TWC (AS11351) blocking all NTP?

Jared Mauch jared at
Mon Feb 3 20:46:50 UTC 2014

On Feb 3, 2014, at 3:29 PM, John R. Levine <johnl at> wrote:

>>> It seems thata hosts sending large amounts of NTP traffic over the
>>> public Internet can be safely filtered if you don't already know that
>>> it's one of the handful that's in the pools or another well
>>> known NTP master.
>> Speaking as one of the 3841 servers in the pool, I'm happy to be described as a "handful," something my mother used to say, but I do feel obligated to point out that it's a pretty big handful especially if you want to be fiddling ACLs on an hourly basis which is pretty much what it takes.
> I was thinking that the servers on any particular network are a small set of exceptions to a general rule to rate limit outgoing NTP traffic. allows any NTP operator to opt-in to receive NTP traffic should their clock be available and accurate.

- Jared

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