[ih] The netmask

[Vint Cerf]

the original design just used 8 bits for network ID and 24 bits for host ID.
When LANS proliferated we went to class A,B,C,D,E structure. When class B
became exhausted we went to CIDR concept.

v


On Tue, Jan 7, 2025 at 8:47 AM Michael Grant via Internet-history <
internet-history at elists.isoc.org> 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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> Internet-history at elists.isoc.org
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>


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