An ICMP (Internet Control Message Protocol) packet does not have source and destination port numbers because it is not a transport layer protocol like TCP or UDP, which use port numbers to identify specific processes or applications on end systems. Instead, ICMP operates at a lower network layer, directly on top of IP, and is used for network management, diagnostics, and error reporting rather than data transfer between processes. Therefore, ICMP packets are identified by their type and code fields, which describe the kind of message being sent, and they communicate information between network devices such as routers and hosts, not between application processes. Because ICMP messages are interpreted by the network software itself rather than specific applications, port numbers are unnecessary and do not exist in ICMP packets.
