.Dd June 4, 2017
.Dt ICMP 4
.Os
.Sh NAME
.Nm icmp
.Nd internet control message protocol
.Sh SYNOPSIS
.In sys/socket.h
.In netinet/in.h
.Sh DESCRIPTION
The Internet Control Message Protocol (ICMP) is a control and error reporting
layer for the Internet Protocol version 4
.Xr ip 4 .
ICMP is commonly used to diagnose network problems, such as the destination
being unreachable, network congestion, packets exceeding their time to live, and
so on.
.Sh SEE ALSO
.Xr inet 4 ,
.Xr ip 4 ,
.Xr ping 4 ,
.Xr kernel 7
.Sh STANDARDS
.Rs
.%A J. Postel (ed.)
.%D September 1981
.%R STD 5
.%R RFC 792
.%T Internet Control Message Protocol - DARPA Internet Program Protocol Specification
.%Q USC/Information Sciences Institute
.Re
.Sh BUGS
ICMP is not implemented yet, except automatically replying to the Echo Request
message (ping) and the existence of
.Xr ping 4
sockets for sending Echo Request messages and receiving Echo Reply messages.