An Internet Standard protocol that is used to report error conditions during IP datagram processing and to exchange other information concerning the state of the IP network.
The Internet Control Message Protocol (ICMP) is a supporting protocol in the Internet protocol suite. It is used by network devices, including routers, to send error messages and operational information indicating success or failure when communicating with another IP address, for example, an error is indicated when a requested service is not available or that a host or router could not be reached. ICMP differs from transport protocols such as TCP and UDP in that it is not typically used to exchange data between systems, nor is it regularly employed by end-user network applications (with the exception of some diagnostic tools like ping and traceroute).
| Communication protocol | |
 A general header for ICMPv4 | |
| Purpose | Auxiliary protocol for IPv4 |
|---|---|
| Developer(s) | DARPA |
| Introduction | 1981 |
| OSI layer | Network layer |
| RFC(s) | RFC 792 |
ICMP for IPv4 is defined in RFC 792. A separate ICMPv6, defined by RFC 4443, is used with IPv6.
