On Tue, Nov 16, 2010 at 06:13:56PM +0100, Johann Borck wrote: >> I beg to differ. Dust mote sensor networks can easily be in >> excess of billions or trillions devices. >> >> > Hi, > I followed your discussion and thought above numbers justify a small > thought-experiment. I'm not a physician, but you're a chemist, and will > therefore be able to correct the mistakes I'll make in the following: > According to Wikipedia, world energy consumption in 2008 was 474 Total solar output flux is ~4 MT/s, Earth intercepts 2 kg/s of that. We use about 10^-4 of those 2 kg/s, or about 0.1 g/s. > exajoules. Now take 2^56 nodes, and you have 0.001827 kWh or 1.827 Wh I presume we've dropped the /64 node limitation. Notice that at the *current* allocation practices we're only a factor of 10^6 to 10^9 bigger than the current IPv4 space. With your 10^16 you're already by a factor of 10^10 to 10^7 off. > or 6578 J energy per node per *year*, ~ 200 uJ/s , which is unlikely to Erasing one bit takes KTlog 2 of energy, unless the computation is reversible -- so there's no limit, though it can get a bit slow. Communication of course takes also at least a few photons, so it will be slightly above that. > be enough even for future dust mote sensor networks. In the real world, > with IPv6, the limiting factor isn't address space anymore, it's energy. > Or put in more drastic terms, long before we've run out of address > space, mankind will be starved or frozen to death, since we'd allocate > each and every Joule of "available" energy to some kind of computer > system. Of course, but that limit is 4 MT/s. And yes, it will be all used eventually. >> Moreover, the solar system is pretty big. Add self-replicating >> hardware, and suddenly 128 bits and 35 years don't appear >> that much. >> > Wow, assuming self replicating hardware, why not also assume self Such are not nearly as far-fetched as people seem to think: http://www.molecularassembler.com/KSRM.htm You might have heard of current rapid protoping systems a la RepRap. > replicating address space, just to put your mind at ease? ;) That's just the point, once you've locked in a standard you cannot change it. Consider the amount of pain the current IPv4 to IPv6 will entail, including uneasy co-existance of dual-stacked network, tunneled protocols, autoconfig breakage and other funnies. Admittedly, I think IPv6 will by that time will become obviously legacy. > regards, Johann -- Eugen* Leitl <a href="leitlhttp://leitl.org">leitl</a> http://leitl.org ______________________________________________________________ ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE