> On Apr 16, 2020, at 08:42 , John Curran <[email protected]> wrote:
>
> On 24 Mar 2020, at 1:20 PM, ARIN <[email protected] <mailto:[email protected]>> wrote:
>> ...
>> Reserving /40s only for organizations initially expanding into IPv6 from an
>> initial sliver of IPv4 space will help to narrowly address the problem
>> observed by Registration Services while avoiding unintended consequences by
>> accidentally giving a discount for undersized allocations.
>
> ARIN tries to provide as much flexibility as possible in dealing with
> requests, so it is important that the community document the reasoning behind
> policy language that constrains the choices available to those requesting
> resources. ARIN staff will certainly get asked about such restrictions, so
> we best understand the motivation.
>
> For this reason, would it be possible for the advocates of the policy to
> elaborate (on the list) on the perceived "unintended consequences by
> accidentally giving a discount for undersized allocations”? (In particular,
> if a party specifically sought a /40 IPv6 allocation but they held more than
> /24 of IPv4, is the desire that ARIN would deny the request if they failed to
> agree to a larger IPv6 allocation or agree to divesture of IPv4 resources
> down to the /24 maximum?)
Frankly, I wouldn’t even want to allow access to this option through
divestiture of their IPv4 holdings.
I look at it this way.. Originally, we wanted ISPs to have a minimum /32 in
order to maximize aggregation while still providing reasonably good support for
handing out /48s to every subscriber end site regardless of size.
Then, because there were unintended consequences of IPv4<->IPv6 fee structure
alignment, we put in place a mechanism to allow that down to /36 if the ISP
really wanted to do that to avoid the fee increase.
Now, we’re talking about going down another nibble.
A /40 is only 256 /48s and you have to account for the ISPs infrastructure
within that too.
For an ISP running their entire customer base on a single /24, that might not
have any unintended consequences, but even in that case, there’s the risk that
said ISP has more than a couple hundred customers behind that /24 via various
forms of address sharing (NAT and worse), in which case a /40 simply won’t
provide the desired IPv6 policy outcome of /48s for everyone.
Admittedly, /48s for everyone still isn’t gaining as much traction as we’d like
due to a combination of IPv4-think at some ISPs and other reasons I have
trouble understanding.
E.G. I once had a discussion with the IPv6 project manager for a major $CABLECO
about why they were sticking it to their residential customers with a maximum
/60 instead of a /48. His answer perplexed me… He said that the problem was
that if they gave out /48s to all their customers the way their network is
structured, they’d need a /12. Now I realize that policy only allows ARIN to
give out a /16 at a time, but I’m quite certain this particular organization
could easily qualify for 16 /16s without any issue whatsoever. When I pointed
this out, he just walked away shaking his head.
Now I realize a /12 sounds like a ridiculous amount of space, but if you think
about it, this is an organization that has several /8s worth of IPv4, so it’s
not actually all that far fetched. Also, I seriously doubt that there are
anywhere near 100 organizations with the number of customers this $CABLECO has.
There are 512 /12s in 2000::/3 which is just the first 1/8th of IPv6 address
space designated as GUA (Global Unicast Addresses). The math works. We have the
address space to do this and give everyone /48s without any issue of running
out.
So… we have a circumstance of competing tradeoffs in policy:
1. We don’t want policy to create perverse incentives to not give
/48s to customers. That’s one of the reasons
for the particular wording of the PAU text in the IPv6 ISP
policy (which staff doesn’t do a particularly good
job of following in my observation).
2. We don’t want to create economic disincentives to IPv6
deployment.
This policy is an effort to reduce issue number 2 at the cost of potentially
exacerbating issue number 1. We’d very much like to minimize the extent to
which that unintended exacerbation of issue number 1 occurs.
Owen
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