Re: Support for 240/4 and 0/8 addresses in NetBSD

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Thu, 15 Jun 2023 15:20:22 -0400 (EDT)
    From:        Mouse <mouse%Rodents-Montreal.ORG@localhost>
    Message-ID:  <202306151920.PAA25034%Stone.Rodents-Montreal.ORG@localhost>

  | So, for as long as there have been classes and as long as localhost has
  | been 127.x.x.x (I don't know which happened first),

Classes came first, those date back to when IP addresses were expanded
from 8 to 32 bits (ie: long long ago).   localhost is also very old, it
predates any mention of anything related in any RFC - but it isn't quite
that old (further, using 127.0.0.1  means classes existed, as that's a 32
bit addr, and they existed from when 32 bit addrs were created)   Jon Postel's
assignment strategy can be seen throughout all of this (but not for localhost).
Class A was half the addr space, class B was half of what was left, class C
half of what was left after that ... the rest was initially held in reserve
(there was no concept of either broadcast or multicast originally).

localhost (as net 127) was "invented" (and in the code) long before subnets,
or any need for anything related to netmasks ever appeared.   While ethernet
(the original 3Mbps version) probably existed about the same time, it was
still very experimental, and expensive.   Almost no-one had LANs.

Localhost using net 127 was definitely picked as being the last class A
network number available (and hence one which was assumed at the time would
never actually be needed for anything - and in a way that's right, if the
preceding 126 were all used up, having one more available wasn't really
going to help anything much).

kre