4 ms·

> The one absolutely redeeming quality of IPv6 is that with 128 bits routing can be kept much more hierarchical and stateless. For now. Yes, 128 bits is a lot.

by thaeli 7y ago

> The one absolutely redeeming quality of IPv6 is that with 128 bits routing can be kept much more hierarchical and stateless. For now. Yes, 128 bits is a lot. Yes, even the 64 bit host-part is a lot. But the old-fashioned, pre-CIDR allocation strategy of IPv6 is _incredibly_ wasteful of address space. There are advantages, and for a single-planet, pre-IoT Internet, that's plenty. But IPv6 has taken so long to adopt, and future major stack changes will only be harder, that we really do need to think about what will work for the Internet a hundred years from now.

jandrese 7y ago
I don't think you realize just how big 64 bits for the network address is. It's one of those things where the scale is so large it's outside of normal human experience and we just can't hold it in our minds. There is no danger of running out of addresses for hundreds of years unless we decide it is necessary to give every single atom in the Earth its own /64. Even then we would have plenty of room to spare in the address space. It's just an absurdly large number. Giving out a few thousand to anybody who asks will never be a problem until humans have literally filled the galaxy.
- carapace 7y ago
  The example I've heard and like the best: With 64 bits you can address every cubic centimeter in the Solar system.
  - vardump 7y ago
    Earth's volume is 9.38e11 km^3. Or 9.38e23 liters (dm^3, cubic decimeters). 9.38 * 10^11 km^3 / (2^64) in m^3 = 50.8 m^3. So you'd have one 64-bit address for every 50.8 cubic meters of earth. Also, what's the volume of the solar system?
    - Dylan16807 7y ago
      Yeah that number is definitely wrong. The best fit I can find is that 128 bits is roughly enough to address every cubic meter in a sphere slightly larger than Neptune's orbit. 64 bits is way too big for a single dimension, but way too small for three dimensions.
      - nybble41 7y ago
        128 bits is enough to allocate 170 unique addresses to every milligram of matter in the Solar System (~99.9% of which is the Sun, about 2 * 10^33 grams). I think that's a more useful measure than the volume of the Solar System, which after all is mostly empty space. After all, what's the smallest (lightest) device which can benefit from having its own IPv6 address?
    - Dagger2 7y ago
      Based on the GP post, I believe the solar system is a sphere with radius 16.4 km. The volume would, therefore, be almost exactly 2^64 cubic centimeters.
    - zimpenfish 7y ago
      https://en.wikipedia.org/wiki/Solar_System https://en.wikipedia.org/wiki/Solar_System suggests 40AU is a reasonable radius (call it 6 billion km). Which gives a spherical volume of 9.05x10^38 m^3 giving you one address per 4.16x10^10 km^3. You could consider it a disc that just encapsulates the sun - then the volume is 1.57x10^35 m^3 and your address gets you a mere 8.5x10^6 km^3.
zAy0LfpBZLC8mAC 7y ago
> But the old-fashioned, pre-CIDR allocation strategy of IPv6 is _incredibly_ wasteful of address space. What would be wasteful would be keeping even more address space unallocated, as that would cause all kinds of costs, from administrative overhead, incentives to build unnecessarily suboptimal networks, delays due to address allocation processing, to more fragmented and thus larger routing tables and renumbering. Saving address space for the sake of saving address space is not useful.
- kortilla 7y ago
  But a 64 for a single host isn’t driven by any of that.
  - zAy0LfpBZLC8mAC 7y ago
    Who is suggesting that you use "64"(?) for a single host?
- login01 7y ago
  Funny, IPv6 is _incredibly_ wasteful of address space.... Only 1/8 of the address space is allocation using this strategy. Based on current projects, we won't need to break into the additional space till 2035 or later.
stordoff 7y ago
You could give every single IPv4 host its own complete IPv4 address space, and you would _still_ have enough addresses for 2 * 10^19 planets[1]. 2^128 is _absurdly_ large. [1] 2^128 / (2^32 * 2^32) = 1.84 * 10^19
Dylan16807 7y ago
> for a single-planet, pre-IoT Internet, that's plenty The main assignment blocks right now are some /12s. We can easily split off a /8 for every planet and moon, or whatever. Communication between stars won't work with IP, let's worry about that issue later. Internet of things isn't an issue at all here. You can cram as many as you want into a single subnet. If you desperately need an enormous pile of subnets for IoT for some reason, it's straightforward to take a /64 and chop it into a billion subnets that hold a billion devices each.

by thaeli 7y ago

jandrese 7y ago

I don't think you realize just how big 64 bits for the network address is. It's one of those things where the scale is so large it's outside of normal human experience and we just can't hold it in our minds. There is no danger of running out of addresses for hundreds of years unless we decide it is necessary to give every single atom in the Earth its own /64. Even then we would have plenty of room to spare in the address space. It's just an absurdly large number. Giving out a few thousand to anybody who asks will never be a problem until humans have literally filled the galaxy.

carapace 7y ago
The example I've heard and like the best: With 64 bits you can address every cubic centimeter in the Solar system.
- vardump 7y ago
  Earth's volume is 9.38e11 km^3. Or 9.38e23 liters (dm^3, cubic decimeters). 9.38 * 10^11 km^3 / (2^64) in m^3 = 50.8 m^3. So you'd have one 64-bit address for every 50.8 cubic meters of earth. Also, what's the volume of the solar system?
  - Dylan16807 7y ago
    Yeah that number is definitely wrong. The best fit I can find is that 128 bits is roughly enough to address every cubic meter in a sphere slightly larger than Neptune's orbit. 64 bits is way too big for a single dimension, but way too small for three dimensions.
    - nybble41 7y ago
      128 bits is enough to allocate 170 unique addresses to every milligram of matter in the Solar System (~99.9% of which is the Sun, about 2 * 10^33 grams). I think that's a more useful measure than the volume of the Solar System, which after all is mostly empty space. After all, what's the smallest (lightest) device which can benefit from having its own IPv6 address?
  - Dagger2 7y ago
    Based on the GP post, I believe the solar system is a sphere with radius 16.4 km. The volume would, therefore, be almost exactly 2^64 cubic centimeters.
  - zimpenfish 7y ago
    https://en.wikipedia.org/wiki/Solar_System https://en.wikipedia.org/wiki/Solar_System suggests 40AU is a reasonable radius (call it 6 billion km). Which gives a spherical volume of 9.05x10^38 m^3 giving you one address per 4.16x10^10 km^3. You could consider it a disc that just encapsulates the sun - then the volume is 1.57x10^35 m^3 and your address gets you a mere 8.5x10^6 km^3.

zAy0LfpBZLC8mAC 7y ago

> But the old-fashioned, pre-CIDR allocation strategy of IPv6 is _incredibly_ wasteful of address space. What would be wasteful would be keeping even more address space unallocated, as that would cause all kinds of costs, from administrative overhead, incentives to build unnecessarily suboptimal networks, delays due to address allocation processing, to more fragmented and thus larger routing tables and renumbering. Saving address space for the sake of saving address space is not useful.

kortilla 7y ago
But a 64 for a single host isn’t driven by any of that.
- zAy0LfpBZLC8mAC 7y ago
  Who is suggesting that you use "64"(?) for a single host?
login01 7y ago
Funny, IPv6 is _incredibly_ wasteful of address space.... Only 1/8 of the address space is allocation using this strategy. Based on current projects, we won't need to break into the additional space till 2035 or later.

stordoff 7y ago

You could give every single IPv4 host its own complete IPv4 address space, and you would _still_ have enough addresses for 2 * 10^19 planets[1]. 2^128 is _absurdly_ large. [1] 2^128 / (2^32 * 2^32) = 1.84 * 10^19

Dylan16807 7y ago

> for a single-planet, pre-IoT Internet, that's plenty The main assignment blocks right now are some /12s. We can easily split off a /8 for every planet and moon, or whatever. Communication between stars won't work with IP, let's worry about that issue later. Internet of things isn't an issue at all here. You can cram as many as you want into a single subnet. If you desperately need an enormous pile of subnets for IoT for some reason, it's straightforward to take a /64 and chop it into a billion subnets that hold a billion devices each.