On Mon, 14 Dec 2015 04:10:34 +0000 (UTC) <lloyd.wood@xxxxxxxxxxx> wrote: > IP protocol version 5 is already defined and in usefor RFC1190, and > that use would have to be deprecatedfirst. Picking 7 is easier; for a > long time someoneon this list was pushing an idea of IPv8... and IPv9. I believe the IPv8 you are referring to was hardly a serious proposal. Regardless, 7, 8 and 9 were reserved for TP/IX, PIP and TUBA respectively. <https://www.iana.org/assignments/version-numbers/version-numbers.xhtml> John