Re: [babel] info-model: calculated and received metrics

["STARK, BARBARA H" <[e-mail]>]

> > For a route to exist in the info model babel-routes object, either the
> > received or calculated metric MUST be non-zero (rfc6126bis only
> > mentions the received metric as being in its route table).
> 
> Zero is a perfectly fine value for a metric (actually, the very best).
> Perhaps you meant defined instead of non-zero?

I don't think I got the descriptions for calculated and received metrics right, given Juliusz statement that 0 is the best possible metric. What I'm struggling with, is what value is assigned to these parameters when they aren't received (for the received metric) or calculated (for the calculated metric)? Should they be "null"? Wouldn't that be a problem in systems/languages that don't distinguish between 0 and null for integer types? Or are there no such languages/systems?

Here are the descriptions in the current draft:

   babel-route-received-metric:  The metric with which this route was
      advertised by the neighbor, or maximum value to indicate the route
      was recently retracted and is temporarily unreachable (see
      Section 3.5.5 of [I-D.ietf-babel-rfc6126bis]).  This metric will
      be 0 (zero) if the route was not received from a neighbor but was
      generated through other means.  At least one of babel-route-
      calculated-metric and babel-route-received-metric MUST be non-
      zero.  Having both be non-zero is expected for a route that is
      received and subsequently advertised.  This is a 16-bit unsigned
      integer.

   babel-route-calculated-metric:  A calculated metric for this route.
      How the metric is calculated is implementation-specific.  Maximum
      value indicates the route was recently retracted and is
      temporarily unreachable (see Section 3.5.5 of
      [I-D.ietf-babel-rfc6126bis]).  At least one of babel-route-
      calculated-metric and babel-route-received-metric MUST be non-
      zero.  Having both be non-zero is expected for a route that is
      received and subsequently advertised.  This is a 16-bit unsigned
      integer.

Barbara