TWC (AS11351) blocking all NTP?

Cb B cb.list6 at
Sun Feb 2 23:09:55 UTC 2014

On Feb 2, 2014 2:54 PM, "Matthew Petach" <mpetach at> wrote:
> On Sun, Feb 2, 2014 at 2:17 PM, Cb B <cb.list6 at> wrote:
> > On Feb 2, 2014 8:35 AM, "Jonathan Towne" <jtowne at> wrote:
> > >
> > > The provider has kindly acknowledged that there is an issue, and are
> > > working on a resolution.  Heads up, it may be more than just my
> > >
> >
> > And not just your provider, everyone is dealing with UDP amp attacks.
> >
> > These UDP based amp attacks are off the charts. Wholesale blocking of
> > traffic at the protocol level to mitigate 10s to 100s of gigs of ddos
> > traffic is not "knee jerk", it is the right thing to do in a world where
> > bcp 38 is far from universal and open dns servers, ntp, chargen, and
> > whatever udp 172 is run wild.
> >
> > People who run networks know what it takes to restore service. And
> > increasingly, that will be clamping ipv4 UDP in the plumbing,  both
> > reactively and proactively.
> >
> Please note that it's not that UDP is at fault here; it's
> applications that are structured to respond to small
> input packets with large responses.

I dont want to go into fault, there is plenty of that to go around.

> If NTP responded to a single query with a single
> equivalently sized response, its effectiveness as
> a DDoS attack would be zero; with zero amplification,
> the volume of attack traffic would be exactly equivalent
> to the volume of spoofed traffic the originator could
> send out in the first place.
> I agree the source obfuscation aspect of UDP can be
> annoying, from the spoofing perspective, but that
> really needs to be recognized to be separate from
> the volume amplification aspect, which is an application
> level issue, not a protocol level issue.

Source obfuscation is not annoying. Combined with amplification, it is the
perfect storm for shutting down networks... whereby the only solution is to
shutdown ipv4 udp. Or wave the magic wand that makes bcp38 universal,
patches boxes, and so on.

My point is: dont expect these abbused services on UDP to last. We have
experience in access networks on how to deal with abused protocols. Here is
one reference

My crystal ball says all of UDP will show up soon.


> Thanks!
> Matt
> PS--yes, I know it would completely change the
> dynamics of the internet as we know it today to
> shift to a 1:1 correspondence between input
> requests and output replies...but it *would*
> have a nice side effect of balancing out traffic
> ratios in many places, altering the settlement
> landscape in the process.  ;)

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