Re: [RFC] Multicast and IPv6 Link Local Addresses

["Dan Lüdtke" <mail@danrl.com>]

Hi everyone,

I am very excited that we have this discussion, as I am one of those =
IPv6-first/IPv6-only guys who like poking the topic.
I try to keep it short:

- Scalability: I agree with what George said. Broadcast does not scale =
nicely, and IPv6 multicast is intended to help scaling things by =
reaching exactly the node that need to get a copy of a particular =
packet. Downgrading IPv6 multicast to broadcast hurts scalability and I =
for one, would rather not see multicast in WireGuard if it does not =
scale. I am afraid it would be counterproductive to the goal of having a =
widely accepted and used protocol.

- Multicast is not the everyday use case, so if multicast requires an =
extra knob or an extra option, that would be fine I guess. I am in favor =
of intentionally enabling multicast. I am still wrapping my head around =
static vs. dynamic (read: magic) configuration of multicast addresses =
and groups. Will let you know once I end up with something worth =
sharing. In the meantime, I think "solicited node multicast =
addresses/groups" are the one thing that comes with the least amount of =
trouble. Especially if IPv6 LL addressing is also there.

- IPv6 link-local addressing: For me it is a perfect example for "the =
right amount of magic". It would make (at least my) life so much easier. =
Filling the neighbor cache would require WireGuard to provide (simulated =
or real) solicited node multicast addresses routing, right? Or is it =
feasible to fill the neighbor cache based on the peer configuration? The =
last thing sounds wrong to me.

So much for my first thoughts.

Cheers,

Dan=