Re: [IPv6] Adoption call for draft-bctb-6man-rfc6296-bis

[Mark Smith <[e-mail]>]

On Mon, 18 Mar 2024, 18:42 Brian E Carpenter, <[e-mail]>
wrote:

> On 18-Mar-24 21:35, Mark Smith wrote:
> > On Mon, 18 Mar 2024 at 18:03, Ted Lemon <[e-mail]> wrote:
> >>
> >> Right. In fact I think we recommend that for the home router use case
> already. Sorry, I was really trying to figure out a reason why we’d want
> this, but internal ULA handles the “no renumbering” concern, so that’s not
> a reason.
> >>
> >
> > ULAs won't solve the renumbering problem after
> > draft-ietf-6man-rfc6724-update (and doesn't  with RFC 6724).
> >
> > Once GUAs are preferred over ULAs by default, then GUAs will
> > automatically be used when ULAs are available to reach a host, if they
> > share a single DNS/mDNS name.
> >
> > A host could have 2 distinct DNS names, one for the ULA address, and
> > one for the GUA address, however that makes the first step of
> > Destination Address selection an unstated and unfriendly one, each and
> > every time - a human takes the first DA selection step, deciding which
> > DNS name they use for the host.
> >
> > Happy Eyeballs v3 won't solve this problem either, it uses
> > RFC6724(-update) sort order to choose which IPv6 addresses to attempt
> > to connect to first, so GUA will be chosen first (and of course Happy
> > Eyeballs doesn't get supplied with or chooses between 2 DNS names for
> > the same node.)
>
> HE v3 can still be changed. See the discussion a few months ago about
> get_addr_pairs() for example.
>
> https://github.com/becarpenter/getapr/blob/main/ProofOfConcept.md


I don't think it needs to be charged. It's primary purpose is to deal with
reachability problems in the presence of a DNS entry with multiple IPv6
and/or IPv4 addresses.

Why not let HE deal with the rarely unreachable ULAs if somebody
erroneously puts them in global DNS, or when a ULA much be unreachable for
some other reason.

RFC 6724 got 2 things wrong:

- put ULAs below IPv4

- put ULAs below GUAs

RFC6724-update only fixes one of those problems.

ULAs are the replacement for site-locals, just without the ambiguity of
site-locals.

Site-locals were preferred over GUAs, due to the scope comparison. ULAs,
being the direct replacement for site-locals, should also be preferred over
GUAs (not via a scope check, however the outcome should be the same).

I think anybody who takes the position that the first IPv6 DA returned by
getaddrinfo() must work, which is implied by GUAs being preferred over
ULAs, is really saying the following:

- IPv6 hosts should only ever have a single address, because having
multiple addresses implies that multiple addresses are needed because there
may be reachability problems to act if those addresses.

- getaddrinfo() only needs to return a single IPv6 address for any and all
DNS look ups, making DA/SA selection much simpler.

- Happy Eyeballs only needs to attempt to connect to a single IPv6 address
and a single IPv4 address, also making HE simpler.

- Multipath transport layer protocols have no value since there would only
be a single IPv6 address to connect to on a host.

Regards,
Mark.


>
>      Brian
>
> >
> > Regards,
> > Mark.
> >
> >> Op ma 18 mrt 2024 om 16:37 schreef Lorenzo Colitti <[e-mail]>
> >>>
> >>> On Mon, Mar 18, 2024 at 4:09 PM Ted Lemon <[e-mail]> wrote:
> >>>>
> >>>> On Mon, Mar 18, 2024 at 3:53 PM Michael Richardson <
> [e-mail]> wrote:
> >>>>>
> >>>>> I agree.
> >>>>> We had 6RENUM WG sometime ago.
> >>>>> (It's confusing that "RENUM" BOF has no link to 6RENUM in the
> datatracker)
> >>>>
> >>>>
> >>>> I think we were a bit naive when we did that work. I think if we want
> renumbering to be usable, we actually need to account for all the
> configuration data that contains IPv6 addresses, and I don't think we did
> that. Dynamically regenerating the entire distributed configuration
> database whenever our prefix changes is very difficult to get right. We
> need a solution that's on the same level of difficulty as RA, not a giant
> distributed database problem.
> >>>
> >>>
> >>> A better solution to this problem is to run both ULA and global space.
> Internal resources and networks can use ULAs and will never need to be
> renumbered. Client-facing links can additionally have global addresses
> configured. Those do need to be renumbered when changing ISPs, but no
> databases need to be updated.
> >>
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