Internet Control Message Protocol (ICMP)
Internet Control Message Protocol (ICMP) is used to communicate specific information between hosts about network or communications problems. Ping was designed to use ICMP in a heterogenous local area network environment to determine the round trip time and availability of a remote host. Ping was never intended for use in the general Internet, but it is the most comonly used network troubleshooting tool available.
ICMP is implemented as part of IP, but runs as if it were a higher level protocol (it's encapsulated within IP).
ICMP MESSAGE TYPES
- Echo / Reply
- Destination Unreachable
- Source Quench
- Redirect
- Time Exceeded
- Parameter Problem
- Timestamp / Reply
- Information Request / Reply
PING - AN ICMP APPLICATION
ICMP STANDARDS DOCUMENTATION
- RFC 792 - Internet Control Message Protocol
unreachable >>