Dual stack IPv6 for IPv4 depletion

George Metz george.metz at gmail.com
Wed Jul 15 19:43:14 UTC 2015


On Wed, Jul 15, 2015 at 2:11 PM, Doug Barton <dougb at dougbarton.us> wrote:

> On 7/15/15 8:20 AM, George Metz wrote:
>
>>
>>
Snip!


> Also, as Owen pointed out, the original concept for IPv6 networking was a
> 64 bit address space all along. The "extra" (or some would say, "wasted")
> 64 bits were tacked on later.
>
>  Still oodles of addresses, but worth
>> noting and is probably one reason why some of the "conservationists"
>> react the way they do.
>>
>
> It's easy to look at the mandatory /64 limit and say "See, the address
> space is cut in half to start with!" but it's not accurate. Depending on
> who's using it a single /64 could have thousands of devices, up to the
> limit of the broadcast domain on the network gear. At minimum even for a
> home user you're going to get "several" devices.


Allow me to rephrase: "A single /32 could have thousands of devices, up to
the limit of a 10/8 NATted behind it". This, plus the fact that it WAS
originally 64-bit and was expanded to include RA/SLAAC, is why I chose that
analogy.


>  Next, let's look at the wildest dreams aspect. The current
>> "implementation" I'm thinking of in modern pop culture is Big Hero 6
>> (the movie, not the comics as I've never read them). Specifically,
>> Hiro's "microbots". Each one needs an address to be able to communicate
>> with the controller device. Even with the numbers of them, can probably
>> be handled with a /64, but you'd also probably want them in separate
>> "buckets" if you're doing separated tasks. Even so, a /48 could EASILY
>> handle it.
>>
>
> Right, 65k /64s in a /48.
>
>  Now make them the size of a large-ish molecule. Or atom. Or protons.
>> Nanotech or femtotech that's advanced enough gets into Clarke's Law -
>> any sufficiently advanced technology is indistinguishable from magic -
>> but in order to do that they need to communicate. If you think that
>> won't be possible in the next 30 years, you probably haven't been paying
>> attention.
>>
>
> I do see that as a possibility, however in this world that you're
> positing, how many of those molecules need to talk to the big-I Internet?
> Certainly they need to communicate internally, but do they need routable
> space? Also, stay tuned for some math homework. :)


So, you're advising that all these trillions of nanites should, what, use
NAT? Unroutable IP space of another kind? Why would we do that when we've
already got virtually unlimited v6 address space?

See what I mean? Personally I'd suspect something involving quantum states
would be more likely for information passage, but who knows what the end
result is?


> I wrote my email as a way of pointing out that maybe the concerns (on
>> both sides)- aren't baseless,
>>
>
> Please note that I try very hard not to dismiss anyone's concerns as
> baseless, whether I agree with them or not. As I mentioned in my previous
> message, I believe I have a pretty good understanding of how the "IPv6
> conservationists" think. My concern however is that while their concerns
> have a basis, their premise is wrong.


I wasn't intending yourself as the recipient keep in mind. However, IS
their premise wrong? Is prudence looking at incomprehensible numbers and
saying "we're so unlikely to run out that it just doesn't matter" or is
prudence "Well, we have no idea what's coming, so let's be a little less
wild-haired in the early periods"? The theory being it's a lot harder to
take away that /48 30 years from now than it is to just assign the rest of
it to go along with the /56 (or /52 or whatever) if it turns out they're
needed. I personally like your idea of reserving the /48 and issuing the
/56.


> So you asked an interesting question about whether or not we NEED to give
> everyone a /48. Based on the math, I think the more interesting question
> is, what reason is there NOT to give everyone a /48? You want to future
> proof it to 20 billion people? Ok, that's 1,600+ /48s per person. You want
> to future proof it more to 25% sparse allocation? Ok, that's 400+ /48s per
> person (at 20 billion people).
>
> At those levels even if you gave every person's every device a /48, we're
> still not going to run out, in the first 1/8 of the available space.
>
>  Split the difference, go with a /52
>>
>
> That's not splitting the difference. :)  A /56 is half way between a /48
> and a /64. That's 256 /64s, for those keeping score at home.
>

It's splitting the difference between a /56 and a /48. I can't imagine
short of the Nanotech Revolution that anyone really needs eight thousand
separate networks, and even then... Besides, I recall someone at some point
being grumpy about oddly numbered masks, and a /51 is probably going to
trip that. :)

I think folks are missing the point in part of the conservationists, and
all the math in the world isn't going to change that. While the... let's
call them IPv6 Libertines... are arguing that there's no mathematically
foreseeable way we're going to run out of addresses even at /48s for the
proverbial soda cans, the conservationists are going, "Yes, you do math
wonderfully. Meantime is it REALLY causing anguish for someone to only get
256 (or 1024, or 4096) networks as opposed to 65,536 of them? If not, why
not go with the smaller one? It bulletproofs us against the unforeseen to
an extent."

As an aside, someone else has stated that for one reason or another IPv6 is
unlikely to last more than a couple of decades, and so even if something
crazy happened to deplete it, the replacement would be in place anyhow
before it could. I would like to ask what about the last 20 years of IPv6
adoption in the face of v4 exhaustion inspires someone to believe that just
because it's better that people will be willing to make the change over?



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