[ntpwg] [dhcwg] NTP option for DHCPv6 [draft-gayraud-dhcpv6-ntp-opt-01.txt] posted

[Danny Mayer]

Richard Gayraud (rgayraud) wrote:
> Hello Danny,
> 
> Thank you very much for your comments. Please see inline our reply.
> 
> Regards, 
> Richard.
> 
> Danny Mayer (mayer at ntp.isc.org) wrote:
>> Well my first question is why are you calling out NTPv4? Will 
>> it break if it's v5? If so it's flawed. If not that should be 
>> removed.
> 
> I think you are right. Do you think we should call out for "NTPv4 
> or higher version", or simply "NTP" ? Given that this is running 
> only on IPv6, so by definition, only for NTP >= 4 ?
> 

True enough. NTPv3 did not officially support IPv6 though that was not 
the reason for the major version change. I think NTP is sufficient.

>> Second, how does this differ from the SNTP options in 
>> RFC4075? Is there a reason that you know of that requires 
>> that they be separate options? I can see no reason for both.
>>
>> Danny
> 
> This differs from SNTP options by various things. One is the FQDN
> capability. Another one is the use of sub-options that will enable
> easier extendability.
> 

None of that really matters since you use whichever pieces you want to 
use at the receiving end.

> But, the main point is the fact that RFC4075 advertise SNTP servers,
> which are, by definition stratum-1 servers. This is not suitable
> for the common case of client workstations on a LAN. Doing so would 
> imply that these LANs would all have a local stratum-1 server.
> 

That's a misconception on the part of the authors of RFC4075. The 
current SNTP RFC 4330 talks about SNTP Servers being required to be 
Stratum 1 servers but says nothing about SNTP clients needing to use 
them. RFC 4075 and this draft is about the clients rather than the 
servers. An SNTP Client can use any SNTP server or NTP server of any 
stratum without limits (except for policy limits). Furthermore there is 
no difference in the on-the-wire packets of an SNTP client or server 
from a NTP client or server. The stratum of the client becomes one 
greater than the stratum of the server chosen by the NTP algorithms.

Please also see the latest NTP v4 draft just published: 
http://www.ietf.org/internet-drafts/draft-ietf-ntp-ntpv4-proto-09.txt

> This looks like a mistake in 4075, both in wording and intend. One
> may want to deprecate 4075, but some people said at the last IETF 
> that it could be of some use if someone wants to advertise SNTP 
> stratum-1 servers via DHCP.

I recommend deprecating RFC 4075 and replacing it with this one and 
reusing the option numbers and updating the IANA registrations of those 
options to include NTP.

I hope this clarifies matters.

Danny