Just a example for Tibby, why it is a issue, when your all devices are connected directly to the internet without NAT - with extra octet, country like USA would be limited to 4294967296/311478119=13.78 devices per person. Sounds ok-ish, if you have just few computers, starts to be problematic when you start to have more (TV, radio, fridge,...). Now let's look at China - 4294967296/1339724852=3.2. Whoops, only 3 devices per person in China. Oh well, let's add China more blocks, to have it equal with USA we need to give them 4 blocks. 253 (because you can't use the 0 or 255) minus 224 (number of countries in the world) brings us to 29 reserve blocks. So, we need to give 3 extra blocks to China, 3 to India. That brings us down to 23 reserve blocks - if we take the 13 devices per country as a basis. But why not take something more close to the average as a basis, for example Russia with population of 142,905,200 - that is 30 IP per person. To get that, you need to give 9 extra blocks to China, 9 to India, 2 to USA and 1 to Indonesia, Brazil, Pakistan,Nigeria and Bangladesh. Whoops, we are left with just 3 spare blocks, and we are still limited to 30 IP per person (in the larger countries; in small ones like Slovakia we would have 858 IP per person). With IPv6, we get 4.91567039 × 10^28 IP adresses per person. Enough said .