Review of RA Guard, draft-vandevelde-v6ops-ra-guard-01

[Christian Vogt <christian.vogt@nomadiclab.com>]

Gunter, Eric, Ciprian, Janos,

I read your RA Guard proposal, and I believe this will be a very
useful feature.  Especially the simple operational mode, in which
Router Advertisement messages are allowed only on manually
pre-configured ports, would provide a good level of security at low
cost.  Two comments, nevertheless:

(1)  The RA Guard currently has two separate state machines, one for
     the RA Guard device itself, and one on the per-interface level.  I
     do not see a convincing need for having two state machines instead
     of one.  It seems that you want the RA Guard to operate on a
     per-interface basis, and that it needs "Off", "Learning", and
     "Validating" modes.  Wouldn't one state machine per interface be
     sufficient?  Why do you need the RA-Guard-level state machine in
     addition.

     (Of course, having only the interface-level state machines
     wouldn't prevent an implementation from providing a user
     interface that lets the administrator toggle the mode
     simultaneously for all interfaces on the RA Guard device.  This
     would allow the administrator to switch all interfaces to
     Learning mode, e.g., with a single mouse click.)

(2)  And one editorial comment:  In section 3.2., "RA-Guard state:
     LEARNING", you say:

     "A device or interface in the RA-Guard "Learning" state is
     actively acquiring information about the devices connected to its
     interfaces. The learning process takes place over a pre-defined
     period of time by capturing router advertisments or it can be
     event triggered. The information gathered is compared against
     pre-defined criteria which qualify the validity of the RAs."

     Can you elaborate on what "pre-defined criteria" means in the
     last sentence?

Best regards,
- Christian