NIST IPv6 document

Fri Jan 7 02:13:52 UTC 2011

On Thu, Jan 6, 2011 at 8:47 PM, Owen DeLong <owen at delong.com> wrote:
> 1.      Block packets destined for your point-to-point links at your
>        borders. There's no legitimate reason someone should be

Most networks do not do this today.  Whether or not that is wise is
questionable, but I don't think those networks want NDP to be the
reason they choose to make this change.

> 2.      For networks that aren't intended to receive inbound requests
>        from the outside, limit such requests to the live hosts that
>        exist on those networks with a stateful firewall.

Again, this doesn't fix the problem of misconfigured hosts on the LAN.
 I can and shall say it over and over, as long as folks continue to
miss the potential for one compromised machine to disable the entire
LAN, and in many cases, the entire router.  It is bad that NDP table
overflow can be triggered externally, but even if you solve that
problem (which again does not require a stateful firewall, why do you
keep saying this?) you still haven't made sure one host machine can't
disable the LAN/router.

> 3.      Police the ND issue rate on the router. Yes, it means that
>        an ND attack could prevent some legitimate ND requests
>        from getting through, but, at least it prevents ND overflow and
>        the working hosts with existing ND entries continue to function.
>        In most cases, this will be virtually all of the active hosts on
>        the network.

You must understand that policing will not stop the NDCache from
becoming full almost instantly under an attack.  Since the largest
existing routers have about 100k entries at most, an attack can fill
that up in *one second.*

On some platforms, existing entries must be periodically refreshed by
actual ARP/NDP exchange.  If they are not refreshed, the entries go
away, and traffic stops flowing.  This is extremely bad because it can
break even hosts with constant traffic flows, such as a server or
infrastructure link to a neighboring router.  Depending on the attack
PPS and policer configuration, such hosts may remain broken for the
duration of the attack.

Implementations differ greatly in this regard.  All of them break
under an attack.  Every single current implementation breaks in some
fashion.  It's just a question of how bad.

-- 
Jeff S Wheeler <jsw at inconcepts.biz>
Sr Network Operator  /  Innovative Network Concepts