Understanding Guide to ICMP Protocol with Wireshark
From Wikipedia
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 which indicates that a requested service is not available or that a host or router could not be reached.
It is layer 3 i.e. network layer protocol used by the ping command for sending message through ICMP payload which is encapsulated with IP Header packet. According to MTU the size of ICMP packet cannot be greater than 1500 bytes.
ICMP packet at Network layer
IP headerICMP headerICMP payload size MTU (1500)20 bytes8 bytes1472 bytes (maximum)20 + 8 + 1472 = 1500
Full Article Read Here