Interview question: Function of ICMP protocol
ICMP (Internet Control Message Protocol) protocol is a sub-protocol in the Internet protocol suite, and its main function is to provide error handling and control information on the IP datagram network. It contains common network control messages, such as sender and receiver inconsistent, request timed out, destination unreachable, etc.
The main functions of the ICMP protocol include the following three aspects:
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Error message delivery:
ICMP can help diagnose errors in the communication process of computers or ports, and send error information to the sender. If a host tries to send data to another host that cannot be reached, a "destination unreachable" error message is sent back to the sending host, telling it that the data has entered an infinite loop or attempted to send data to the wrong address. -
Activity test:
through ICMP, you can test the connectivity of the target host, that is, check the connection status through the Ping command. Ping is based on ICMP to transmit data. Host A sends an ICMP ECHO_REQUEST message containing a timestamp to the host B server, and host B returns an ICMP ECHO_REPLY message after receiving it, so that host A can know the delay time between the two hosts and transfer rate information. -
Provide QoS service:
It is beneficial to understand the data transmission situation and network topology of the network. ICMP is often used in the communication between routers or switches to determine which paths should be followed for the routing of data packets.
To sum up, the ICMP protocol is a sub-protocol in the Internet protocol suite, which provides functions such as error handling and control information for network communication, and can be used for error message delivery, activity testing, and QoS services.