Re: [v6ops] ULA precedence [Thoughts about wider operational input]

[Nick Buraglio <[e-mail]>]

On Sun, Apr 24, 2022 at 7:16 PM Lorenzo Colitti <[e-mail]> wrote:

> On Mon, Apr 25, 2022 at 2:28 AM Erik Auerswald <[e-mail]>
> wrote:
>
>>  "Since ULAs are defined to have a /48 site prefix, an implementation
>>   might choose to add such a row automatically on a machine with
>>   a ULA."
>>
>> The result is that only the local ULA prefix, i.e., exactly the
>> local IPv6 addresses, are preferred over IPv4 (and IPv6 GUA).
>> This should be exactly what is needed to use ULA addresses inside
>> an organization, or for a lab.
>> [...]
>> Implementing the non-normative suggestion from Section 10.6 of RFC
>> 6724 would in all likelihood result in making ULA usable for local
>> tests and even first steps in deploying IPv6.  ULA addresses would
>> only be used locally.  Existing IPv4 based Internet access would not
>> be impaired by adding IPv6 ULA.
>>
>
> That does seem like it might make ULA more useful, yes.
>
> Additionally, maybe we could clarify that the longest-prefix match rule
> does not apply to ULAs outside the same /48? I think that would fix the
> issue observed by +Ted Lemon <[e-mail]> in home networks:
> https://datatracker.ietf.org/meeting/113/materials/slides-113-6man-source-address-selection-for-foreign-ulas-00
> .
>

I also have data that supports the longest match not applying to ULA.

>
>
>> In order to keep IPv6 deployment similar to IPv4, IPv6 NAT could be
>> considered.  To make this work as intended, the address selection
>> policy table could be adjusted to contain the local ULA prefix
>> with precedence greater or equal to GUA and the same label as GUA.
>>
>
> This seems like it would encourage the use of IPv6 NAT. I think there is
> reasonably strong consensus within the IETF that that is not the right way
> to go, because it pushes problems on to application developers. This adds
> costs for NAT traversal software development and maintenance, and requires
> devices to implement NAT keepalives, increasing battery usage.
>


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