This document discusses the Structure of Management Information (SMI) which defines how management information within systems is represented and exchanged between systems. SMI allows management information to be structured as tables and scalars using Abstract Syntax Notation 1 (ASN.1) data types. Object identifiers (OIDs) are used to uniquely name managed objects in a tree structure. The get operation in SNMP is described which uses variable bindings to request specific management information from an agent.

1. The Structure of Management Information (SMI)
Naming OIDs, Defining OIDs
SNMP Operations
Hamdamboy Urunov, a Ph.D. Researcher student.
Special Communication Research Center.,
Kookmin University
Seoul, South Korea

2. Content
• Structure of Management Information (SMI)
• Managed Information Base (MIB )
• Management Object (Object & Instance)
• SNMP configuration
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3. Structure of Management Information - SMI
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DIFFICULT TO UNDERSTAND - SMI?
To make the definition of (new) MIBs easier
• The SMI helps MIB designers
• The SMI defines the syntax
 The SMI allows tools to be build
Question ?!
For what is the SMI being used?
What is the purpose of the SMI?
SMIv1: RFC 1155
RFC 1212: concise MIB Definitions extends SMIv1
SMIv2: RFC 2578
RFC 2579: Textual Conventions definition of new types
Answer !

4. 4
Why is the SMI discussed in this presentation?
• not to learn you how to write large MIBs
• but to learn you how to READ MIBs
Understand MIB definitions from internet – drafts and RFCs
Structure of Management Information – SMI (0)
How information in system?
How defined management information system?

5. 5
Structure of Management Information – SMI (1)
1. How Management information, which is stored within a system,
may look like
2. How management information which is transported between systems
may look like

6. 6
Structure of Management Information – SMI (2)
Management information within managed systems must be represented as:
• TABLES
=two dimensional arrays of scalars
•SCALARS
OF type Integer, Character, …
Like “current time”
“Number of packets received
from system current time”
Two dimensional arrays of scalars
Create a structure of scalars
the SNMP protocol can only exchange (a list of) scalars defined in terms of ASN.1
constructs

7. 7
Structure of Management Information – SMI (2-1)
For instance:
http://net-snmp.sourceforge.net/dev/agent/group__scalar.html#ga667f2bdbbc51e546741a97cc81c3ad75

8. 8
Structure of Management Information – SMI (2-2)
http://www.net-snmp.org/dev/agent/scalar__int_8c-example.html

9. 9
• One can not READ/WRITE table with 1 operation
• to GET a table, one should READ each individual element
• this is complex
Structure of Management Information – SMI (3)
How to exchange managed information?
Answer!!

10. 10
Structure of Management Information – SMI (4)

11. 11
Structure of Management Information – SMI (5)

12. 12
Structure of Management Information – SMI (6)

13. SMI: Data type for scalars
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1
Counts from 0.. Max int can also count
back (decrement)
Compare to speed indicator
Can not wrap
This type is important speed of the car
(machine)

14. 14
SMI: Data type for scalars (cont..)

15. 15
SMI: Data type for scalars (cont..)

16. 16
Example of scalar objects

17. 17
Example of scalar objects (cont…)

18. Object Naming
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How can the manager identity, for example, the address, name AND uptime
INTRODUCE a NAMING TREE
THE LEAVES OF THE TREE REPRESENT THE MANAGED OBJECTSNODES ARE
INTRODUCED FOR NAMING PURPOSES

19. 19
Object Naming (CONT..)
Object IS THE DEFINITION
Instance has a value
How about Scalar and Instance!
In the case of scalars:
Distinction between object and instance not useful
In the case of tables :
The object defines how rows look like
There may be multiple INSTANCES of that OBJECT
THUS there can be multiple rows
The case of tables the distinction is useful

20. 20
Object Naming (CONT..)

21. 21
Object Naming (CONT..)

22. Object type definition
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23. 23
Object type definition - Example

24. 24
Definition of non-leaf “Objects”

25. Definition of a MIB
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26. Module Identity - Example
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27. 27
Module Identity – Example-1

28. Tables
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29. Naming of Entries
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30. 30
Naming of Entries (cont…)

31. 31
Naming of Entries (cont…)

32. Result
32
Difference between object and instance

33. Naming of table entries - Example
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34. Table indexing – Index value
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35. 35
Table indexing – Index value

36. 36
Table indexing – Index value

37. Table indexing – Multiple index field
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38. 38
Table indexing – Multiple index field

39. Table definition
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40. 40
Table definition

41. 41
Table definition (cot…)

42. 42
Table definition (cot…)

43. 43
Definition of new types

44. 44
Textual conventions

45. 45
Row-status textual convention

46. Row-status - Example
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47. Row-status – Example-1
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48. 48
Row-status – Example-2

49. Notification types
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50. 50
Notification types - 1

51. 51
Notification types - 2

52. 52
Notification types - 3

53. Object group constructor
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54. A Standard For Managed Information
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http://www.cnblogs.com/klchang/p/5189180.html

55. Naming OIDs
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Managed objects
Managed Objects are organized into a treelike
hierarchy. This structure is the basis for SNMP’s
naming scheme.
An object ID An object ID is made up of a series of integers based
on the nodes in the tree, separated by dots (.).

56. 56
Naming OIDs (cont…)
• The first line declares internet as the OID 1.3.6.1,
• which is defined (the ::= is a definition operator) as
• a subtree of iso.org.dod, or 1.3.6.
• The last four declarations are similar, but they define the other branches that belong to internet.
• For the directory branch, the notation { internet 1} tells us that it is part of the internet sub-tree and
that its OID is 1.3.6.1.1. The OID for mgmt is 1.3.6.1.2, and so on.

57. 57
Naming OIDs (cont…)
entreprises OBJECT IDENTIFIER ::= { private 1 }
 There is currently one branch under the private subtree.
 It’s used to give hardware and software ability to define their own private objects
 for any type of hardware or software they want managed by SNMP.

58. 58
Naming OIDs (cont…)
 With your own enterprise number, you can create your own private MIB that allows
you to monitor exactly what you want.
Every object definition has the following format:

59. A Closer Look at MIB-II
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60. 60
SNMP Operations, the get Operation
How did the agent know what the NMS was looking for?
One of the items in the get request is a variable binding.
 A variable binding, or varbind, is a list of MIB objects that allows a request’s recipient to
see what the originator wants to know.
 Variable bindings can be thought of as OID=value pairs that make it easy for the
originator (the NMS, in this case) to pick out the information
 it needs when the recipient fills the request and sends back a response.
$ snmpget -v 1 -c public cisco.ora.com .1.3.6.1.2.1.1.6.0
system.sysLocation.0 = ""

61. Thank you
hamdamboy.urunov@gmail.com
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