New overview text in Chassis MIB

[[e-mail] (Keith McCloghrie)]

Folks,

I'm in the middle of generating comments on Dave's latest update
of the Chassis MIB draft.  One item in particular is providing
some text that I would like to suggest be added in the Overview, 
concerning the applicability of this MIB (remember the "size of Texas"
comment Jeff made in the wg's first meeting.)  Another is some text
concerning multiple agents implementing this MIB for the same chassis.

I hope I have captured the consensus reached in discussions at wg 
meetings and via email, but I thought it might be useful to get 
your feedback on this text before asking Dave to add it to the draft.

Thanks,
Keith.
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   5.5  What is a "Chassis"

   This MIB applies to a chassis.  In its normal sense, a "chassis" is 
   a collection of traditionally discrete network devices packaged in 
   a single cabinet and power supply.  Indeed, the descriptions of the 
   objects are phrased assuming such a "physical" chassis.  However, 
   these descriptions are not intended to exclude the application of
   this MIB to a "logical chassis".  Examples of such logical chassis 
   might be:

   - a building containing many network devices, where each room in the
   building might be considered as a logical "slot", 

   - a geographical area containing many network devices, where each
   building in the area might be considered as a logical "slot".

   Note also that the MIB implementations for multiple (physical or 
   logical) chassis might be arranged hierachically, i.e., a module/entity
   represented in one agent's chassis MIB might in fact represent a whole 
   (lower-level) chassis.  For example, in a equipment cabinet having 
   multiple shelves with each shelf having multiple plug-in cards, the 
   whole cabinet could be represented by an overall chassis MIB in which 
   each "slot" represents a shelf, and there might also be individual 
   chassis MIBs for each shelf in which each slot represents where the 
   plug-in cards live.

   5.6  Multiple Instanciations

   For each (logical or physical) chassis, it is possible to have multiple
   agents implement this MIB for the same chassis.  However, there is no 
   requirement to have more than one agent per chassis implement this 
   Chassis MIB.  When multiple agents do implement this MIB for the same
   chassis, there is no "master" (in the sense of a point of control), 
   and each agent must implement all mandatory parts of the MIB and each 
   contain information on all entities/modules/segments in the chassis.
   Furthermore, the information in each such agent must be semantically
   identical (i.e., absolute values must be identical, and relative values
   must be equivalent).