[ih] The netmask

[Enno Rey]

Hi,

you may find the answer in this post or one of the links referenced there:

https://insinuator.net/2019/08/a-brief-history-of-the-ipv4-address-space/

cheers, Enno


On Tue, Jan 07, 2025 at 01:47:25PM +0000, Michael Grant via Internet-history wrote:
> Before CIDR sub-netting there were fixed subnets: A, B, C, D, & E.  (and
> from memory D and E came later).  What was the rational for this being
> represented as an actual bit-mask which could have been represented as a
> number of bits like we do today?  I know that not many protocols send the
> mask over the wire, aside from perhaps routing protocols.  Did any early
> protocols use say just 5 or even just 2 bits to represent classes before
> things went to CIDR?  I never saw anything like ifconfig report "Class C",
> it was always represented as 255.255.255.0.
> 
> I realize it's more efficient from a computing point of view to deal with
> bit-masks.  But I'm curious, from a historic point of view, why it wasn't
> just a number of bits or even just a number representing the class (A, B,
> C)?  In the old days when every byte of memory was sacred, it seems like it
> would have been thought of as wasteful.
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-- 
Enno Rey

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