Re: [IPv6] Architectural comments on draft-ietf-6man-ipv6-over-wireless-

[Ted Lemon <[e-mail]>]

On Thu, Jul 27, 2023 at 2:24 PM Pascal Thubert (pthubert) <
[e-mail]> wrote:

> I have a large building or campus. I want to enter anywhere and obtain an
> address that I can use throughout the campus without renumbering when I go
> to the next building/ level/room.
>

Why do you want that? I go to buildings like this all the time. My IP
address changes when I move around. Things work just fine.


> Otoh I want that bonjour always finds the nearest printer and that printer
> is in the same room as me or in a closeby room. Certainly not anywhere in
> the campus.
>

I get that you want that, but that's an app-layer problem. You want to ask
the app layer "where is the closest printer to me," or (in my case) "where
is the printer near my office?"


> For the latter the admin sets the broadcast domain to be limited to a
> small area in the building.
>

It's just an accident that mDNS usually gives you the "closest printer"
answer as long as you aren't doing weird IP mobility complexity. We
shouldn't try to solve that problem by weird broadcast-domain-scope
shaping. It feels like you are creating a problem that then needs to be
solved here.

For the former your subnet must still be reachable in the room you’re in.
> So the desired range / coverage of the subnet does not match the physical
> space covered by the broadcast domain you’re in.
>

Why do I want this? I don't want this!


> From there you have to choices. 1)  Tunnel selected packets like MIPv6
> does to where you entered the building. Or 3) route. Obviously since the
> use case is a real customer situation we implemented 1) and that’s an awful
> hack.
>

Or 4) have numbering and the broadcast domain be local to wherever you
happen to be at the moment, which is what we do now.


> The architecture provides a model that allows decoupling the broadcast
> domain that you link local address will reach from the subnet where your
> address will be topologically correct and reachable.
>
> Right. What I asked in my previous message, which you haven't answered, is
"what actual organization wants this, and why?" E.g., if the reason they
want this is because they've been sold a weird network setup that doesn't
work well, maybe the fix is to fix that rather than making things /even
more/ complicated in order to maybe get back to where things would have
been if you'd just used reasonable subnet sizes tied to network
infrastructure.