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What is ICMP?
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- Skip2 Networks
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Internet Control Message Protocol (ICMP)
ICMP, or Internet Control Message Protocol, is a core protocol of the Internet Protocol (IP) suite, primarily used by network devices to send error messages and operational information. While IP handles the delivery of data packets, ICMP provides feedback about issues that prevent IP packets from reaching their destination or that indicate the status of the network. It's often thought of as the "error reporting" and "diagnostic" mechanism for the internet.
A common application of ICMP is the ping command, which sends ICMP "echo request" messages to a target host and listens for "echo reply" messages to determine connectivity and round-trip time. Similarly, traceroute uses ICMP to map the path a packet takes across a network. While crucial for network diagnostics and management, ICMP is also sometimes exploited in denial-of-service (DoS) attacks, such as "ICMP flood" attacks, where an overwhelming number of ICMP requests are sent to a target to consume its resources. For this reason, network administrators often configure firewalls to control or limit ICMP traffic.