Rate of growth on IPv6 not fast enough?

Owen DeLong owen at delong.com
Tue Apr 20 14:59:32 CDT 2010

On Apr 20, 2010, at 12:31 PM, Roger Marquis wrote:

> Jack Bates wrote:
>> .01%? heh. NAT can break xbox, ps3, certain pc games, screw with various
>> programs that dislike multiple connections from a single IP, and the
>> crap load of vpn clients that appear on the network and do not support
>> nat traversal (either doesn't support it, or big corp A refuses to
>> enable it).
> If this were really an issue I'd expect my nieces and nephews, all of whom are big
> game players, would have mentioned it.  They haven't though, despite being behind
> cheap NATing CPE from D-Link and Netgear.
> Address conservation aside, the main selling point of NAT is its filtering of inbound
> session requests.  NAT _always_ fails-closed by forcing inbound connections to pass
> validation by stateful inspection.  Without this you'd have to depend on less

Repeating the same falsehood does not make it any less false.

> reliable (fail-open) mechanisms and streams could be initiated from the Internet at
> large.  In theory you could enforce fail-closed reliably without NAT, but the rules

Stateful Inspection can be implemented fail-closed. I point to Juniper ScreenOS
and Services JunOS as examples of this.  Absent a specific permit or specific
configuration telling it to pass particular traffic inbound, traffic must pass the same
stateful inspection that NAT would require.  This is default behavior in those boxes.
The rules are not complex at all.

> would have to be more complex and complexity is the enemy of security.  Worse, if
> non-NATed CPE didn't do adequate session validation, inspection, and tracking, as

Again, you simply are not correct here. I'm not sure what level of implementation is
available in low-end gear as it hasn't met my needs in a long long time.  However,
I will say that although an SRX-100 is not especially low-end at 10x absolute low
end pricing and 5x average home gateway pricing, it is low-enough end that I
know this can be done in reasonable gear.

> low-end gear might be expected to cut corners on, end-user networks would be more
> exposed to nefarious outside-initiated streams.
Frankly, even with NAT, corner-cutting in those areas can lead to things passing which
you don't expect.

> Arguments against NAT uniformly fail to give credit to these security considerations,

Because they are false.  It's not that they fail to give credit to them. It's that they know
them to be false. It's like saying that discussions of breathing gas fail to give credit
to the respiratory effects of the trace amounts of argon present in the atmosphere.

> which is a large reason the market has not taken IPv6 seriously to-date.  Even in big
> business, CISOs are able to shoot-down netops recommendations for 1:1 address mapping
> with ease (not that vocal NAT opponents get jobs where internal security is a
> concern).
While I recognize that there is a group of people who religiously believe that NAT
has a security benefit, I don't think the represent a significant fraction of the reasons
IPv6 is not getting deployed. Frankly, many of them have more IPv6 deployed than
they realize and their NAT is not protecting them from it at all. It may even be helping
some of the nefarious traffic that may be taking advantage of the current situation
to remain safely anonymized and invisible.


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