Andy Smith wrote:
Hi Rob,
On Sun, Feb 19, 2017 at 06:49:38PM +0100, Rob Janssen wrote:
That way the customers of some ISP could be directed to the
timeservers provided by that ISP, and similar for other networks
that have good timeservers and a DNS resolver.
How would you distinguish ISPs with "good timeservers" from ones
with unreliable timeservers, where I (as a customer of that ISP)
will specifically want to avoid their servers and prefer the pool
only?
Well, as I already mentioned, it could be configured in such a way that the
servers
are polled the same way as any pool server, and taken out of the list when they
are
not within tolerances, just like any other server.
What is different is that those servers do not have to be in the pool for
outside
users, and they are heavily biased when requested by users inside the network.
If I know enough to configure an NTP client then I am going to
select pool servers and my ISP's servers, knowing that NTP's
selection algorithm should rescue me if my ISP's servers go bad. I
do not then want the pool to bias towards my ISP's servers.
This solution is intended for the problem that certain modem/router
manufacturers
pre-configure their equipment with NTP servers like "europe.ntp.pool.org"
(AVM/Fritzbox)
or "ntp.pool.org" (many others). The vast majority of users never changes
that, and
those routers (hundreds of thousands of them) all poll the NTP pool servers,
even
when the ISP has their own local servers that they choose not to put in the
pool.
(e.g. my provider XS4ALL)
If an ISP was concerned about NTP traffic leaving their network
then they could provide their own NTP servers. Assuming they end up
performing better than the average pool server -- which they should as
there's going to be a lot less latency to their own customers than
between rest of Internet and own customers -- then more of the
traffic should stay on-net.
That is what they do. But they cannot enforce their clients to use those
servers, and
such a change to the pool DNS would allow them to do so.
(without dirty hacks like making europe.pool.ntp.org return the addresses of
their servers
through the configuration of their DNS resolvers)
Rob
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