lloyd.wood@xxxxxxxxxxx wrote: >> Are you saying that some datalink protocol relies on IP version >> field to demultiplex IPv4 and IPv6, even though the protocol >> must have some field to demultiplex IP and non-IP? >> >> For example? > ISO HDLC. What do you mean "ISO HDLC"? Where is a specification of "IP over ISO HDLC"? Masataka Ohta PS You should learn to quote properly.