An extension to the Internet Protocol (IP) defined by RFC 792. ICMP supports packets containing error, control, and informational messages. The PING command, for example, uses ICMP to test an Internet connection.
Internet Control Message Protocol. A Layer 3 protocol that is used to notify errors, send control messages, and test whether a destination is reachable. ICMP is part of the TCP/IP protocol suite. Also see OSI model.
Internet Control Message Protocol. In the Internet, a protocol that provides a means for communicating computers (both routers and hosts) to exchange error and informational messages in an IP network.