A 260-bit address should be sufficient to address every atom in the universe, according to current estimates (10^78 atoms). We go there next (plus some extra to add hierarchy), and we'll never have to worry about addressing again. Another alternative is self-describing variable-length addresses, again do it once and we'll never have to worry about it again. Cheers, Andy On Thu, Aug 9, 2012 at 12:45 PM, Worley, Dale R (Dale) <dworley@xxxxxxxxx> wrote: >> From: Phillip Hallam-Baker [hallam@xxxxxxxxx] >> >> As Tom Knight pointed out when the IPv4 address size was chosen, there >> aren't enough for one for each person living on the planet. >> >> Remember that we are trying to build a network that is going to last >> for hundreds if not thousands of years. > > Technology changes over time, and so the optimal design tradeoffs > change over time. When IPv4 was designed, memory, processing power, > and transmission capacity were far more expensive than now. Moore's > Law suggests a factor of 2^15 between 1982 and 2012. Before that was > the ARPAnet, with 8 bit addresses, which lasted for around 15 years. > Presumably IPv6 will suffice for at least another 30 years. > > The real issue regarding longevity is that total network overhauls > should be infrequent enough that their amortized costs are well less > than ongoing operational costs. Once that has been achieved, the cost > savings of designing a protocol with a longer usable lifetime is > probably not worth the effort of trying to predict the future well > enough to achieve longer lifetime. > > Extrapolating a 30-year lifetime for each IP version suggests that in > 300 years we will reach the end of the usable life of IPv15 and will have > to allocate more bits to the "version" field at the beginning of > packets. That'll be a mess... > > Dale