SNMP MIB Modeling

1
SNMP MIB Modeling

• J. Won-Ki Hong
• Dept. of Computer Science and Engineering
• POSTECH
• Tel [phone]
• Email jwkhong_at_postech.ac.kr

2
Table of Contents

• SNMP MIB Object Modeling
• Categorize MIB Objects
• Translate Model into a MIB
• Modeling Example Car

3
SNMP MIB Modeling

• MIB is essential for developing and operating
  management systems
• SNMP MIBs are NOT object-oriented
• inheritance is not supported
• Analysis of MIB objects is required before
  writing MIB definitions
• Using the designed model, MIB definitions can be
  easily generated
• Similar to software engineering -- must design a
  system before any implementation!

4
Step1 Categorize MIB Objects

• Components
• collections of logical physical devices or
  services that are being managed
• Attributes
• fairly static properties of a modeled object
• Actions
• control a system
• Statistics
• useful information about what a system has been
  doing
• State
• the current condition of a system

5
Components

• physical or logical containment relationships?
• what does it contain?
• start from the top level and work down until
  reasonable size is reached
• physical containment?
• e.g., a list of interface cards
• logical containments?
• e.g., communication systems
• Cardinality
• how many of an item are present in a system?

6
Attributes

• the fairly static properties of the resource
  being modeled
• e.g., name, id, location, etc.
• can be refined into related groups
• Identity of an object
• determine ID by an attribute
• assign an arbitrary ID

7
Actions

• SNMP does not support explicit action operation
• represented in terms of implicit actions which do
  their work through side effects
• this is achieved by setting some value of a MIB
  object
• Need to define action goals and action steps
• action goals?
• what does the manager need to be able to do to
  the managed resource?
• action steps?
• how does it do it?

8
Statistics

• show a picture of the past
• a record of the interesting events which occurred
  since a specific point in time
• high water marks identify peaks in resource
  utilization
• all stats are considered valid for a specific
  period of time (known as epoch)
• What statistics are we interested in?

9
State

• provides insight into the current condition of
  the resource
• represents dynamic properties of the resource
• stages of operation
• e.g., enabled/disabled
• resource usage level
• e.g., queue is 50 full
• a state graph (e.g., finite state machine) can be
  used to identify possible inputs and states of
  the resource

10
Step2 Translate Model into MIB

• Generate an object analysis worksheet containing
  major components and their cardinality,
  attributes, statistics and states
• Translate the worksheet into MIB syntax
• sub-components with a cardinality greater than 0
  should be part of a table
• stats representing increasing values are Counter
  type
• stats representing high or low water marks are
  Integer type
• states representing discrete stages of operation
  are enumerated Integer type
• states that have fluctuating values are Gauge
  type
• attributes of an object can be
• Octet String - human readable descriptions or
  binary data
• Integer - measurable quantities

11
Modeling Example - CarPhysical Containments

• Engine compartment
• engine
• transmission
• climate control system
• Passenger compartment
• seats
• dashboard/instrument panel
• Chassis
• doors
• suspension system

12
Modeling Example - CarLogical Containments

• Powertrain
• engine
• transmission
• Exhaust
• manifold
• muffler

• Electrical
• spark plugs
• battery
• Environmental
• passenger compartment
• climate control
• user preferences

13
Modeling Example - CarAttributes

• Engine
• horsepower rating
• number of cylinders
• Powertrain
• drive type
• 2 or 4 wheel
• transmission type
• manual
• automatic
• of speeds

• Chassis
• fabrication date
• Passenger compartment
• seat type bench or bucket
• Electrical system
• electrical capacity
• Climate control system
• thermal rating in BTUs

14
Modeling Example - CarActions

• Powertrain
• on/off engine
• shift the gear
• Exhaust
• release smoke

• Electrical
• use/charge battery
• on/off lights
• Environmental
• on/off heat
• on/off air conditioner
• change radio channels

15
Modeling Example - CarStatistics

• Engine
• peak horsepower
• highest RPMs
• total RPMs
• trip mileage
• total mileage

• Powertrain
• number of upshifts
• number of downshifts
• Electrical system
• peak electrical requirements
• average electrical requirements

16
Modeling Example - CarStates

• Engine
• stopped/starting/running/failed
• engine speed in RPMs
• oil pressure
• fuel consumption rate
• Powertrain
• drive engaged 2 or 4
• current gear

• Chassis
• door open/closed
• Electrical system
• ok/shorted
• battery charge
• Climate control system
• engaged/off-line

17
Object Analysis Sheetfor Car Engine
Component
Cardinality
Attributes
Statistics
States
18
Engine MO Definition

• engCylTable OBJECT-TYPE
• SYNTAX SEQUENCE OF EngCylEntry
• ACCESS not-accessible
• STATUS mandatory
• DESCRIPTION This table represents the
  sub-components of an
• engine that are dependent on the of
  cylinders in the engine.
• engine 1
• engCylEntry OBJECT-TYPE
• SYNTAX EngCylEntry
• ACCESS not-accessible
• STATUS mandatory
• DESCRIPTION A row in the engine cylinder
  table. Rows cannot be created or deleted via
  direct SNMP operations.
• INDEX engCylIndex
• engCylTable 1

19
Engine MO Definition (contd)

• EngCylEntry SEQUENCE
• engCylIndex Unsigned32, -- table index
• engCylPistonSize Unsigned32, -- attributes
• engCylSparkPlugSize Unsigned32,
• engCylSparkPlugVendor OBJECT IDENTIFIER,
• engCylInjectorCapacity Unsigned32,
• engCylFuelConsumed Counter32, -- statistics
• engCylSparkPlugState INTEGER, -- states
• engCylSparkPlugSparkRate Gauge32,
• engCylInjectorState INTEGER,
• engCylInjectorFuelRate Gauge32,
• Note that the definition for each object is
  further required.

20
Summary

• Constructing a structure is the most critical
  part of MIB development
• Declaring the actual MIB objects is more of a
  task of translation than a labor or design
• Tools such as DMH MIB Compiler (www.dmhsoftware.co
  m) and MG-Soft MIB Compiler (www.mg-soft.si) can
  be used to define and compile SNMP MIB
  definitions
• READING David Perkins, Understanding SNMP MIBs,
  Prentice-Hall, Chapter 7