[ih] The netmask

[Alejandro Acosta]

Hello all,

   I have been reading all the emails in this thread. So, I decided to 
try something "interesting".

   I have taken note of every RFC that have been mentioned in this 
discussion, I searched for the URLs. I also got every URL for the thread 
in the mailman; I added all these links to Google NotebookLM and it 
generated a quite interesting notebook (unfortunately I can not share it 
with everyone as google drive allows).

   Why am I saying this?. I'm thinking in publishing a blog post called 
something like: "the story behind the netmask" or something like that.

   I promise I will point to the mailing list and RFCs (if any of you 
want to join me in the blog post as author feel free to let me know)


Thanks,


Alejandro Acosta

R+D Coordinator at LACNIC



On 7/1/25 9:47 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.