On Dec 19, 2018, at 3:50 AM, Brian Kantor <Brian@ampr.org> wrote:
/24 is certainly cleaner than 255.255.255.0.
I seem to remember it was Phil Karn who in the early 80's suggested that expressing subnet masks as the number of bits from the top end of the address word was efficient, since subnet masks were always a series of ones followd by zeros with no interspersing, which was incorporated (or independently invented) about a decade later as CIDR a.b.c.d/n notation in RFC1519. - Brian
Actually, not really. In the time frame, there was quite a bit of discussion about "discontiguous" subnet masks, which were masks that had at least one zero somewhere within the field of ones. There were some who thought they were pretty important. I don't recall whether it was Phil that suggested what we now call "prefixes" with a "prefix length", but it was not fait accompli. Going with prefixes as we now describe them certainly simplified a lot of things. Take a glance at https://www.google.com/search?q=discontiguous+subnet+masks for a history discussion.