Stupid Question maybe?

Wed Dec 19 01:38:14 UTC 2018

On Dec 19, 2018, at 3:50 AM, Brian Kantor <Brian at 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.
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