ICMP, Internet Control Message Protocol, is a set format that contains packets that show error, control, and informational messages. This format is an expansion of the IP, Internet Protocol, which is used to transfer packets or sets of data. ICMP is used by routers or other devices to report or acquire information. The ICMP protocol is setup by the RFC792 standard. This standard sets what each bit in the packet of the protocol means. RFC 1349 explains how ICMP is used in different IP types. According to RFC792, the ICMP header which is directly after the IP header changes depending on the ICMP type. The basic header shape looks like this: