Re: classful routes redux
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
Please pardon the crossposting between ppml and nanog... Geoff Huston <gih@apnic.net> writes:
Why /48 rather than /47 or /49? - alignment to nibble boundaries to make DNS delegation easier.
It has recently come to my attention that we are in error when we expect "n[iy]bble" to have the same amount of popular awareness as "byte". In point of fact, my guess is that most people who are not programmers (or particularly assembly language programmers) have minimal or no exposure to the term. Particularly in public policy discussions, such people abound, and their engagement in the process is no less important than that of a protocol implementer. Future proposals involving a preference toward doing things with 4-bit alignment should take care to explain what precisely a "n[iy]bble" is and hexadecimal numbering, and why it matters. ---Rob
participants (2)
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Geoff Huston -
Robert E.Seastrom