User manual

Chapter 6. SNMP Operation
6-2 FMUX-01Mar 2003
6.3 The Management Information Base
The management information base (MIB) includes a collection of managed objects.
Managed objects are defined as parameters that can be managed, such as specific
information on device configuring or on performance statistics values.
The MIB includes the definitions of relevant managed objects (MIB variables) for the
specific node. Various MIB's can be defined for various management purposes, types of
equipment, etc. The management data itself is a collection of integer, string and MIB
address variables that contain all the information necessary to manage the node.
A leaf object's definition includes the range of instances (values) and the "access" rights:
Read-only Instances of an object can be read, but cannot be set.
Read-write Instances of an object can be read or set.
Write-only Instances of an object can be set, but cannot be read.
Not accessible Instances of an object cannot be read, nor set.
6.4 MIB Structure
The MIB has an inverted tree-like structure (root over leaves), with each definition of
a managed instance forming one leaf, located at the end of a branch of that tree. Each "leaf"
in the MIB is reached by a unique path, therefore by numbering the branching points,
starting with the top, each leaf can be uniquely defined by a sequence of numbers. The
formal description of the managed objects and the MIB structure is provided in a special
standardized format, called Abstract Syntax Notation 1, or ASN.1 (pronounced A-S-N dot
one).
Since the general collection of MIB's can also be organized in a similar structure,
under the supervision of the Internet Activities Board (IAB), any parameter included in a
MIB that is recognized by the IAB is uniquely defined.
To provide the flexibility necessary in a global structure, MIB's are classified in
various classes (branches), one of them being the experimental branch, another being the
management (mgmt) branch, and yet another the group of private (enterprise-specific)
branch. Under the private enterprise-specific branch of MIB's, each enterprise
(manufacturer) can be assigned a number, which is its enterprise number. The assigned
number designates the top of an enterprise-specific sub-tree of non-standard MIB's. Within
this context, CTC Union has been assigned the enterprise number 4756.