Re: [ippm] AD review: draft-ietf-ippm-storetraceroutes-03

[Henk Uijterwaal <henk at ripe.net>]

Lars, others,

> > > > Section 5.2., paragraph 0:
> > > > > 5.2.  Information Elements
> > > >
> > > >   Does it make sense to have default values for the information 
> > > > elements
> > > >   at all? I mean, the data captured by the information model is the
> > > >   result of a particular traceroute measurement, which will have been
> > > >   taken with a fully specified set of parameters. So the defaults will
> > > >   never be actually used, no?
> >
> > I'd personally prefer sensible defaults for values over "undefined" or
> > "NaN" when creating a new instance of a measurement.  That way, I don't
> > have to remember that my code should change the values.  YMMV, but I
> > don't think it hurts to have them.
>
> If the information model captures parameters and results of a traceroute 
> measurement, there should never be any undefined or unknown parameters. 
> Even if the traceroute measurement used some default parameters of a 
> specific traceroute *implementation*, the information model should 
> contain the actual parameters used.  Different tracerotue 
> implementations have different defaults, so I don't see how the 
> information model can have any defaults that are valid for all 
> implementations.

There are a couple of things where (at least all implementations that
I've seen) traceroute uses whatever the operating system returns.  The
default G/W is one example, if one runs traceroute on a box with two
connections, it will pick whatever the O/S picks when the program is
run.  There are more and for lots of measurements, this will be good
enough.

I agree that it should be clear from the data that the user didn't set
this parameter.  So, how about setting all elements by default to
something that is clearly "impossible"?

Henk

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Henk Uijterwaal                           Email: henk.uijterwaal(at)ripe.net
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