[ntpwg] [dhcwg] Re: Network Time Protocol (NTP) Options for DHCPv6

[Brad Knowles]

On 11/26/07, Mark Stapp wrote:

>  I do wonder why some folks seem to think that using DNS names would
>  somehow be "safer" than using v6 addresses. if someone shipped a server
>  with a canned list of DNS names for NTP servers, there would be a
>  problem until the owners of the NTP servers named moved them. I don't
>  see how that'd be any better than the analogous mistake involving IP
>  addresses.

If the name was "pool.ntp.org", today that load would be spread over 
more than 1500 hosts around the world, and we hope that there will be 
many more participants in the pool in the future.  Moreover, Ask 
Bjorn Hansen has apparently done a fairly good job of building a 
robust load-balancing nameserver architecture for this system, and so 
far as I know would be able to handle a UWisc or PHK-scale disaster 
plus the "normal" load.

Now, 1500 versus millions of misconfigured clients, that's not such a 
great bet.  But it's orders of magnitude better than just a single IP 
address.

>  aside from the catastrophe hypothetical, is there any really strong
>  reason - anything to do with the NTP protocol - that would prevent the
>  use of ipv6 addresses?

At the technical level, no.  IP addresses (of both forms) and names 
should have no technical difference.  Of course, this assumes that if 
you're handing out IPv6 addresses that you'll have full IPv6 stacks 
on both sides and a fully IPv6-compatible network underneath, and if 
you hand out IPv4 addresses that you're connected to the appropriate 
IPv4 network (and not isolated on some IPv6-only island), but that's 
a different matter.

At the practical operations level, yes.  See above.

-- 
Brad Knowles <brad at shub-internet.org>
LinkedIn Profile: <http://tinyurl.com/y8kpxu>