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Re: classful routes redux

  • From: Geoff Huston
  • Date: Wed Nov 02 23:56:46 2005

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.