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

Rob Seastrom rs at seastrom.com
Wed Dec 4 18:32:33 UTC 2013


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).

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...

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.  :)

-r




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