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SIZE constraint language for InetAddress index objects indraft-ietf-ops-rfc3291bis-01.txt



Howdy,

I notice that draft-ietf-ops-rfc3291bis-01.txt now includes the
following language in the InetAddress DESCRIPTION clause:

            When this textual convention is used as the syntax of an
            index object, there may be issues with the limit of 128
            sub-identifiers specified in SMIv2, STD 58. In this case,
            the object definition MUST include a 'SIZE' clause to
            limit the number of potential instance sub-identifiers
            or else the applicable constraints MUST be stated in
            the appropriate row DESCRIPTION clauses."

This does not quite agree with Section 4.6.5 of
<draft-ietf-ops-mib-review-guidelines-01.txt>. I thought we had
agreed on something along the following lines, which does agree with
the guidelines document:

            When this textual convention is used as the syntax of an
            index object, there may be issues with the limit of 128
            sub-identifiers specified in SMIv2, STD 58.  In this case,
            the object definition MUST include a 'SIZE' clause to
            limit the number of potential instance sub-identifiers
            or else the applicable constraints MUST be stated in the
            appropriate conceptual row DESCRIPTION clause or in the
            surrounding documentation if there is no single DESCRIPTION
            clause that is appropriate."

The attached message explains the rationale.

Mike
--- Begin Message ---
On Mon, 24 Mar 2003, Juergen Schoenwaelder wrote:
> >>>>> Wijnen, Bert (Bert) writes:
> 
> Bert>    When this textual convention is used as the syntax of an
> Bert>    index object, there may be issues with the limit of 128
> Bert>    sub-identifiers specified in SMIv2, STD 58. In this case,
> Bert>    the object definition MUST include a 'SIZE' clause to
> Bert>    limit the number of potential instance sub-identifiers
> Bert>    or else the applicable constraints MUST be stated in the
> Bert>    appropriate conceptual row DESCRIPTION clauses or in the
> Bert>    surrounding documentation if there is no single DESCRIPTION
> Bert>    clause that is appropriate."
> 
> I might be missing the point. But can someone provide an example
> where there are multiple appropriate row DESCRIPTION clauses?

What happens if you have index variables inetAddressTypeX and
inetAddressX (of the obvious types) in tableX, and these are also
used as indices in extension tableZ, which has additional index
variables inetAddressTypeZ and inetAddressZ?  The size constraints
that have to be met (simultaneously) are:

sizeof(inetAddressX) is less that some value determined by the
structure of tableX

and

sizeof(inetAddressX) + sizeof(inetAddressZ) is less that some
value determined by the structure of tableZ.

Where should you document these constraints?  It seems best to put
them in one place, since they are related and must be simultaneously
satisfied, but to me it does not seem entirely appropriate to do
this in either tableX's or tableZ's row object DESCRIPTION clause.

//cmh

--- End Message ---