[ntp:questions] What exactly does "Maximum Distance Exceded" mean?

Danny Mayer mayer at ntp.org
Mon Mar 16 13:22:51 UTC 2009

Joe Gwinn wrote:
> Status code values fixed.
> At 10:47 PM -0400 3/15/09, Danny Mayer wrote:
>> Joseph Gwinn wrote:
>>>  Hmm.  OK, but I think that we've kind of run off the rails.  Let me
>>>  summarize:
>>>  1.  Sun Microsystems' current behavior is not the issue, as I'm loading
>>>  old software from an old CD onto old computer hardware, hardware that
>>>  cannot support a newer version of Solaris than v9.
>>>  One of these old Solaris boxes did work with NTPv3 running an even
>>> older
>>  > version of Solaris, with no 9514 codes, deepening the mystery.
>>  >
>> The trouble here is that those codes are *very likely* likely to have
>> changed between V3 and V4 since there was a large rewrite between the
>> two. That's why looking at the source code is necessary to get you the
>> help you need.
> As discussed in my other reply, mutating codes is a blunder.   It's a
> good news bad news thing.  The good news is that NTP has succeeded on an
> unimagined scale.  The bad news is that because of that scale, one must
> be *very* respectful of NTP's existing base, and it can be constraining.

You won't get any argument from us. However, Dave Mills is responsible
for these codes and we haven't been able to get him to agree to not
change the test code numbers and to use new ones if he needs more and
just not reuse the old ones. He has good reasons for changing the tests
but changing the meaning of the same code is harder to fathom. His view
is that these are internal tests but when you are trying to track down a
problem with your ntp daemon, it's important to know what they mean.

>>  > The fact that this obsolete system can most likely support NTPv4 is
>>>  worth investigation, though.
>>>  2.  I think that what's happening is that I'm doing something dumb, and
>>>  I bet that there is no real difference in how NTPv3 or NTPv4 would
>>> react
>>>  to this faux pas, whatever it turns out to be.  Nor is source code
>>>  research needed or requested.
>>>  3.  The original question was how to interpret a specific status code,
>>>  9514.  I read the explanation in the documentation, but became no wiser
>>>  for it.  Thus my question. 
>> Which is why you need to look at the source code. Documentation isn't
>> always clear or definitive but the source code will tell you.
> It simply cannot be required to read source code to get the definitions
> of status codes, even if the documentation has to give one definition
> per NTP version.  NTP is used on hundreds of millions of computers.  Are
> we expecting that every time someone gets an unexpected code they either
> have to read the source code, or pay someone to read it for them?  I'm
> sorry, but that cannot work.

I agree, but I'm not the person you need to persuade. In V4 the flash
codes are listed in libntp/statestr.c. I don't know about V3.

You may also be amused by this sync code:
	{ CTL_SST_TS_WRSTWTCH,	"sync_wristwatch" },


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