IP4 Space

Christopher Morrow morrowc.lists at gmail.com
Mon Mar 22 19:42:31 CDT 2010

On Mon, Mar 22, 2010 at 3:53 PM, Stan Barber <sob at academ.com> wrote:
> In this case, I am talking about an IPv6<->IPv6 NAT analogue to the current IPv4<->IPv4
> NAT that is widely used with residential Internet service delivery today.

I don't necessarily see 6-6 nat being used as 4-4 is today, but I do
think you'll see 6-6 nat in places. the current ietf draft for 'simple
cpe security' (draft-ietf-v6ops-cpe-simple-security-09.txt) is
potentially calling for some measures like nat, not nat today but...

> I believe that with IPv6 having much larger pool of addresses and each residential
> customer getting a large chunk of addresses will make  IPv6<->IPv6 NAT unnecessary. I
> also believe that there will be IPv6 applications that require end-to-end communications
> that would be broken where NAT of that type used. Generally speaking, many users of

I think you'll see apps like this die... quickly, but that's just my opinion.

> the Internet today have not had the luxury to experience the end-to-end model because of
> the wide use of NAT.
> Given that these customers today don't routinely multihome  today, I currently believe
> that behavior will continue. Multihoming is generally more complicated and expensive

That's not obvious. if a low-cost (low pain, low price) means to
multihome became available I'm sure it'd change... things like
shim-6/mip-6 could do this.

> than just having a single connection with a default route and most residential customers
> don't have the time, expertise or financial support to do that. So, the rate of multihoming
> will stay about the same even though the number of potential sites that could multihome
> could increase dramatically as IPv6 takes hold.
> Now, there are clearly lots of specifics here that may change over time concerning what
> the minimum prefix length for IPv6 advertisements might be acceptable in the DFZ (some
> want that to be /32, other are ok with something longer). I don't know how that will change
> over time. I also think that that peering will continue to increase and that the prefix
> lengths that peers will exchange with each other are and will continue to be less
> constrained by the conventions of the DFZ since the whole point of peering is to be
> mutually beneficial to those two peers and their customers. But, that being said, I don't
> think residential customers will routinely do native IPv6 peering either. I think IP6-in-IPv4
> tunneling is and will continue to be popular and that already makes for some interesting
> IPv6 routing concerns.

I firmly hope that ipv6-in-ipv4 dies... tunnel mtu problems are
horrific to debug.
(we'll see though!)

> Hope that clarifies my comment for you. Obviously, they are my opinions, not facts. The
> future will determine if I was seeing clearly or was mistaken in how these things might
> unfold. However, I think a discourse about these possibilities is helpful in driving
> consensus and that's one of the valuable things about mailing lists like this.
> On Mar 18, 2010, at 8:20 PM, Christopher Morrow wrote:
>> On Thu, Mar 18, 2010 at 7:36 PM, Stan Barber <sob at academ.com> wrote:
>>> Ok. Let's get back to some basics to be sure we are talking about the same things.
>>>  First, do you believe that a residential customer of an ISP will get an IPv6 /56 assigned for use in their home? Do
>>> you believe that residential customer will often choose to multihome using that prefix? Do you believe that on an
>>> Internet that has its primary layer 3 protocol is IPv6 that a residential customer will still desire to do NAT for reaching
>> how are nat and ipv6 and multihoming related here? (also 'that has a
>> primary layer 3 protocol as ipv6' ... that's a LONG ways off)
>> -chris
>>> IPv6 destinations?
>>> I am looking forward to your response.
>>> On Mar 18, 2010, at 2:25 PM, William Herrin wrote:
>>>>> On Mar 5, 2010, at 7:24 AM, William Herrin wrote:
>>>>>> Joel made a remarkable assertion
>>>>>> that non-aggregable assignments to end users, the ones still needed
>>>>>> for multihoming, would go down under IPv6. I wondered about his
>>>>>> reasoning. Stan then offered the surprising clarification that a
>>>>>> reduction in the use of NAT would naturally result in a reduction of
>>>>>> multihoming.
>>>> On Thu, Mar 18, 2010 at 11:07 AM, Stan Barber <sob at academ.com> wrote:
>>>>> I was not trying to say there would be a reduction in multihoming. I was
>>>>> trying to say that the rate of increase in non-NATed single-homing
>>>>> would increase faster than multihoming. I guess I was not very clear.
>>>> Hi Stan,
>>>> Your logic still escapes me. Network-wise there's not a lot of
>>>> difference between a single-homed  IPv4 /32 and a single-homed IPv6
>>>> /56. Host-wise there may be a difference but why would you expect that
>>>> to impact networks?
>>>> Regards,
>>>> Bill Herrin
>>>> --
>>>> William D. Herrin ................ herrin at dirtside.com  bill at herrin.us
>>>> 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
>>>> Falls Church, VA 22042-3004

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