You are mixing different versioning systems. ICMP is protocol 1 inside Internet Protocol, where TCP is protocol 6 and UDP is 17 [0]. Internet version (as it nam

You are mixing different versioning systems. ICMP is protocol 1 inside Internet Protocol, where TCP is protocol 6 and UDP is 17 [0]. Internet version (as it named in rfc790) is defined with four first bits, numbers 1-3 unassigned and 4 is our IPv4[1] Technically ICMP is layer 4 protocol, but defined as integral part of IP [2] [0] https://en.wikipedia.org/wiki/List_of_IP_protocol_numbers https://en.wikipedia.org/wiki/List_of_IP_protocol_numbers [1] https://tools.ietf.org/html/rfc790 https://tools.ietf.org/html/rfc790 [2] https://tools.ietf.org/html/rfc792 https://tools.ietf.org/html/rfc792