Ping message and ICMP message header

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ping message

ICMP Message header

ICMP What kind of agreement ？

ICMP Which layer of agreement ？

ICMP Port number ？

ICMP Message type

ICMP Message format

ping message

Ping yes ICMP An important application of , It is mainly used to test the connectivity between two hosts .

Ping The principle is to send ICMP Echo Request message , The destination host will send Echo Answer message .Ping The number of successful round trips and the response rate of packets are estimated .

This opportunity sends ICMP Send back the request message (request)：

The remote host will send a reply message after receiving it (reply)：

  common ping Instructions , stay linux Under the operating system ,request and reply Of data Are all ：!”#$%&’()+,-./01234567.

stay windwos In the environment ,ping Of data Part of it is ：abcdefghijklmnopqrstuvwabcdefghi

ICMP Message header

ICMP What kind of agreement ？

“icmp yes Internet Control message protocol . It is TCP/IP A sub protocol of a protocol family , Used in IP host 、 Routing control messages between routers . Control message means that the network is not accessible 、 Whether the host can reach 、 Whether the route is available and so on .” Although these control messages do not transmit user data , But it plays an important role in the transmission of user data .

ICMP Which layer of agreement ？

ICMP It belongs to network layer protocol .ICMP yes “InternetControlMessageProtocol” Abbreviation . It is TCP/IP A sub protocol of the protocol family , Used in IP host 、 Routing control messages between routers . Control message means that the network is not accessible 、 Whether the host can reach 、 Whether the route is available and so on .”

ICMP Port number ？

ICMP It's the control protocol , You don't need a port number .

ICMP Message type

 ICMP There are mainly two types of messages ： One is error report message (1~127), The other is query message ( The value is greater than 128).

ICMP Message format

About ICMP Message points ：

( Refer to (16 Bar message ) 9-ICMP Message type _songly_ The blog of -CSDN Blog _icmp What are the message types )

1. For carrying ICMP Datagram of error message , No longer produce ICMP Error message .
   If the host A Sent a ICMP Send the data message to the host B, An error occurred when the data passed through one of the routers during transmission , Because the router has received a ICMP The data packet , So there won't be another ICMP Error message .

2. For segmented datagrams , If it's not the first slice , It doesn't produce ICMP Error message
   For hosts A Sent a piece of data , If the fragment data received by the routing device or host is not the first fragment data , Will not produce ICMP Error message .

3. For datagrams with multicast addresses , Do not produce ICMP Error message
   If one ip If the address is a broadcast address , Will not produce ICMP Error message .

4. For special addresses, such as （127.0.0.0 or 0.0.0.0） Datagram , Do not produce ICMP Error message