Jonathon, On Aug 7, 2011, at 12:09 PM, Jonathon Exley wrote: > This has probably been said before,
Once or twice :-) > but it makes me uncomfortable to think of everybody in the world being given > /48 subnets by default. This isn't where the worry should be. Do the math. Right now, we're allocating something like 300,000,000 IPv4 addresses per year with a reasonable (handwave) percentage being used as NAT endpoints. If you cross your eyes sufficiently, that can look a bit like 300,000,000 networks being added per year. Translate that to IPv6 and /48s: There are 35,184,372,088,832 /48s in the format specifier currently defined for "global unicast". For the sake of argument, let's increase the the 'network addition' rate by 3 orders of magnitude to 300,000,000,000 per year. At that rate, which is equivalent to allocating 42 /48s per person on the planet per year, the current format specifier will last about 100 years. And there are 7 more format specifiers. > but wouldn't it be wise to apply some conservatism now to allow the IPv6 > address space to last for many more years? The area to be more conservative is, perhaps unsurprisingly, in the network bureaucratic layer. I believe current allocation policy states an ISP gets a minimum of a /32 (allowing them to assign 65536 /48s), but "if justified" an ISP can get more. There have been allocations of all sorts of shorter prefixes, e.g., /19s, /18s, and even (much) shorter. An ISP that has received a /19 has the ability to allocate half a billion /48s. And of course, there are the same number of /19s, /18s, and even (much) shorter prefixes in IPv6 as there are in IPv4... > After all, there are only 4 bits of IP version field so the basic packet > format won't last forever. True. There is no finite resource poor policy making can't make scarce. Regards, -drc
