Updated: 01/31/2019 by Computer Hope

Short for Internet Control Message Protocol, ICMP is an Internet Protocol extension defined by RFC 792 and an error reporting protocol for TCP/IP (transmission control protocol/Internet protocol) messages. Most users are familiar with ICMP from using the ping command.


With the different IP (Internet Protocol) versions, there are two ICMP versions, ICMPv4 for IPv4 and ICMPv6 for IPv6.

ICMP is used by computers and all types of network devices, including network routers, which help identify problems and communicate the status of devices on the network. The ICMP message contains a TYPE, CODE, and CHECKSUM message that help identify a device's response. The chart below shows a listing of the defined types and their descriptions.

ICMP TYPE ICMP Description
0 Echo reply.
3 Destination unreachable.
4 Source quench.
5 Redirect message.
8 Echo request.
11 Time exceeded.
12 Parameter problem.
13 Timestamp request.
14 Timestamp reply.
15 Information request (no longer used).
16 Information reply (no longer used).
17 Address mask request.
18 Address mask reply.

Computer acronyms, Network terms, Protocol, RFC, Traceroute