On Jan 3, 2008 3:52 AM, Rick Astley <jnanog@gmail.com> wrote:

>Take someone like Comcast with ~12 million subscribers.

>It would take an IPv6 /24 to get 16.7 million /48's (2^24). With a net efficiency of 10% they are going to need to be allocated 120 million /48's. It would take a /21 to give them 2^(48-21) = ~134 million /48's.

>So in short, a /48 to subscribers seems like complete overkill, and a /32 to ISP's seems completely inadequate (80 vs 16 bits).

>I thought one of the goals of IPv6 was to assign ISP's huge blocks with low utilization so they don't have push a bunch of individual prefixes out to the worlds routing tables?

>It seems to me while being extra super sure we meet goal 1 of making sure NAT is gone for ever (and ever) we fail goal 2 of not allocating a bunch of prefixes to ISP's that are too small.

PS. say for example we would like to meet goal 2 while giving customers /48's at the same time. We decide a an initial projected utilization of 1% or .1% is more appropriate for Comcast.

In order to give them 1.2 billion /48's (1% utilization), they would need 2 /18's.

For 12 billion (0.1% utilization), they would need a /14.
In which case the depletion of IPv6 space starts to seem possible.

Your response might be "Why would an ISP need 0.1% utilization?"
My answer: "Why would a customer need 0.000000000000000000000001% utilization?"