Re: Back to work

[Christian Huitema <[e-mail]>]

On 10/28/2020 5:17 PM, Jana Iyengar wrote:
> I like the universality of the 3x limit. The reasoning applies broadly
> and there's no reason to separately reason about how a server responds
> to new addresses, be it at the start of a connection or
> mid-connection. Overall, I have a few minor suggestions to make, but
> I'm happy with the way the PR is headed.


I think that we can devise proper solutions for "organized migrations",
such as requiring both receipt and acknowledgement of a long enough
packet before validating a path. I am not going to belabor that. But NAT
traversal is a can of worms, and some of the norms are going to bite us.

I order to support NAT traversal, we request servers to take action if
they see a packet arriving from a new address of the client. This opens
a huge hole through which enterprising MOTS or "specially crafted
clients" can harass servers. We have an OK defense: send a challenge to
both old and new IP to force "proof of address ownership". That defense
is OK because it uses minimal length packets, and thus does not cause
too much amplification. I think we should leave it at that, and not
force the server to send large packets. There is a need to then validate
that the path can carry traffic, which will happen naturally when the
server tries to send a large packet. But if the server only sends these
large packets after address ownership has been verified, things ought to
be quite good.

-- Christian Huitema