Re: [babel] Mirja Kühlewind's Discuss on draft-ietf-babel-dtls-07: (with DISCUSS and COMMENT)

[Mirja Kuehlewind <[e-mail]>]

> On 8. Aug 2019, at 13:17, Juliusz Chroboczek <[e-mail]> wrote:
> 
>>> Using an ephemeral port that is discovered at runtime would add a failure mode
>>> to the protocol and make it less robust.
> 
>> Can you please explain why that would make it less robust? I would
>> actually think that is would make it more robust. In any case you need
>> to somehow discovery the neighbour. Usually the babel HELLO would be
>> used for that. When you add an new TLV to that HELLO that indicates
>> a port that should be used for DTLS, this also gives you and additional
>> indication that the peer sending the hello actually supports DTLS which
>> I believe would make it more robust.
> 
> That's an intruiguing idea.
> 
>> Further with respect to security and topics probably recently discussed, not having a default port would make it harder for an attacker to flood a route with DTLS handshakes on that port.
> 
> Could you please explain what happens if an attacker sends out 65535
> spoofed multicast Hellos indicating 65535 distinct ports?

You maybe rate limit DTLS connection attempts…? I didn’t fully design the protocol here but would like the wg to consider such an approach. However, I guess it might make sense to even rate limit in the proposed approach, or cache for a certain time that a connection attempt to a certain peer failed before trying again.

Mirja


> 
> -- Juliusz
> 
>