Re: Confirmation to advance: draft-ietf-6man-ipv6only-flag-05

[Philip Homburg <[e-mail]>]

>Most usually, it's not sites that decide to use link-locals, but hosts.
>-- it's a host-side policy that is *not* selected or configured on a
>per-network basis.
>
>That said, in all cases, I expect the network to "just work". Users
>should not be required to understand this sort of technical details for
>them to get a good experience.

Networks don't 'just work', except in rare cases of completely disconnected
networks.

Today the vast majority of all networks has some kind of router. And in 
simple cases like CPEs, they get configuration from the network. My proposal
is specifically in the case a router provides IPv6 connectivity.

If we now tell hosts to stop doing IPv4 links local in that case (i.e. when
IPv6 connectivity is available) then that can save us a lot of headaches
later.

Of course, can choose to not that, just in case in the future a legacy IPv4
printer is around on an IPv6-only network. But in that case we will have to
live with the mess of hosts trying to do service discovery using IPv4 
link local until forever.

If we say: in the context of IPv6, DHCPv4 signals the presence of native IPv4
on a link, then we make it easy for hosts to figure out what is going on.
We also make it easy to get rid of IPv4.

For users that doesn't matter. The CPE can easily have a DHCPv4 server
that will be on by default in the near future and will be off by default
later. And will be dropped completely when there is no IPv4 support anymore.

In managed networks, it makes clear that if the network admin wants IPv4
there is a DHCPv4 server/relay. Without DHCPv4 server, there should be no
IPv4.

Finally, on completely disconnected networks the situation would be unchanged,
so directly connecting a laptop to an IPv4-only printer would work.