Transmission Control Protocol/Internet Protocol (TCP/IP) is the acronym identifying a suite or stack of protocols developed by the U.S. Department of Defense in the 1970s to support the construction of worldwide internetworks. TCP/IP are the two best-known protocols in the suite.
The TCP/IP stack also includes the Internet Control Message Protocol (ICMP) that is designed to help an administrator manage and control the operation of a TCP/IP network. Every now and then a gateway device, such as a router, or possibly the destination host, will communicate with a source host to report an error in datagram processing. As a tool in the troubleshooting process, ICMP is used.
ICMP is sometimes called an umbrella protocol because it contains many sub-protocols and provides a wide variety of information about a network’s health and operational status. Unique ICMP messages are sent in several situations such as:
- when a datagram cannot reach its destination
- when the gateway does not have the buffering capacity to store and then forward a datagram
- when the gateway can redirect the host to send traffic through a more optimal route
