Re: Methods, Inheritance, Exceptions, etc. (was: Re: Methods in S MIng ?)

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

>>>>> Glenn Waters writes:

Glenn> That said, what changes would be required to the
Glenn> draft-ietf-eos-rowops-00.txt document to allow for methods?
Glenn> Rowops is already specifying a new set of PDUs -- could these
Glenn> PDUs be changed to meet the existing RowOps requirements and
Glenn> the SMIng requirements?

Hard to say since the current spec does not really spell out what the
semantics of e.g. EditRowRequest-PDU really are. (Editing may imply
reading, changing, writing back - but I guess this is not what
EditRowRequest-PDU will do - perhaps the name is misleading.)

There are at least two important things to note:

(1) The behaviour of the SetRequest-PDU which requires to return the
    values in the SetRequest-PDU rather than the current values is not
    really useable for supporting method invocations.

(2) For method invocation, you want to pass (i) the name (OID?) of the
    method to invole, (ii) the name of the object or row instance on
    which you invoke a method, (iii) parameter values that are no real
    object instances in the SMIv2 sense, (iv) return values that are
    no real object instances in the SMIv2 sense, and (v) information
    about method execution error conditions (exceptions).

(3) We need to figure out what the semantics of method invocations
    should be (may be, at least once, at most once, exactly once) and
    depending on the conclusions, we need to have proper support in
    the protocol primitives.

To do all this in a clean way, you probably need to add one or more
PDU types.

About two years ago, I wrote some IDs for discussion within the NMRG
which contain some thoughts on supporting methods (we called them
operations at that time). I used SMIv2 syntax since SMIng was not on
the radar. I am not sure I totally agree with every detail I have
written back in 1999, but for those interested:

http://www.ibr.cs.tu-bs.de/~schoenw/draft-irtf-nmrg-smi-ops-00.txt
http://www.ibr.cs.tu-bs.de/~schoenw/draft-irtf-nmrg-snmp-ops-00.txt

/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/>