Naive IPv6 (was AT&T UVERSE Native IPv6, a HOWTO)

Brian Dickson brian.peter.dickson at gmail.com
Wed Dec 4 19:23:56 UTC 2013


On Wed, Dec 4, 2013 at 1:32 PM, Rob Seastrom <rs at seastrom.com> wrote:

>
> Brian Dickson <brian.peter.dickson at gmail.com> writes:
>
> > Rob Seastrom wrote:
> >
> >> "Ricky Beam" <jfbeam at gmail.com<
> http://mailman.nanog.org/mailman/listinfo/nanog>>
> >> writes:
> >> >
> >> * On Fri, 29 Nov 2013 08:39:59 -0500, Rob Seastrom <rs at seastrom.com
> >> <http://mailman.nanog.org/mailman/listinfo/nanog>> wrote: *>>
> >> * So there really is no excuse on AT&T's part for the /60s on uverse
> >> 6rd... *>
> >> * ... *>
> >> * Handing out /56's like Pez is just wasting address space -- someone *>
> >> * *is* paying for that space. Yes, it's waste; giving everyone 256 *>
> >> * networks when they're only ever likely to use one or two (or maybe *>
> >> * four), is intentionally wasting space you could've assigned to *>
> >> * someone else. (or **sold** to someone else :-)) IPv6 may be huge to *>
> >> * the power of huge, but it's still finite. People like you are *>
> >> * repeating the same mistakes from the early days of IPv4... * There's
> >> finite, and then there's finite. Please complete the
> >> following math assignment so as to calibrate your perceptions before
> >> leveling further allegations of profligate waste.
> >> Suppose that every mobile phone on the face of the planet was an "end
> >> site" in the classic sense and got a /48 (because miraculously,
> >> the mobile providers aren't being stingy).
> >> Now give such a phone to every human on the face of the earth.
> >> Unfortunately for our conservation efforts, every person with a
> >> cell phone is actually the cousin of either Avi Freedman or Vijay
> >> Gill, and consequently actually has FIVE cell phones on active
> >> plans at any given time.
> >> Assume 2:1 overprovisioning of address space because per Cameron
> >> Byrne's comments on ARIN 2013-2, the cellular equipment providers
> >> can't seem to figure out how to have N+1 or N+2 redundancy rather
> >> than 2N redundancy on Home Agent hardware.
> >> What percentage of the total available IPv6 space have we burned
> >> through in this scenario? Show your work.
> >> -r
> >
> >
> > Here's the problem with the math, presuming everyone gets roughly the
> same
> > answer:
> > The efficiency (number of prefixes vs total space) is only achieved if
> > there is a "flat" network,
> > which carries every IPv6 prefix (i.e. that there is no aggregation being
> > done).
> >
> > This means 1:1 router slots (for routes) vs prefixes, globally, or even
> > internally on ISP networks.
> >
> > If any ISP has > 1M customers, oops. So, we need to aggregate.
> >
> > Basically, the problem space (waste) boils down to the question, "How
> many
> > levels of aggregation are needed"?
> >
> > If you have variable POP sizes, region sizes, and assign/aggregate
> towards
> > customers topologically, the result is:
> > - the need to maintain power-of-2 address block sizes (for aggregation),
> > plus
> > - the need to aggregate at each level (to keep #prefixes sane) plus
> > - asymmetric sizes which don't often end up being just short of the next
> > power-of-2
> > - equals (necessarily) low utilization rates
> > - i.e. much larger prefixes than would be suggested by "flat" allocation
> > from a single pool.
> >
> > Here's a worked example, for a hypothetical big consumer ISP:
> > - 22 POPs with "core" devices
> > - each POP has anywhere from 2 to 20 "border" devices (feeding access
> > devices)
> > - each "border" has 5 to 100 "access" devices
> > - each access device has up to 5000 customers
> >
> > Rounding up each, using max(count-per-level) as the basis, we get:
> > 5000->8192 (2^13)
> > 100->128 (2^7)
> > 20->32 (2^5)
> > 22->32 (2^5)
> > 5+5+7+13=30 bits of aggregation
> > 2^30 of /48 = /18
> > This leaves room for 2^10 such ISPs (a mere 1024), from the current /8.
> > A thousand ISPs seems like a lot, but consider this: the ISP we did this
> > for, might only have 3M customers.
> > Scale this up (horizontally or vertically or both), and it is dangerously
> > close to capacity already.
> >
> > The answer above (worked math) will be unique per ISP. It will also drive
> > consumption at the apex, i.e. the size of allocations to ISPs.
> >
> > And root of the problem was brought into existence by the insistence that
> > every network (LAN) must be a /64.
> >
> > That's my 2 cents/observation.
> >
> > Brian
>
> At a glance, I think there's an implicit assumption in your
> calculation that each ISP has to be able to hold the whole world
> (unlikely) and/or there is no such thing as mobile IP or any other
> kind of tunneling technology going on within the mobile network (also
> wrong from everything I understand).
>
>
No, not the whole world, just that the combo of internal+external has to
fit.
If internal breaks the table, external is irrelevant, and flat/unaggregated
would do that.

As for tunneling - not sure that will hold forever, especially depending on
the degree
of stretch (contributes to latency and bandwidth doubling).


> Also, I'm not sure where "from the current /8" comes from, as there's
> a /3 in play (1/8 of the total space, maybe that was it?) and each
> RIR is getting space in chunks of /12...
>
>
Doh! (I knew there was an "8" involved - need more caffeine). You're right,
of course.


> Re-working your conclusion statement without redoing the math, "This
> leaves room for 2^15 such ISPs (a mere 16384), from the current /3."
>
> Oddly enough, I'm OK with that.  :)
>
>
It's not dire, but I'd be more comfortable with a few more zeros in there
(even one more zero).

But my point was that every 10* multiplier is 2^3-ish, and in order to get
to the numbers you were pointing to, there are several of those involved.
E.g. In order to provide 68B instead of 3M, which my math worked out to,
that is 23000-ish bigger.
That is any combination of more and/or bigger ISPs.

Flatter networks (mobile) helps, but to what degree will fixed non-tunnel
ISPs contribute, is the real question?
What percentage of 68B will have non-wireless service(s)?

Brian


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