Using BIND - was Re: [ntp:questions] Re: How long do I havetowaitfor sync?
brad at stop.mail-abuse.org
Sat Jun 4 16:20:43 UTC 2005
At 10:08 AM +0000 2005-06-04, David J Taylor wrote:
> Thie idea of configuring my own DNS server to talk directly to the root
> DNS servers for the Internet had not occured to me, just as one would not
> normally talk to a stratum one NTP server directly. [Is there anything to
> learn from this for the NTP guys?].
The reason this works for the DNS and not for NTP is that the
information you get back from the DNS is cached for long periods of
time, and all the root nameservers do is hand out referrals. They
have a relatively small zone of information regarding .com, .edu.
.gov, and all the country-code top-level-domains (ccTLDs), and that's
all they know. The real information is provided by the servers below
that level, and because of caching you almost never contact the root
Imagine if you were asking for information from the Stratum-1
time servers, and all they did was provide referrals to time servers
that are closer to you, but did not actually provide any answers
themselves. Of course, you would then contact these time servers
that are closer to you, and they might provide referrals to other
time servers that are even closer (and further down in the stratum
chain). Once you finally found the time servers which are closest to
you, you would never again go talk to any upstream time servers,
unless your machine was rebooted or you manually changed the
Under circumstances like this, the Stratum-1 time servers might
actually be able to hold up under the load of millions and billions
of machines around the 'net. The analogy doesn't quite completely
hold, but that's about the closest I can come.
Now, imagine that you could locate extra "copies" of the
Stratum-1 time servers all around the world, using routing tricks to
make the same IP address appear to be in fifty or more locations on
the Internet. The root nameservers do this today (f.root-servers.net
alone has more than fifty instances around the world), through a
technique called "anycast".
The closest you get with NTP is something called "manycast", but
which does also significantly reduce the load on the upstream time
> I've added the .invalid at the end of my address (although while writing
> this post rather than before writing, so it may not appear) to alleviate
> any excess load I may be causing.
It worked. Thanks!
Brad Knowles, <brad at stop.mail-abuse.org>
"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."
-- Benjamin Franklin (1706-1790), reply of the Pennsylvania
Assembly to the Governor, November 11, 1755
SAGE member since 1995. See <http://www.sage.org/> for more info.
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