6 ms·

> What am I missing? A few things. There's only 4,294,967,296 addresses in IPv4, so if you hand out giant blocks, you run out quite fast, whereas with 340,282

> What am I missing? A few things. There's only 4,294,967,296 addresses in IPv4, so if you hand out giant blocks, you run out quite fast, whereas with 340,282,366,920,938,463,463,374,607,431,768,211,456 you could hand out huge IPv4 /8 sized blocks from now until the heat death of the sun if you wanted to. But there's more to it than that. Right now only 1/8th of the IPv6 address space is "assigned to the internet", so there's effectively 7/8ths being held in reserve for the foreseable future -- this is partially to accommodate realistic router memory limits in the near term. IPv6 also has a more efficient hierarchical routing scheme than CIDR (which was kind of bolted on to IPv4 after-the-fact), which helps keep router tables from consuming terabytes of RAM. And IPv6 is designed to be more easily renumberable when we do make mistakes with assignments, with a clear separation between subnet prefix all that requires is changing the routing prefix. At the end of the day, with 340 trillion trillion trillion addresses, handing out too many isn't ever going to be a big worry in the foreseeable lifetime of...anything, really.

thaumasiotes 11y ago
> At the end of the day, with 340 trillion trillion trillion addresses, handing out too many isn't ever going to be a big worry in the foreseeable lifetime of...anything, really. Well, why can't I have them all?
- msbarnett 11y ago
  You'll have to settle for a measly trillion of them
  - metaphor 11y ago
    Certain DARPA-funded emerging technologies[1] will more than likely need just a wee bit more than "a measly trillion". Before spending some time in a wireless sensor net research lab as an undergrad, I had a difficult time imagining the scale of an application that could justify such a massive network address space...probably because I was too focused on trying to visualize what it might look like without considering the possibility that it would be invisible to the human eye. [1] http://www.eecs.berkeley.edu/~pister/SmartDust/SmartDustBAA97-43-Abstract.pdf http://www.eecs.berkeley.edu/~pister/SmartDust/SmartDustBAA9...
    - msbarnett 11y ago
      consider that there are something like 3.35 * 10^22 water molecules on earth there are 3.4 * 10^38 addresses in the IPv6 space we could individual address every water molecule on earth and still have an enormous amount of space left over so even if DARPA is planning on replacing the oceans with dust (and somehow managing to not exhaust a number of critical resources in this drive to make a truly staggering volume of dust), it's still not an issue
      - metaphor 11y ago
        My thought process isn't as terrestrially constrained...qualitatively science fiction by today's measure, to be frank. I was thinking more along the lines of an architecture adopted today which survives many millennia into the future that accounts for exponential human population growth on a galactic scale, isn't limited by the natural resources of this planet, where increment() will be the only pragmatic address assignment operation, meaningful archaeologic insight might be attained by discovering a microscopic 128-bit invariant, and so on.
        msbarnett 11y ago
        I mean, yes, IPv6 fails the improbable science-fiction wish-list test, for any number of reasons beyond address space path MTU discovery algorithms aren't going to be efficient when packet transit times are measured in decades, for one thing
vacri 11y ago
> There's only 4,294,967,296 addresses in IPv4 In an internet-usable sense, there's fewer than that, too. The entire 127.0.0.0/8 block is for localhost/loopback, for example. https://en.wikipedia.org/wiki/IPv4#Special-use_addresses https://en.wikipedia.org/wiki/IPv4#Special-use_addresses
- duskwuff 11y ago
  Worse: 224.0.0.0/4 and 240.0.0.0/4 are reserved, have always been reserved, and cannot in any practical terms be allocated, as there's huge amounts of hardware and software in production that's hard-coded to treat them as invalid. That's 1/8 of the entire IPv4 address space that's completely unusable.
  - simoncion 11y ago
    224.0.0.0/4 is IPv4 multicast space. It's not reserved and often in active use. [0] If there's software that treats IP traffic to or from 240.0.0.0/4 as invalid, then it's defective. I mean, I get that the broken software is a concern, but -if we care about carving out more IPv4 space- it's not something that we should be overly worried about. :) [0] Indeed, mDNS/Bonjour/Avahi uses 224.0.0.251 for service discovery.
    - duskwuff 11y ago
      Perhaps I should clarify: That range isn't general-purpose IP space. And while multicast is useful, there's probably ways to implement it without sacrificing 1/16 of the entire address space.
      - simoncion 11y ago
        > ...while multicast is useful, there's probably ways to implement it without sacrificing 1/16 of the entire address space. It's far too late for that now. :( Perhaps if IPv4 multicast were more widely used on The Internet the large carve-out would look more sensible to you. > That range isn't general-purpose IP space. Yeah, that's a true statement. Just remember that "reserved" has a particular meaning when it comes to IP address ranges. :)
wtbob 11y ago
> There's only 4,294,967,296 addresses in IPv4, so if you hand out giant blocks, you run out quite fast, whereas with 340,282,366,920,938,463,463,374,607,431,768,211,456 you could hand out huge IPv4 /8 sized blocks from now until the heat death of the sun if you wanted to. Well, according to [1] the sun will stay white-hot effectively forever. But, given that it will continue in its current state for another 5 billion years, and that there are 2^96 IPv4-sized blocks in IPv6's address space, one could give out 2.5e21 IPv4-sized blocks every second from now until the end of the sun's lifespan. So yeah, IPv6's address space is really, really, tremendously, amazingly, enormously big. [1] http://astrosociety.org/edu/publications/tnl/39/sun2.html http://astrosociety.org/edu/publications/tnl/39/sun2.html
- beefhash 11y ago
  This made me realize just how big a 128-bit key in cryptography really is.
  - ckozlowski 11y ago
    Indeed! It's bonkers. My college security professor once described a 128-bit key to us by imagining that every electron estimated to be in the known universe (think on this concept for a moment) had it's own unique value. For a 256-bit key, give each electron from above it's own universe, and assign values to all. That's the keyspace to be broken. Bruce Schneier once did a little thought exercise where he demonstrated that, assuming one needed to shift one electron (the absolute minimal amount needed to conceive of a compute switching operation), the energy requirements needed to brute force the key would exhaust the energy potential of the solar system. "These numbers have nothing to do with the technology of the devices; they are the maximums that thermodynamics will allow. And they strongly imply that brute-force attacks against 256-bit keys will be infeasible until computers are built from something other than matter and occupy something other than space." Interesting to ponder. (Source: https://www.schneier.com/blog/archives/2009/09/the_doghouse_cr.html https://www.schneier.com/blog/archives/2009/09/the_doghouse_... )
- msbarnett 11y ago
  I suppose the idiom is normally supposed to be "heat death of the universe", but yeah, either way, the IPv6 address space is just galactically, unfathomably huge
Sophira 11y ago
The fact that only 1/8th is assigned to "the Internet" right now is worrying. After all, we know how that worked out with the 240.0.0.0/4 range in IPv4 - it was reserved for future use, but was never able to be used because by the time it would have been useful, everything classed it as non-routable. It's a huge swath of addresses that just can't be used.
- dspillett 11y ago
  The only solution to that sort of thing is just to be bloody minded. Make it known from the start that when the currently unallocated blocks are needed they will be used, and if that breaks things for people who have used them already that is their fault and their problem to fix.
  - Sophira 11y ago
    To be clear, I don't mean that 240.0.0.0/4 isn't able to be globally routable because everybody's using it for their own private stuff. I mean that 240.0.0.0/4 isn't routable at all.
- msbarnett 11y ago
  Even if everything and everyone fails to learn the lesson of 240.0.0.0, and ignores the standard, and hard-codes the assumption that 7/8's of IPv6 is unusable forevermore, 1/8 of 340 trillion trillion trillion is still unfathomably huge
dfc 11y ago
> And IPv6 is designed to be more easily renumberable Can you point me to some information about this? I apologize if this is an easy question I am interested in ipv6 but only know enough to be confused more often than not.
joering2 11y ago
> At the end of the day, with 340 trillion trillion trillion addresses, handing out too many isn't ever going to be a big worry in the foreseeable lifetime of...anything, really. Gates already made that mistake. I know "this time is different", but if you start thinking of "internet of things", where literally every little thing in the world can be called (so needs its own name/number/ip/etc), then at some point we might run out of those numbers as well. I'm not sure how much (2^128) / 7 000 000 000 is, but it seemed not alot of every human's property can have its own address.
- ikeboy 11y ago
  Every human can have trillions of addresses and not use that up.
  - joering2 11y ago
    Then every "device" you have connected with every other person's device might need its own public address. And all of sudden, 640 kilobytes is not enough.
- kruczek 11y ago
  > I'm not sure how much (2^128) / 7 000 000 000 is, but it seemed not alot of every human's property can have its own address. Well, to put it into perspective, imagine that humans would colonize planets around all 400 billion stars in our galaxy (let's say that each star has 10 planets), with 7 billion people on each of them, and each person having 7 billion devices, each device could still have almost 2 million unique addresses available. The range by itself IS big enough for any foreseeable future. The problem may come from the fact that not all that range is available for use.
mrb 11y ago
"At the end of the day, with 340 trillion trillion trillion addresses, handing out too many isn't ever going to be a big worry in the foreseeable lifetime of...anything, really." This is untrue, and a big over exaggeration. Consider that pretty much any business (even a mom-and-pop shop) is allocated a /48 if they ask for it. Assuming one thousand /48 are allocated every second (ie. one thousand "business" IPv6 users coming online per second, which might be absolutely plausible 100+ years from now --we made IPv6 to be future proof right?), then we would run out of allocatable blocks in the global unicast IPv6 space (2000::/3) in 1,115 years. And we would run out of allocatable blocks in the entire IPv6 space in 8,919 years. So, yeah, I get annoyed when people mention the "death of the sun" or the "lifetime of the universe" when talking about IPv6, when in fact we could start running into exhaustion issues in the next ~1000 years. Note that I am being pedantic here. I think any technology that seems to scale "only" for our needs up to ~1000 years from now is good enough :)
- crxsec 11y ago
  By my calculations, you could assign 1000 /48 subnets per second for 4.8 trillion years before exhausting that space. http://www.wolframalpha.com/input/?i=%282%5E125%29%2F%282%5E48+*+1000+*+60+*+60+*+24+*+365%29+ http://www.wolframalpha.com/input/?i=%282%5E125%29%2F%282%5E...
  - mrb 11y ago
    You made an error. 2^48 should be replaced with 2^(128-48): http://www.wolframalpha.com/input/?i=%282%5E125%29%2F%282%5E%28128-48%29+*+1000+*+60+*+60+*+24+*+365%29+ http://www.wolframalpha.com/input/?i=%282%5E125%29%2F%282%5E...
    - crxsec 11y ago
      That seems.. correct. My bad!
aexaey 11y ago
The statement about IPv6 [internet] having 2^128 addresses is completely and utterly untrue, in the same way as it would be untrue to claim that IPv4 [internet] have 2^48 TCP ports. What IPv6 have address-space-wise, is 2^64 subnets, out of which 2^61 is actually allocated to be routable over public internet. Then comes granularity of /48 allocations (= 2^16 subnets) to end users and /32 allocations (= 2^32 subnets) to ISPs. That gives just 2^45 end users and 2^29 ISPs at best. In practice, if handing a user a /48 would become a common practice, all medium and large IPSs would start accumulating multiple /32s, then routing concerns would come back, and largest ISPs will start aggregating to /28s or /24s or whatnot. That is still a whole lot of addresses (and IPv4 still looks laughably small in comparison), but actual, practical numbers are way, way lower then "340 undecillion" marketing figure being plastered all over the place.
- km3k 11y ago
  From what I've read, most end users will get /56 blocks and larger organizations will be the ones to get a /48, so the potential end users is much higher than you've estimated.
  - aexaey 11y ago
    Blanket policy of /48 per end user comes from a (now obsolete) RFC3177. All RIRs now have less generous recommendations - both RIPE [0] and ARIN [1] seem to operate in /56 granularity nowadays, which is a very sensible step forward of course. [0] https://www.ripe.net/publications/docs/ripe-650 https://www.ripe.net/publications/docs/ripe-650 [1] https://www.arin.net/policy/nrpm.html#six7 https://www.arin.net/policy/nrpm.html#six7

thaumasiotes 11y ago

> At the end of the day, with 340 trillion trillion trillion addresses, handing out too many isn't ever going to be a big worry in the foreseeable lifetime of...anything, really. Well, why can't I have them all?

msbarnett 11y ago
You'll have to settle for a measly trillion of them
- metaphor 11y ago
  Certain DARPA-funded emerging technologies[1] will more than likely need just a wee bit more than "a measly trillion". Before spending some time in a wireless sensor net research lab as an undergrad, I had a difficult time imagining the scale of an application that could justify such a massive network address space...probably because I was too focused on trying to visualize what it might look like without considering the possibility that it would be invisible to the human eye. [1] http://www.eecs.berkeley.edu/~pister/SmartDust/SmartDustBAA97-43-Abstract.pdf http://www.eecs.berkeley.edu/~pister/SmartDust/SmartDustBAA9...
  - msbarnett 11y ago
    consider that there are something like 3.35 * 10^22 water molecules on earth there are 3.4 * 10^38 addresses in the IPv6 space we could individual address every water molecule on earth and still have an enormous amount of space left over so even if DARPA is planning on replacing the oceans with dust (and somehow managing to not exhaust a number of critical resources in this drive to make a truly staggering volume of dust), it's still not an issue
    - metaphor 11y ago
      My thought process isn't as terrestrially constrained...qualitatively science fiction by today's measure, to be frank. I was thinking more along the lines of an architecture adopted today which survives many millennia into the future that accounts for exponential human population growth on a galactic scale, isn't limited by the natural resources of this planet, where increment() will be the only pragmatic address assignment operation, meaningful archaeologic insight might be attained by discovering a microscopic 128-bit invariant, and so on.
      - msbarnett 11y ago
        I mean, yes, IPv6 fails the improbable science-fiction wish-list test, for any number of reasons beyond address space path MTU discovery algorithms aren't going to be efficient when packet transit times are measured in decades, for one thing

vacri 11y ago

> There's only 4,294,967,296 addresses in IPv4 In an internet-usable sense, there's fewer than that, too. The entire 127.0.0.0/8 block is for localhost/loopback, for example. https://en.wikipedia.org/wiki/IPv4#Special-use_addresses https://en.wikipedia.org/wiki/IPv4#Special-use_addresses

duskwuff 11y ago
Worse: 224.0.0.0/4 and 240.0.0.0/4 are reserved, have always been reserved, and cannot in any practical terms be allocated, as there's huge amounts of hardware and software in production that's hard-coded to treat them as invalid. That's 1/8 of the entire IPv4 address space that's completely unusable.
- simoncion 11y ago
  224.0.0.0/4 is IPv4 multicast space. It's not reserved and often in active use. [0] If there's software that treats IP traffic to or from 240.0.0.0/4 as invalid, then it's defective. I mean, I get that the broken software is a concern, but -if we care about carving out more IPv4 space- it's not something that we should be overly worried about. :) [0] Indeed, mDNS/Bonjour/Avahi uses 224.0.0.251 for service discovery.
  - duskwuff 11y ago
    Perhaps I should clarify: That range isn't general-purpose IP space. And while multicast is useful, there's probably ways to implement it without sacrificing 1/16 of the entire address space.
    - simoncion 11y ago
      > ...while multicast is useful, there's probably ways to implement it without sacrificing 1/16 of the entire address space. It's far too late for that now. :( Perhaps if IPv4 multicast were more widely used on The Internet the large carve-out would look more sensible to you. > That range isn't general-purpose IP space. Yeah, that's a true statement. Just remember that "reserved" has a particular meaning when it comes to IP address ranges. :)

wtbob 11y ago

> There's only 4,294,967,296 addresses in IPv4, so if you hand out giant blocks, you run out quite fast, whereas with 340,282,366,920,938,463,463,374,607,431,768,211,456 you could hand out huge IPv4 /8 sized blocks from now until the heat death of the sun if you wanted to. Well, according to [1] the sun will stay white-hot effectively forever. But, given that it will continue in its current state for another 5 billion years, and that there are 2^96 IPv4-sized blocks in IPv6's address space, one could give out 2.5e21 IPv4-sized blocks every second from now until the end of the sun's lifespan. So yeah, IPv6's address space is really, really, tremendously, amazingly, enormously big. [1] http://astrosociety.org/edu/publications/tnl/39/sun2.html http://astrosociety.org/edu/publications/tnl/39/sun2.html

beefhash 11y ago
This made me realize just how big a 128-bit key in cryptography really is.
- ckozlowski 11y ago
  Indeed! It's bonkers. My college security professor once described a 128-bit key to us by imagining that every electron estimated to be in the known universe (think on this concept for a moment) had it's own unique value. For a 256-bit key, give each electron from above it's own universe, and assign values to all. That's the keyspace to be broken. Bruce Schneier once did a little thought exercise where he demonstrated that, assuming one needed to shift one electron (the absolute minimal amount needed to conceive of a compute switching operation), the energy requirements needed to brute force the key would exhaust the energy potential of the solar system. "These numbers have nothing to do with the technology of the devices; they are the maximums that thermodynamics will allow. And they strongly imply that brute-force attacks against 256-bit keys will be infeasible until computers are built from something other than matter and occupy something other than space." Interesting to ponder. (Source: https://www.schneier.com/blog/archives/2009/09/the_doghouse_cr.html https://www.schneier.com/blog/archives/2009/09/the_doghouse_... )
msbarnett 11y ago
I suppose the idiom is normally supposed to be "heat death of the universe", but yeah, either way, the IPv6 address space is just galactically, unfathomably huge

Sophira 11y ago

The fact that only 1/8th is assigned to "the Internet" right now is worrying. After all, we know how that worked out with the 240.0.0.0/4 range in IPv4 - it was reserved for future use, but was never able to be used because by the time it would have been useful, everything classed it as non-routable. It's a huge swath of addresses that just can't be used.

dspillett 11y ago
The only solution to that sort of thing is just to be bloody minded. Make it known from the start that when the currently unallocated blocks are needed they will be used, and if that breaks things for people who have used them already that is their fault and their problem to fix.
- Sophira 11y ago
  To be clear, I don't mean that 240.0.0.0/4 isn't able to be globally routable because everybody's using it for their own private stuff. I mean that 240.0.0.0/4 isn't routable at all.
msbarnett 11y ago
Even if everything and everyone fails to learn the lesson of 240.0.0.0, and ignores the standard, and hard-codes the assumption that 7/8's of IPv6 is unusable forevermore, 1/8 of 340 trillion trillion trillion is still unfathomably huge

dfc 11y ago

> And IPv6 is designed to be more easily renumberable Can you point me to some information about this? I apologize if this is an easy question I am interested in ipv6 but only know enough to be confused more often than not.

joering2 11y ago

> At the end of the day, with 340 trillion trillion trillion addresses, handing out too many isn't ever going to be a big worry in the foreseeable lifetime of...anything, really. Gates already made that mistake. I know "this time is different", but if you start thinking of "internet of things", where literally every little thing in the world can be called (so needs its own name/number/ip/etc), then at some point we might run out of those numbers as well. I'm not sure how much (2^128) / 7 000 000 000 is, but it seemed not alot of every human's property can have its own address.

ikeboy 11y ago
Every human can have trillions of addresses and not use that up.
- joering2 11y ago
  Then every "device" you have connected with every other person's device might need its own public address. And all of sudden, 640 kilobytes is not enough.
kruczek 11y ago
> I'm not sure how much (2^128) / 7 000 000 000 is, but it seemed not alot of every human's property can have its own address. Well, to put it into perspective, imagine that humans would colonize planets around all 400 billion stars in our galaxy (let's say that each star has 10 planets), with 7 billion people on each of them, and each person having 7 billion devices, each device could still have almost 2 million unique addresses available. The range by itself IS big enough for any foreseeable future. The problem may come from the fact that not all that range is available for use.

mrb 11y ago

"At the end of the day, with 340 trillion trillion trillion addresses, handing out too many isn't ever going to be a big worry in the foreseeable lifetime of...anything, really." This is untrue, and a big over exaggeration. Consider that pretty much any business (even a mom-and-pop shop) is allocated a /48 if they ask for it. Assuming one thousand /48 are allocated every second (ie. one thousand "business" IPv6 users coming online per second, which might be absolutely plausible 100+ years from now --we made IPv6 to be future proof right?), then we would run out of allocatable blocks in the global unicast IPv6 space (2000::/3) in 1,115 years. And we would run out of allocatable blocks in the entire IPv6 space in 8,919 years. So, yeah, I get annoyed when people mention the "death of the sun" or the "lifetime of the universe" when talking about IPv6, when in fact we could start running into exhaustion issues in the next ~1000 years. Note that I am being pedantic here. I think any technology that seems to scale "only" for our needs up to ~1000 years from now is good enough :)

crxsec 11y ago
By my calculations, you could assign 1000 /48 subnets per second for 4.8 trillion years before exhausting that space. http://www.wolframalpha.com/input/?i=%282%5E125%29%2F%282%5E48+*+1000+*+60+*+60+*+24+*+365%29+ http://www.wolframalpha.com/input/?i=%282%5E125%29%2F%282%5E...
- mrb 11y ago
  You made an error. 2^48 should be replaced with 2^(128-48): http://www.wolframalpha.com/input/?i=%282%5E125%29%2F%282%5E%28128-48%29+*+1000+*+60+*+60+*+24+*+365%29+ http://www.wolframalpha.com/input/?i=%282%5E125%29%2F%282%5E...
  - crxsec 11y ago
    That seems.. correct. My bad!

aexaey 11y ago

The statement about IPv6 [internet] having 2^128 addresses is completely and utterly untrue, in the same way as it would be untrue to claim that IPv4 [internet] have 2^48 TCP ports. What IPv6 have address-space-wise, is 2^64 subnets, out of which 2^61 is actually allocated to be routable over public internet. Then comes granularity of /48 allocations (= 2^16 subnets) to end users and /32 allocations (= 2^32 subnets) to ISPs. That gives just 2^45 end users and 2^29 ISPs at best. In practice, if handing a user a /48 would become a common practice, all medium and large IPSs would start accumulating multiple /32s, then routing concerns would come back, and largest ISPs will start aggregating to /28s or /24s or whatnot. That is still a whole lot of addresses (and IPv4 still looks laughably small in comparison), but actual, practical numbers are way, way lower then "340 undecillion" marketing figure being plastered all over the place.

km3k 11y ago
From what I've read, most end users will get /56 blocks and larger organizations will be the ones to get a /48, so the potential end users is much higher than you've estimated.
- aexaey 11y ago
  Blanket policy of /48 per end user comes from a (now obsolete) RFC3177. All RIRs now have less generous recommendations - both RIPE [0] and ARIN [1] seem to operate in /56 granularity nowadays, which is a very sensible step forward of course. [0] https://www.ripe.net/publications/docs/ripe-650 https://www.ripe.net/publications/docs/ripe-650 [1] https://www.arin.net/policy/nrpm.html#six7 https://www.arin.net/policy/nrpm.html#six7