ICMP (Part 3) – Concept Consolidation
Now let’s consolidate the concept of ICMP from what we discussed before. When a gateway on the Internet cannot pass the data packet to the next gateway, it will send a ICMP reply message (according to the error status) back to the sender computer. Consider the situation that shown in the diagram below:
More Concept of ICMP:
ICMP was designed as a way to send error and diagnostic messages in an IP inter-network.
- * ICMP messages are identified by “type” numbers.
- Each ICMP message also has a “code” number, which specifies a particular error code for that message type.
ICMP messages are carried inside IP packets. And ICMP should be considered as an integral part of IP, not as a higher-layer protocol.
Tomorrow I will discuss briefly how ICMP messages are sent back to sender computer in case a gateway on the Internet cannot pass the data packet to the next gateway.