[Ntp] Antw: Re: draft-ietf-ntp-mode-6-cmds : Issue 1

>>> Harlan Stenn <stenn@nwtime.org> schrieb am 19.09.2017 um 01:36 in Nachricht
<ad816de0-b31e-2b06-a628-28fc32d9a2f1@nwtime.org>:

> 
> On 9/18/2017 10:10 AM, Brian Haberman wrote:
>> Ulrich noted that this document does not specify a version number for
>> the mode 6 commands. I had suggested specifying it as "version 4 (or
>> earlier)" given that the introduction of mode 6 commands has occurred at
>> various versions of the protocol starting at RFC 1305. Ulrich pointed
>> out that the version number drives the interpretation of the status words.
>> 
>> For people who have implemented or use mode 6 commands, what makes sense
>> here? Do we need to specify a version number per mode 6 command?
> 
> I've long wanted a way to identify more information about information
> about what information is available via mode6 commands, and the format
> of that information.
> 
> While some of this information is part of the "core", a lot of it is
> implementation-specific, and can easily change from one code version to
> the next.

Hi!

"It can", but should it? If you are writing software for yourself, you are free to change it all the time. But if you implement some standard, either stick to the standard, or define a new standard. Arguing that this part is not in the standard does not help anyone. As a matter of fact NTPv3 and NTPv4 return different information for the exactly same command. Obviously that was an oversight when changing things, but that should not repeat, and, if possible, also clean up the past (i.e.: provide a mechanism to get well-specified responses).

> 
> I don't think we want to cast any of this into concrete.

This kind of flexibility on your side causes confusion on the other side.
Let me quote some of my Perl code again (trying to get version independent NTP performance gauges):

        if (!$NTPv4) {
            $vars->set_variable('frequency', $vars->variable('freq') / 1000);
            $vars->set_variable('offset', $vars->variable('phase'));
            $vars->set_variable('noise', $vars->variable('error'));
            $vars->set_variable('jitter', 0);
            $vars->set_variable('stability', '0');
        } else {            # ntpd 4.2.6p2 "introduces" "new" variables
            $vars->copy_variable('rootdispersion', 'rootdisp');
            $vars->copy_variable('noise', 'clk_jitter');
            $vars->copy_variable('jitter', 'sys_jitter');
            $vars->copy_variable('stability', 'clk_wander');
            $vars->copy_variable('poll', 'tc');
            # ntpd 4.2.8 also has new variables
            # "clk_jitter" (CS_ERROR),
            # "ctr_frequency" (Windows: Performance Counter Drift)
        }

So it's hard to get one set of well-defined variables. Don't make it worse!

> 
> On the other hand, we do need a way to figure out what's available
> (which may changed based on authorization levels) and the format in
> which it's presented.

Absolutely!

Regards,
Ulrich

> 
> -- 
> Harlan Stenn, Network Time Foundation
> http://nwtime.org - be a Member!
> 
> _______________________________________________
> ntp mailing list
> ntp@ietf.org 
> https://www.ietf.org/mailman/listinfo/ntp 