This network diagram illustrates how ICMP (Internet Control Message Protocol) operates in communication between devices. It shows the ICMP message exchange process, where a client sends an Echo Request to a host through a router and the internet, and receives an Echo Reply in return, confirming connectivity. The diagram also highlights an error case, where sending a packet to an invalid address results in an ICMP Destination Unreachable message. At the bottom, it depicts ICMP as part of the network layer, alongside IP, ARP, and IGMP, emphasizing its crucial role in network troubleshooting and diagnostics, such as the ping command.
