[ih] The netmask

[Grant Taylor]

On 1/7/25 12:02 PM, Andrew G. Malis via Internet-history wrote:
> While the RFC refers to bit-masks, operationally people realized that 
> since CIDR bit-masks were always all ones from the left and all zeros 
> from the right, they could be equivalently represented by an integer 
> count of one bits, usually following a "/" character.

I don't know if CIDR itself codified (sub)netmasks being sequential ones 
or not.  But I do know that some older TCP/IP implementations would work 
with netmasks that were non-contiguous ones.

I remember some early discussions about being EXTREMELY creative with 
non-contiguous bit patterns in netmasks in the mid-to-late '90s.  In 
retrospect, I'm glad that we settled on the simpler convention of 
contiguous ones.



-- 
Grant. . . .
unix || die