Topic summary
ICMP
Extracted from the Wikipedia article Internet Control Message Protocol.
Technical details
ICMP uses the basic support of IP as if it were a higher-level protocol; however, ICMP is actually an integral part of IP. Although ICMP messages are contained within standard IP packets, they are usually processed as a special case, distinguished from normal IP processing. In many cases, it is necessary to inspect the contents of the ICMP message and deliver the appropriate error message to the application responsible for transmitting the IP packet that prompted the ICMP message to be sent.