Re: Index values of zero

["C. M. Heard" <heard@pobox.com>]

On Sun, 29 Dec 2002, Wijnen, Bert (Bert) wrote:

> Sofar, I have been pushing back on index values of zero.
> In principle I want MIB document authors/editors to 
> explain in the DESCRIPTION clause of an indesx object 
> why they do allow a value of zero (if they indeed do).
> Without proper explanation, I tend to reject a zero.
> 
> Would be good if we could get consensus amon reviewers
> and add something to the Guidelines document.

Here is what I put into the latest under-construction
version of the Guidelines document:

   - For integer-valued objects that appear in an INDEX clause or for
     TCs that refer to an integer-valued index column:

     - Use of Unsigned32 with a range that excludes 0 is RECOMMENDED.
       If 0 is included in the range, then a good reason MUST be
       specified.

     - Integer32 or INTEGER with a non-negative range is acceptable.
       Again, if 0 is included in the range, then a good reason MUST be
       specified.

   The above is a direct translation of the INDEX rules in RFC 2578
   Section 7.7 up to and including bullet (1).  Although not forbidden
   by RFC 2578,  using objects of type Gauge32 in an INDEX clause is NOT
   RECOMMENDED under these guidelines.

   Sometimes it will be necessary for external variables to represent
   values of an index object -- e.g., ifIndex [RFC2863].  In such cases
   authors of the module containing that object SHOULD consider defining
   TCs such as of InterfaceIndex and/or InterfaceIndexOrZero [RFC2863].

This is derived from material that Bert sent to me.

//cmh