TWC (AS11351) blocking all NTP?

Dobbins, Roland rdobbins at
Mon Feb 3 07:08:25 UTC 2014

On Feb 3, 2014, at 1:54 PM, Michael DeMan <nanog at> wrote:

> I certainly would not want to provide as part the AUP (as seller or buyer), a policy that fundamentals like NTP are 'blocked' to customers.  Seems like too much of a slippery slope for my taste.

The idea is to block traffic to misconfigured ntpds on broadband customer access networks, not to limit their choice of which ntp servers to use.

> In regards to anti-spoofing measures - I think there a couple of vectors about the latest NTP attack where more rigorous client-side anti-spoofing could help but will not solve it overall.

Rigorous antispoofing would solve the problem of all reflection/amplification DDoS attacks.  My hunch is that most spoofed traffic involved in these attacks actually emanates from compromised/abused servers on IDC networks (including so-called 'bulletproof' miscreant-friendly networks), but I've no data to support that, yet.

>  Trying to be fair and practical (from my perspective) - it is a lot easier and quicker to patch/workaround IPv4 problems and address proper solutions via IPv6 and associated RFCs?

There's nothing in IPv6 which makes any difference.  The ultimate solution is antispoofing at the customer edge.

Roland Dobbins <rdobbins at> // <>

	  Luck is the residue of opportunity and design.

		       -- John Milton

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