[time] Fwd: [time-dev] NTP survey

Ryan Malayter ryan
Mon Feb 8 17:40:58 UTC 2010

On Mon, Feb 8, 2010 at 8:16 AM, Ishan Vaishnavi <I.Vaishnavi at cwi.nl> wrote:
> Any pointers, helpful suggestion, articles are welcome.

I would make a suggestion for your survey, and that would be not to
rely soley on "walking the tree" of known ntp associations as previous
surveys have done. GPS is now cheap, and there are a lot more
"disconnected" NTP hierarchies out there than there were previously.
Also, I would suspect there are a lot more systems which are
configured to not respond to NTP management packets (as that is now
the default configuration in many NTP distributions).

So I think that leaves random scanning for NTP servers. Of course,
randomly knocking on UDP port 123 is considered somewhat rude, and
would look a lot like a machine infected with a virus/trojan/rootkit
to your ISP. I would think you would need some coordination with your
provider, and having reverse DNS and informational web pages as was
done in previous surveys would be a necessity.

However, by random scanning, you can get a pretty decent statistical
estimate about the total state of NTP on the Internet that might not
be achiveable with other methods that relied upon a "seed list" of NTP


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