5.3-R: /etc/ntp.conf doesn't exist
brad at stop.mail-abuse.org
Wed Nov 10 03:47:08 PST 2004
At 8:45 PM -0800 2004-11-09, Brooks Davis wrote:
> At a glance these guidelines seem reasionable, but it doesn't appears
> that having 4-5 upstreams and having a file that just works are
If you want to protect yourself against at least one falseticker,
you have no choice but to use at least four upstream time servers.
Brian Utterback can explain the math better than I can, but that's
the simple facts of the matter.
> So long as we're not at risk of swamping a server like one
> of the AP vendors did, having something that just works is going to
> trump following the recommendations exactly. It's not clear to me that
> you can do both at the moment. IMO, it's really lame to say that you
> should use at least 5 servers and then only provide a stable way to
> access 3 of them. If 5 is the recomendation, there should be
> 3.pool.ntp.org and 4.pool.ntp.org entries.
I wrote most of the TWiki entry that you read, based on comments
I got from a variety of people, including fellow contributors to
ntp.org/ntp.isc.org and knowledgeable participants on the
Adrian runs the pool.ntp.org stuff as a separate project, and
I've been trying to get him and the other members of the
timekeepers at fortytwo.ch mailing list to contribute content to the
TWiki, or to just give me feedback that I can use, but I have not yet
been able to get any of them to do so.
Most of the public support stuff has been moved from ntp.org over
to ntp.isc.org (bugzilla is the last thing to be moved over), but
even before that, Adrian's project was pretty much a completely
separate effort and the only thing it shared with anything that the
rest of us were doing was the ntp.org domain name.
It used to be something totally different under Adrian's own
domain name, but Dr. Mills liked the idea well enough that he worked
with UDel to get pool.ntp.org delegated to Adrian's machines, so that
he could run that part of his project totally separate from
everything else, and largely without interference or interaction with
Note that many of the servers in the pool are on ADSL or other
low-bandwidth personal lines, do not have great clocks, running older
NTP server code or alternative server code which might cause problems
for people running a modern ntpd, and the monitoring system right now
also has some problems. For example, the recent issue that caused
all of pool.ntp.org to become empty since the monitoring system was
offline and it thought that all of the servers were offline, so it
dutifully removed them all from the respective zones.
My understanding is that the concept for pool.ntp.org was to
provide decent-enough additional time sources in most cases for the
majority of people using the system, without necessarily any regard
for locality of reference (if you're using the top-level pool.ntp.org
zones, those servers could be anywhere in the world), and definitely
without being the primary source of time for most people.
If you are a customer of a local ISP that has one or two time
servers that they provide for your use, then using your
country-code/regional pool.ntp.org zone is a perfect way to fill in
the extra slots that you want/need to get up to the minimum level you
should have in order to protect yourself against falsetickers. If
your country-code or regional sub-zone doesn't have enough servers in
it, then you can always take one step higher.
Providing the .whatever.pool.ntp.org zones is a hack to get
around problems that some people have with broken resolvers which
don't implement round-robin correctly, and prevent configurations
from working where you list the exact same "server pool.ntp.org" line
multiple times in your /etc/ntp.conf. But it's just a hack.
Do keep in mind that some server operators in pool.ntp.org are
already complaining about individual ill-behaved clients that are
hitting them once or twice a second, and firewalling them off.
Then there was the recent incident when a small, heretofore
unknown, provider of network equipment from the UK decided to ship
out an update to their platform and pretty much got the entire
pool.ntp.org server operator community in an uproar due to excessive
traffic. It took a few days to find out who the provider was, then a
few more days to convince them to fix their software, and then it
took a few more days for the rollout to occur and to get most of
their small customer base fixed.
If you're interested in reading more about this topic, go to the
archives of Adrian's timekeepers mailing list and search for things
like "netpilot", "Guidelines for large scale use", and "excessive
In the meanwhile, I've been trying to do what I can to help
various projects get their own NTP configurations into more
reasonable shape, based on what is currently in the TWiki.
> If you have specific recomendations to fix the file, please make them.
At the very least, if you're going to put .pool.ntp.org in
your default /etc/ntp.conf file, you certainly couldn't hurt yourself
any worse by also including northamerica.pool.ntp.org,
europe.pool.ntp.org, and asia.pool.ntp.org, since all of the servers
listed in the lower level pools also get listed in the higher level
pools, and you can be reasonably certain that you're already going to
get a world-wide distribution of servers within the
.pool.ntp.org lists no matter what.
Assuming no broken resolvers, and given the total number of
servers currently listed in the pool, there should be relatively
little chance of collision between the .pool.ntp.org and the
<region>.pool.ntp.org zones, and you should result in getting five or
six distinct IP addresses for ntpd to use.
> Perhaps ntp.org should provide such a file.
I'm not convinced that we can provide such a file. Each
different platform is going to have their own ideas of where log data
should be sent, where statistics files should be kept, etc.... What
might work for FreeBSD might not work for NetBSD and certainly
wouldn't work for OpenBSD, and Linux would be a totally different
Then there are the other 20+ platforms that we support, including
non-*nix related OSes as Microsoft Windows NT/2000 and VMS; embedded
platforms like QNX and VxWorx; ancient versions of Unix such as
Ultrix, DomainOS, and SunOS 4; as well as a wide variety of "modern"
Unix and Unix-like OSes.
If we were to provide a standard default configuration file that
was required to work equally across all platforms, it would have to
be stripped of all features other than specifying a set of at least
four servers to be used.
Certainly, we can provide information and advice to the relevant
projects and the people doing NTP-related work on those projects, and
we are interested in doing whatever we can to help get everyone to an
equally high level of performance, quality, and robustness of
But I have to believe that there's going to be some
project-specific parts to those configurations files, and we can't
specify or dictate what they should be -- nor do I believe that we
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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