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

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

I've heard no response to this question. I've confirmed that in TR-181 I do have a problem (a uint with value of 0 or NULL will be transmitted in a TR-181 data model as 0), because it defines "NULL" as:
------------- excerpt from TR-106 Data Model Template --------------------
Each primitive data type has an associated null value that is used, for example, as the expansion of the {{null}} template (A.2.2.4). These null values are defined as follows:
* base64, hexBinary, string: an empty string
* unsignedInt, unsignedLong: 0
* int, long: -1
* boolean: false
* dateTime: 0001-01-01T00:00:00Z (the Unknown Time; see Section 3.2.1)
A null reference indicates that a reference parameter is not currently referencing anything. The value that indicates a null reference is the null value for the reference parameter's base data type, i.e.:
* string: an empty string
* unsignedInt: 0
* int:
-------------------------
But since the problem is just in the reporting and not in the Babel implementation's use of the values, maybe I should just mention that users should be careful when interpreting 0, since it can mean the value was not received / calculated?

What I could do is something like:

   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 NULL if the route was not received from a neighbor.  At least one of babel-route-
      calculated-metric and babel-route-received-metric MUST be non-
      NULL.  Having both be non-NULL is expected for a route that is
      received and subsequently advertised.  This is a 16-bit unsigned
      integer. Some data models may be unable to distinguish between 0 (zero)
      and NULL for unsigned integers, which will cause NULL values to be
      reported as 0.

   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-
      NULL.  Having both be non-NULL is expected for a route that is
      received and subsequently advertised.  This is a 16-bit unsigned
      integer. Some data models may be unable to distinguish between 0 (zero)
      and NULL for unsigned integers, which will cause NULL values to be
      reported as 0.

Barbara

> > > 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
> 
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