Internet Control Message Protocol (ICMP)

The Internet Control Message Protocol (ICMP) is a fundamental part of the internet that helps devices communicate network issues. When a computer or server encounters problems—such as a destination being unreachable or a packet taking too long—ICMP sends messages to inform the sender about the issue. It also assists in diagnosing network problems, like using the "ping" command to see if another device is reachable. Essentially, ICMP acts as a feedback system, ensuring that network devices can share information about connectivity and troubleshoot issues efficiently.