Last Call Review of draft-ietf-babel-dtls-06
review-ietf-babel-dtls-06-rtgdir-lc-rogge-2019-07-05-00

//resend to RTG DIR list
Hi,

I was asked by the Routing Directorate to do a last call review of
draft-ietf-babel-dtls-06.

I like that the draft is quite short, which is a good thing for a
security draft. I have found a few question you can consider to
address in the final document.

Chapter 2.3:
I wonder if using DTLS protected unicast Hellos should be mandatory...
using unprotected multicast to determine bidirectional reachability
looks like a good way to do a cheap denial of service attack.

Chapter 2.5:
What happens when a node starts a new DTLS connection and there is
already one in the neighbor table? This could both be an attempt to
attack Babel, a reboot of a node or just a matter of misconfiguration
of two nodes.

Chapter 3:
Different pairs of nodes could select different ciphers, resulting in
different MTUs. I assume this is no problem for Babel (could be
mentioned in the chapter).

Some of the design decisions of regarding the three questions could be
mentioned in chapter 5 (Security Implications).

Henning Rogge