TWC (AS11351) blocking all NTP?

John Kristoff jtk at
Mon Feb 3 22:21:34 UTC 2014

On Mon, 03 Feb 2014 16:49:37 +1300
Geraint Jones <geraint at> wrote:

> We block all outbound UDP for our ~200,000 Users for this very reason
> (with the exception of some whitelisted NTP and DNS servers). So far
> we have had 0 complaints

I've heard this sort of absence of complaint statement used to justify
some sort of truth claim about how to operate a network a number of
times before.  There is a certain appeal to it, particularly in cases
such as this and for certain types of networks and operators, but if
nothing else, for those that do it, I would also like to see some
additional analysis about what is being filtered.  It leaves many
unconvinced and left to conjecture what the right approach is otherwise.

If you have done that analysis or if you could make available some of
that data for a research project, it would be very helpful for
everyone to see what the measurable effect is.  It would also make
for a useful research project.


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