[ntp:questions] Bad NTP servers jeopardizing the pool.ntp.org initiative
mayer at ntp.isc.org
Mon Apr 2 03:14:37 UTC 2007
Harlan Stenn wrote:
>>>> In article <460FAE61.40804 at ntp.isc.org>, mayer at ntp.isc.org (Danny Mayer) writes:
> P> As you might have seen elsewhere I do agree that this is only a good
> P> idea under well defined circumstances, and I would now add that it is
> P> difficult to ascertain up-front whether these conditions are met (i.e.
> P> whether it would be desirable for a particular NTP server on a dynamic IP
> P> address to be admitted to the pool).
> Danny> There are *no* circumstances where this is a good idea. You *cannot*
> Danny> make use of a server that is constantly moving IP address. Even fixed
> Danny> IP addresses can be problematic in this environment since the clients
> Danny> don't requery for addresses after they come up and if someone decides
> Danny> to move the server elsewhere, they will never know about it.
> Danny, while you are right that one cannot expect to get useful NTP service
> from a moving IP address you are flat out wrong that all DHCP-assigned
> addresses fall in to this category.
To clarify one thing, an IP address that is fixed for a given server is
fixed even if it's assigned by DHCP. How it gets assigned is a detail.
Whether or not that server keeps the same address is crucial.
> I think you have tunnel-vision in this case, and are being blind to some
> cases where obvious/known counter-examples exist.
I don't think so. Please provide counter-examples.
> P> Please remember that I started this suggestion in the context of a
> P> discussion of code being added to ntpd that re-resolves server addresses
> P> in case of non-reachability. Such code, _if deployed on a critical mass
> P> of clients_ (i.e. optimistically, not for a good few years) would address
> P> your concern (while not completely removing it).
> Danny> We are not the only provider of NTP Clients or for that matter
> Danny> servers and unless they also make changes to also do this and have
> Danny> everyone upgrade the problem will remain. For most people/admins this
> Danny> is a set and forget item when they set up a system.
> Danny, from my POV you didn't even address Per's point, and his point seems
> perfectly valid to me.
Which point would that be? Having NTP servers with varying addresses is
a good idea? Even when the above mentioned code change happens, and that
will take quite a lot of work and will cause me to make a lot of changes
to the code and even longer to get it just right, it still won't deal
with the issues I've raised including the fact that there are a lot of
other NTP clients out there. We already have cases of people hardcoding
IP addresses of NTP servers without unauthorization of the owner of the
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