ICMP is an extension to the Internet Protocol. It allows for the generation of error messages, test packets and informational messages related to IP. It is defined in STD 5, RFC 792. [Source: FYI4]
INTERNET CONTROL MESSAGE PROTOCOL
Meaning of INTERNET CONTROL MESSAGE PROTOCOL in English
Internetworking Terms English vocab. Английский словарь межсетевых терминов. 2012