"When IP is using UDP/TCP to send packet, how about ICMP ? (ICMP's not using port)"

IP does not use UDP or TCP, but UDP and TCP use IP. In this sense, ICMP is just another TCP or UDP. This is about right, in the sense of their dependency on IP, but ICMP can also be think as a part of IP, and almost all IP implementation implements ICMP. Port is nothing but an identifier. IP address is the identifier used by IP, and UDP and TCP both added one level of addressing - the ports. ICMP uses the identifier that IP provides - the IP address.

"Where's the position of ICMP in TCP/IP layer?"

I assume that we are talking about the OSI layers. There is no TCP/IP layer, and they simply do not belong to the same layer. The IP is at the network layer, and TCP at the transport layer. Where is ICMP? Network layer, but not really at the same level as IP, actually as part of IP.

In reply to Re: Questions about socket raw, stream and socket programming by pg
in thread Questions about socket raw, stream and socket programming by doctor_moron

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