Re: classful routes redux

[Geoff Huston <gih () apnic net>]

At 01:16 PM 3/11/2005, Christopher L. Morrow wrote:


> On Wed, 2 Nov 2005, Fred Baker wrote:
>
> >
> > actually, no, I could compare a /48 to a class A.
> >
>
> (someone might already have asked this, but...) why /48?

Because the thinking at the time appears to be that to "ease' renumbering 
reduce the costs associated with address distribution functions (and 
associated network assessment tasks) and because there were heaps of 
addresses, all end-sites would get the same address allocation, and the 
uniform amount that was arrived at was a /48 . When asked whether this 
referred to _everything_ that may require subnets, the answer was "yes". 
When asked whether this encompassed everything from a mobile phone to a 
large corporate the  answer given was, once more, "yes".

Why /48 rather than /47 or /49? - alignment to nibble boundaries to make 
DNS delegation easier.

Why /48 rather than /32 or /40? I really cannot say - I suspect that /48 is 
the largest end site number that meets the projected scope as described in 
RFC 3177.


regards,

   Geoff