Re: Automatically connecting to stub networks...

[Michael Richardson <[e-mail]>]

Ted Lemon <[e-mail]> wrote:
    > On Dec 3, 2020, at 1:25 PM, Michael Richardson <[e-mail]> wrote:
    >> I'm assuming that it's the gateway that does DHCPv6-PD.
    >> If that works, then we are done.

    > Not quite. We still need to advertise reachability to the prefix, and
    > do all the work to set up numbering on the local link. Assume no
    > management, and an arbitrary number of stub routers potentially
    > connecting to an 802.15.4 mesh. How does DHCPv6-PD even work in this
    > scenario? I’m not saying it can’t, but it’s not “just do DHCPv6-PD”!

I guess I'm confused.
1) If the home router speaks IPv6, then it's already numbered the "LAN" link.

2) If it speaks DHCPv6-PD server, then when it allocates a prefix to the
802.15.4 router that asked for the prefix, then it sets up reachability.
{Of course, this fails if there are multiple gateways, a la homenet, but I
think that's out of scope for this situation}

What else is there?
It's true that the DHCPv6-RELAY stuff is a mess for PD, but there shouldn't
be any DHCPv6-relaying in a home.

{While the home gateway might have to go back to the ISP for another /64,
that's not a local problem.}

    >> We don't necessarily need the ULA or the NAT64 at that point.
    >> (Although, the delegated prefix might not be a GUA.)

    > Right, have to account for that. Also probably should account for the
    > case where the infrastructure network provides NAT64 via ipv4only.arpa,
    > so we don’t have to do it in the border router. This is obviously
    > HIGHLY preferable. :)

Yes.
Basically, the border router should probably do reachability checks to see if
it can get to the cloudy places it cares about on both IPv4 and IPv6, and
then enable whatever it needs to make things work.
I think that this would make a really nice operational BCP document.

    >> It's when it does not work that I think your draft comes into play.
    >> One is essentially bring IPv6 to a LAN where there might not any.
    >> I think that's okay.
    >> {I also think that the thing bring that ULA to the LAN should be a DHCPv6-PD
    >> server as well: there could be another gateway that needs IPv6}

    > We have to use what we’re given. If there’s DHCPv6-PD, we should figure
    > out a way to use that. The Apple solution is very careful not to add
    > anything to the network that’s unnecessary—if  you have a prefix from
    > your ISP, it doesn’t advertise an IPv6 prefix on the infrastructure
    > link, because there’s already a usable prefix.

Good!
I think we are in violent agreement.

--
Michael Richardson <[e-mail]>   . o O ( IPv6 IøT consulting )
           Sandelman Software Works Inc, Ottawa and Worldwide