What is the Internet Control Message Protocol (ICMP)?
The Internet Control Message Protocol is an internet layer protocol used by network devices to communicate. The network diagnostic tools traceroute and ping both operate using ICMP. Commonly, ICMP echo-request and echo-reply messages are used to ping a network device for the purpose of diagnosing the health and connectivity of the device and the connection between the sender and the device. Network attacks using ICMP as a means of disruption include the ICMP Flood Attack and The Ping of Death attack.