Which Internet protocol is used to detect errors in network communications?

• A. ICMP
• B. IP
• C. TCP
• D. UDP

Answer: (A)

ICMP is the protocol designed to report problems and provide diagnostics for IP traffic. It carries small control messages that inform the sender about issues encountered while delivering packets, such as a route being unreachable, a packet taking too long (time exceeded), or a header problem. This error-reporting capability helps diagnose network problems without delivering the actual data payload. For example, when a router can’t forward a packet because the destination is unreachable, it may send back an ICMP destination-unreachable message. When a packet’s time-to-live expires in transit, ICMP can generate a time-exceeded message to alert the origin. You often see ICMP in action with tools like ping, which uses ICMP echo request and echo reply messages to test reachability and measure latency.

In contrast, IP provides addressing and routing but does not actively report on delivery errors. TCP handles reliability at the transport layer through sequencing, acknowledgments, and retransmissions, ensuring data integrity for a connection-oriented session. UDP offers a best-effort service with no built-in error recovery or reporting. So the protocol dedicated to detecting and reporting errors in network communications is ICMP.