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

Joseph Gwinn joegwinn at comcast.net
Tue Mar 17 03:57:13 UTC 2009


In article <rZidnbLPV6C-nSLUnZ2dnUVZ_o-WnZ2d at giganews.com>,
 "Richard B. Gilbert" <rgilbert88 at comcast.net> wrote:

> Joseph Gwinn wrote:
> > In article <49BDC52B.20808 at ntp.org>, mayer at ntp.org (Danny Mayer) wrote:
> > 
> >> Joseph Gwinn wrote:
> >>
> >>>>> The FAQ has to be the place for such explanations.
> >>>> I'm not sure if this qualifies as an FAQ as I don't recall that it has 
> >>>> come up before.  FAQ stands for Frequently Asked Questions.
> >>> RAQ then?  Rarely Asked Questions
> >>>
> >>> Seriously, I can't believe that I'm the only person in history to be 
> >>> perplexed by these status codes, and those little three-word summaries 
> >>> are a bit telegraphic.
> >>>
> >>> Joe Gwinn
> >>>
> >> You aren't the only one. These questions have been asked before by a
> >> number of people. In fact I had to look at this at one point when I was
> >> getting these codes. Of course I just looked at the source code and
> >> never looked for documentation.
> > 
> > My fundamental point is that expecting a significant part of the NTP 
> > user base to read the code simply does not scale, for a host of reasons.
> > 
> >  
> >> I will tell you that this is a combination of bits so it's not just a
> >> number. Each bit represents a test code that failed so you have quite a
> >> bit to look at.
> > 
> > Just for curiosity, how many semicolons are there in the NTPv3 and NTPv4 
> > codebases?  My impression is that each is about 20,000 or 30,000, but I 
> > don't know why or where I got the number.
> > 
> > Joe Gwinn
> 
> I once did a "line count" of the entire NTP codebase.  70,000 lines!

Oof!  I had no idea it was that large.  There is the reason why, out of 
millions of users, very few will ever read the code.  Even 20,000 lines 
would stop most people.  It would take at least a year of study to 
become reasonably familiar with the code.  In the 1970s I did such 
things for a living, but no longer would I be able to spend that much 
time on any one thing.  

Hmm.  In the 1970s, I worked on an embedded realtime program consisting 
of ~60,000 lines of assembly code running on a midicomputer, a SEL 
32/85.  The big innovation was when we went to Fortran.

Joe Gwinn




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