[ih] The netmask

[Karl Auerbach]

As folks discuss this, let's not forget that interwoven with the 
subnet-mask and CIDR ideas was the question whether such masks had to be 
contiguous bits.

(I'm rather glad that we went with contiguous bits - otherwise would 
have perhaps led to a lot of chaos.)

(I remember at a San Diego IETF when Tony Li first informed me of CIDR 
ideas.)

	--karl--

On 1/7/25 5:47 AM, 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.