

ICMP echo messages exist to check reachability and measure round-trip time, which is exactly what the ping utility uses. When a host sends an Echo Request, a reachable destination responds with an Echo Reply, allowing the sender to confirm the path is working and to gauge latency. They’re not error reports and aren’t intended for moving large amounts of data; their payload is small and primarily for identification and timing, not bulk transfer. Some networks may block ICMP echoes for security, but the fundamental purpose remains diagnosing reachability and latency.