Re: Methods in the NIM requirements

[Juergen Schoenwaelder <schoenw@ibr.cs.tu-bs.de>]

>>>>> John Strassner writes:

John> No one is ignoring the MIBs and other protocols. If you would
John> actually look at one of the models, you would realize that it
John> already maps some MIB information. This was true of CIM and DEN
John> 2 years ago, and is true of the Policy models that have been
John> recently published as IETF drafts.

The CIM MIB mappings I have seen are often broken and fail to achieve
the goal of unification and overall simplification. An example from
the CIM Devices MOF specification 2.1.1:

        [Description(
          "An estimate of the current bandwidth in Bits per Second. "
          "For endpoints which vary in bandwidth or for those where "
          "no accurate estimation can be made, this property should "
          "contain the nominal bandwidth."),
         Units ("Bits per Second"), 
         MappingStrings {"MIB.IETF|RFC1213-MIB.ifSpeed", 
               "MIF.DMTF|Network Adapter 802 Port|001.5"}
        ]
    uint64 Speed;

Note that the original definition of ifSpeed is a 32 bit gauge and not
an uint64. (This document also refers to BRIDGE-MIB.dot1dTpPortMaxInfo,
which is defined as an INTEGER in the MI, but CIM defines it to be an
uint32.) [This may have all been done on purpose - but there is no
text which explains how you handle the interesting corner cases that
may show up in practice.]

I do not want to discuss this example (or others). I just want to warn
everyone that mappings are (a) not simple and (b) require that domain
experts are involved and (c) take time to get right (which requires to
have mechanisms in place to evolve NIM models over time without
causing interoperability problems).

/js

-- 
Juergen Schoenwaelder      Technical University Braunschweig
<schoenw@ibr.cs.tu-bs.de>  Dept. Operating Systems & Computer Networks
Phone: +49 531 391 3289    Bueltenweg 74/75, 38106 Braunschweig, Germany
Fax:   +49 531 391 5936    <URL:http://www.ibr.cs.tu-bs.de/~schoenw/>