Maybe it's time to play the "site" card? (Or hasn't that been played many times already?) Do you put a lower bound on what you call a "site"? Is a home network connected via DSL a "site"?
Yes.
What about a small business (sub-10 employees, say) which also uses DSL a "site" worthy of assignment of an entire /48?
Yes.
I can easily imagine ISPs having more then 64K (for the americans who might have a problem with math, that's 2^(48-32) :-) DSL users, and with the "one size fits all" address assignment policy outlined above, the ISP would blow through it's entire /32 by handing out IPv6 addresses to 65536 customers.
Big ISPs already ask for and receive IPv6 allocations much bigger than a /32.
We should never make changes to this architecture without considerable thought and understanding of the reasons why these prefix lengths were chosen.
Which, briefly summarized, were...?
If only the IETF would produce a document that covers the whole story... My understanding is that a big part of the architecture was to allow networks to grow, at any level in the addressing hierarchy without requiring any changes to the hierarchy itself. That's why a site gets more addresses than they need and why many ISPs also get more addresses than they need. Of course, in the Americas, they have tempered this by dividing sites into homes and others. An ISP can assign /56s to home sites rather than /48, if they want to. Of course this complicates management systems and planning, so ARIN made this optional. If a site really is a home, then /56 still meets the goal of giving more subnetting ability than they could possibly need.
IPv6 is not the same as IPv4.
So I continue to see people say, but I've yet to see a justification for such broad sweeping statements which I can agree with justifies the statement. From my perspective it's *really* the same protocol done a second time with more bits, and the number of bits is *not* infinite.
There are many ways in which IPv6 differs from IPv4, not just the addressing hierarchy. And even though the number of bits is not infinite, it is really, really big. Almost unimaginably big. We can afford to waste IPv6 addresses because even if we do run out some day, our great-grandchildren will have enough generations of network operational experience to design a proper Internet Protocol. --Michael Dillon