But I still think that it needs to be pointed out that the standard prefix lengths of /64 for a subnet, /48 for a site, and /32 for an ISP, provide real benefits in network architecture and design.
The /64 for subnet I can understand, as automatic address assignment relies on it. However, I think I personally would be more cautious in using such big words about the /48 and /32 limits. Sure, they're fine round binary numbers, but are they *really* anything more than that? 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"? What about a small business (sub-10 employees, say) which also uses DSL a "site" worthy of assignment of an entire /48? 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.
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...?
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. Regards, - Håvard