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

Christopher Morrow morrowc.lists at gmail.com
Wed Dec 4 18:35:26 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).
>
> 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?



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