What protocol is ICMP?

ICMP is (Internet Control Message Protocol) Internet Control Message Protocol. It is a subprotocol of the TCP/IP protocol suite and is used to transmit control messages between IP hosts and routers. Control messages refer to messages about the network itself, such as network connectivity, whether the host is reachable, and whether routes are available. Although these control messages do not transmit user data, they play an important role in the transmission of user data.

#The ICMP protocol is a connectionless-oriented protocol used to transmit error reporting control information. It is a very important protocol and it is extremely important for network security.

It is a sub-protocol of the TCP/IP protocol suite and is a network layer protocol. It is mainly used to transfer control information between hosts and routers, including reporting errors, exchanging restricted control and status information, etc. When IP data cannot access the target or the IP router cannot forward data packets at the current transmission rate, ICMP messages will be automatically sent. The value of the protocol type field (Protocol 8bit) in the header of the IP frame structure of the ICMP message is =1.

ICMP provides consistent and easy-to-understand error reporting information. The sent error message is returned to the device that sent the original data, because only the sending device is the logical recipient of the error message. The sending device can then determine the type of error that occurred based on the ICMP message and determine how best to resend the failed packet. But the only function of ICMP is to report problems rather than correct errors. The task of correcting errors is completed by the sender.

We often use the ICMP protocol in the network. For example, we often use the Ping command (available in both Linux and Windows) to check whether the network is accessible. This "Ping" process is actually ICMP. The process of agreement work. There are other network commands such as the Tracert command that trace routes, which are also based on the ICMP protocol.

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