Filter NTP traffic by packet size?

Nick Hilliard nick at
Sat Feb 22 15:06:32 UTC 2014

On 22/02/2014 09:07, Cb B wrote:
> Summary IETF response:  The problem i described is already solved by
> bcp38, nothing to see here, carry on with UDP

udp is here to stay.  Denying this is no more useful than trying to push
the tide back with a teaspoon.

It's worth bearing in mind that any open tcp service will send out several
acks before giving up.  In other words, any standard open tcp socket will
provide a level of amplification worth using even if UDP were to be
switched off tomorrow.  Sure, not as good as the 230x amplification that
ntp monlist will give, but it's still a problem.

In the long term, it would be more useful to spent time and effort building
automated tools to track down the sources of the spoofed packets than
trying to deprecate UDP.


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