- It is used to send error & control information between ip network devices.
- There are many diffident messages that can be shared, including the following:
2. Echo Reply: Replies to ICMP echo request.
3. Destination Unreachable: Informs the host that a datagram can't be delivered.
4. Source Quench: Informs the host to lower the rate at which it sends datagram because of congestion.
5. Redirect: Informs the host of a preferred rate.
6. Time Exceeded: Indicate that the TTL of IP datagram has expired.