At 11:26 PM -0700 2005-09-11, Nelson Minar wrote:
Hey, that's a good idea. ntpd is already figuring out which clocks are
best from a big list; just give it a big list from pool.ntp.org and
let it figure out which one is closest / best time. The only drawback
I see here is that if we recommend this as a default, the traffic from
each client goes up a lot. Maybe there's a way to get the servers
implementation to choose just 3-4 servers after a few hours?
In the Reference Implementation, there are "tos minclock" as well
as "tos minsane" parameters, which Dr. Mills has said that he wishes
he could have each default to four, because he's learned lessons
since the defaults were set in the code. However, he fears that this
would hurt way too many sites that stupidly depend on those defaults
being what they are.
I imagine there's probably already a "tos maxclock" directive,
and it shouldn't be too hard to add one if there's not already.
Certainly, there is an effective "tos maxclock" setting of ten, in
the current code. With well-behaved clients, monitoring ten upstream
time servers should not cause excessive load on those servers.
I think the lowest reasonable default value you could specify for
"tos maxclock" would be five, so that you can detect and eliminate
two falsetickers, and that would only cut the traffic to the servers
by half. If there are enough servers defined, and the load-balancing
is done right, this should not be a significant impact on the servers
in question. IMO, today the DNS-based load-balancing is not done
right, but I think that Ask probably already has the tools in hand to
address this issue.
No, I think the real problem is going to be abusive clients.
However, I think there is another risk here -- if we try to do
too much with the pool, I fear that many people are going to use it
as a way to try to squeeze out the last nanosecond of accuracy for
their clocks, and that will definitely cause excessive traffic to the
servers. IMO, it's better to target providing less services of a
more moderate quality, and encourage those people who want to tweak
their clock performance to the last nanosecond to use the pool as
only one input.
--
Brad Knowles, <[EMAIL PROTECTED]>
"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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