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

Christopher Morrow morrowc.lists at gmail.com
Wed Dec 4 19:46:49 UTC 2013


On Wed, Dec 4, 2013 at 2:25 PM, Brian Dickson
<brian.peter.dickson at gmail.com> wrote:
> Not necessarily transit - leaf ASN ISP networks (which do IP transit for
> consumers, but do not have BGP customers) would also be counted in. They do
> still exist, right?

that's still a transit as, right? I think your math means that there
would only ever be 16k networks.. which seems small.


> On Wed, Dec 4, 2013 at 1:35 PM, Christopher Morrow <morrowc.lists at gmail.com>
> wrote:
>>
>> 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).
>> >
>> > 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.  :)
>>
>> 16384 'isp' which is really 'transit asn' right?
>
>



More information about the NANOG mailing list