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

[Danny Mayer <[e-mail]>]

Brian Utterback wrote:
> Danny Mayer wrote:
>
>> There is *no* avantage to not sending a FQDN and plenty of
>> disadvantages to not doing so. Would you like a list of vendors who
>> have hardcoded IP addresses into their devices without permission
>> of the operator of that NTP server causing headaches for not just
>> the owner of the NTP Server but also for the users of those
>> devices? The NTP reference implementation expects the existence of
>> a resolver so you haven't gained anything.
>>
>
> As already noted, there is an advantage, namely that the client does
> not have to have a resolver. And even if the reference implementation
>  requires one (Is that really true? Even if no name resolution is
> required?) DHCP should remain implementation agnostic.
>

The reference implementation calls getaddrinfo(). Whether it actually
contacts a resolver depends partly on the O/S.

> As far the "hard coded address" problem goes, I don't see that
> scenario as very likely. DHCP clients don't tend to remain up for
> very long periods. And you don't have the same IP addresses being
> served by thousands of DHCP servers. The thing to be careful of is
> that the DHCP server not be embedded and replicated with hard coded
> addresses, not that the clients only get IP addresses.

This laptop that I'm typing on hasn't been restarted in at least a
month. The NTP server (which I am stopping and starting constantly as
I'm testing and debugging code) would not normally be stopped and never
fetches an new addresses once it has them. In the meantime it's changing
networks at least 3 times a day and therefore getting a new address from
DHCP each time. Currently, if the DHCP server were to send me new IP
addresses for the NTP server it would ignore it as it's already running
and doesn't look at anything before it's restarted or you use ntpdc to
change it. So except for bootup, sending me IP addresses every time I
change my local IP address would be useless since the running ntpd
server doesn't get notified, at least not right now.

If you want to use the DHCP server essentially as a resolver (it looks
up the addresses and sends them to the NTP server) that's fine except
there's no mechanism currently in place to do that.

Danny

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