The Important Functions of ICMP (Internet Control Message Protocol)

ICMP (Internet Control Message Protocol) is a network layer protocol that generates error reports while facing problems with receiving or delivering packets.

It is a connectionless protocol with the primary duty of error reporting.

So, why is ICMP important?

Let us check why we need ICMP.

Checking the connectivity between two devices is the primary focus of network troubleshooting.

We have many utilities to check the connectivity and availability of the destination device.

All these utilities have their base on ICMP, defined in RFC 792.

ICMP works behind the Utilities like ping, tracert, etc. This tutorial explains the functions of Internet Control Message Protocol and the list of error messages generated by ICMP.

Now we will check the functions of Internet Control Message Protocol.

1. Send echo requests from a TCP/IP device to another
   
   
2. Responds to Echo request
   
   
3. It helps to find routing path issues.
   
   
4. ICMP echo message verifies the availability of the destination.

1. Address Request
   
   
2. Address reply
   
   
3. Destination unreachable
   
   To learn more about the Destination unreachable message generated by Internet Control Message Protocol, visit the links below.
   
   
   • Destination Net Unreachable
     
     
   • Destination Host Unreachable
     
   
   
4. Subnet Mask Request
   
   
5. Time Exceeded

You have learned about the Internet Control Message Protocol. Now is the time to check the practical use of it.

I have a home network with devices connected to the Internet through an ISP-provided modem.

I also have a small office with ten computers. I am sharing a hypothetical connectivity issue between my home computer and office network.

So, how should I start the troubleshooting if I cannot access the office network from home?

I will ping the office device from my personal computer at home.

It will send ping packets from my home computer to the office computer. Here we can see two functions of ICMP.

1. It tests the connectivity between my home computer and office computer.

2. It also generates an error report if there is a connectivity issue.

ICMP also helps troubleshoot connection issues between multiple hops.

We use the Tracert command for this purpose. Tracert also works basis on ICMP.