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What is ICMP? This is the function and how it works

What is ICMP? This is the function and how it works

What is ICMP? This is the function and how it works


 Perhaps only a few Internet users have heard of ICMP, in fact most of them do not even know that it has anything to do with the Internet. Therefore let's find out what is ICMP and how does it work?


ICMP is actually a protocol, like IP, TCP and UDP, so it plays quite an important role in the proper functioning of our Internet connection. Keep on reading if you want to know what ICMP is and how it can help us maintain our connection at an optimal level.



What is ICMP?


Internet Control Message Protocol or commonly abbreviated as ICMP is a network protocol that is useful for solving various problems related to connectivity. This protocol is used by various network devices, such as routers, modems, servers, and others.


As mentioned above that ICMP is a protocol like TCP and UDP, but unlike the two, ICMP is not generally used to facilitate the exchange of data between systems. Also, it's not often used in end-user network applications, unless it's a diagnostic tool.


The original ICMP definition was sketched out by Jon Postel, who contributed greatly and time and time again to the development of the Internet, and the first ICMP standard was published in April 1981 in RFC 777. Obviously, the initial definition underwent many changes to reach the form we are familiar with. now. The stable form of the protocol was published 5 months later than its initial definition, in September 1981, in RFC 792, and was also written by Postel.


How Does ICMP Work?


In simple terms, ICMP is used for error reporting by determining whether data reaches its intended destination relatively quickly or not. In the basic scenario, two devices are connected via the Internet and exchange information via what we call data packets or datagrams. What ICMP does is generate errors and share them with the device that sent the original data if the packet never reaches its destination.


For example, if you send a data packet that is too large for the router to handle, the router will first drop the packet and then generate an error message telling the sending device that the packet never reached its intended destination.


However, that's what we call a passive skill because there's absolutely nothing you need to do to receive this error message (if necessary). ICMP also has a more active utility, which we can rely on to perform various network troubleshooting operations.


Unlike TCP and UDP, ICMP does not require a device to be connected to send messages. In a TCP connection, for example, the connected devices need to perform a multi-step handshake, after which data can be transferred.


With ICMP, no connection needs to be made, a message can simply be sent instead of a connection. In addition, ICMP messages do not require a port to route messages, compared to TCP and UDP, which both use a specific port to route information. ICMP not only doesn't require ports, but actually doesn't allow targeting of specific ports.


ICMP messages are carried by IP packets but not loaded by them. Instead, they support these packets, because they are only generated if their carrier (i.e. IP packets) never reach their destination. More often than not, the circumstances that allowed an ICMP packet to appear resulted from the data available in the IP header of the failed packet.


Because ICMP includes data from the IP headers of failed packets, network analysis tools can be used to determine exactly which IP packets failed to transmit. However, the IP header is not the only type of information ICMP packets carry.


The ICMP packet stores the IP header, followed by the ICMP header, and the first eight bytes of the payload.

* IP header – contains details about the IP version, source and destination IP addresses, number of packets sent, protocol used, packet length, time to live (TTL), sync data, and the ID number for a particular data packet.

* ICMP header – contains code that helps categorize errors, sub-codes that facilitate error identification by offering a description, and checksums.

* Transport Layer header – first eight bytes of payload (transferred over TCP or UDP).


ICMP function


ICMP is actually a fairly complex protocol. It is designed especially for devices working on the line connecting the sending device to the receiving device. In addition, ICMP has many functions besides simply reporting errors in packet transmission and unreachable hosts. Here are the main functions of ICMP:

* Allow the router to notify the source when the IP packet sent by the source cannot be sent.

* Allow source to find all available paths to destination device.

* Allow source to check if destination device is online and up.

* Allow administrators to test connectivity and debug connectivity related issues.


ICMP Control messages


ICMP offers feedback and information about errors, control messages and management queries. The first code field in an ICMP block can convey a lot of information. Below you can find some of the most relevant values the first column of code can have and what they mean:

* 0 – Echo Reply – used for ping purposes

* 3 – Unreachable Destinations

* 5 – Redirect Message – used to indicate a different route selection

* 8 – Echo Request – used for ping purposes

* 9 – Router Advertisement – used by routers to announce their IP address available for routing

* 10 – Router Solicitation – finding, requesting, or selecting a router

* 11 – Time Exceeded – The TTL expired or the reinstall time was exceeded

* 12 – Parameter Problem: Bad IP header – bad length, missing required options, or pointer error

* 13 – Timestamps

* 14 – Timestamp replies

* 41 – used for experimental mobility protocols

* 42 – Extended Echo Request – requests extended Echo

* 43 – Extended Echo Reply – replies to 42 extended Echo requests

* 253 and 254 – trials


Conclusion


So what is ICMP? The Internet Control Message Protocol (ICMP) is a protocol that devices on a network use to communicate problems with data transmission. The main function of ICMP is to report errors and perform network diagnostics.


ICMP works by conveying messages from the recipient to the sender about the data that should arrive. If data does not reach the recipient or is received in the wrong order, ICMP notifies the sender so that the data can be resent.

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So many articles What is ICMP. Look forward to other interesting articles and don't forget to share this article with your friends. Thank you…


Resa Risyan


Just an ordinary person who wants to share a little knowledge, hopefully the knowledge I provide can be useful for all of us. Keep in mind! Useful knowledge is an investment in the afterlife.


Also, read the article about What Is Imaglarger And How To Use It?. And see you in another article. Bye
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