Rate of growth on IPv6 not fast enough?

Owen DeLong owen at delong.com
Tue Apr 20 23:27:14 CDT 2010

On Apr 20, 2010, at 6:34 PM, Karl Auer wrote:

> On Tue, 2010-04-20 at 12:59 -0700, Owen DeLong wrote:
>> On Apr 20, 2010, at 12:31 PM, Roger Marquis wrote:
>>> NAT _always_ fails-closed
>> Stateful Inspection can be implemented fail-closed.
> Not to take issue with either statement in particular, but I think there
> needs to be some consideration of what "fail" means.
I believe we are talking about the case where some engineer fat-fingers
a change and Roger's claim is that a stateful inspection without NAT
box will permit unintended traffic while a NAT box will not.

My claim is that the stateful inspection box can be implemented such
that it has an equally secure set of failure modes for fat-fingering to
a NAT+stateful inspection device.
> Reading through the security alerts from any vendor is a pretty sobering
> process - stuff fails open more often than you might expect.

> So I think we should be very cautious about saying that things "fail
> open" or "fail closed".
My point is not that they do or do not fail closed, but, that a well designed
SI firewall will fail with the exact same security risks as a NAT device.

> We should be especially cautious about it when the functionality we are
> interested in is really no more than a happy side effect of some other
> functionality. NAT's "security", to the extent that it exists at all, is
> a side effect of what it is intended to do, which is translate and map
> addresses.
IOW, All of NAT's security comes from the fact that it requires a state
table, like stateful inspection.


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