This guide provides formatted information drawn primarily from
the MIB files written for the Server Administrator services that support
the SNMP protocol.
For each of the variables defined in the MIBs, the following fields
are specified:
- Variable name
- OID or unique identifying number
- Description
- Data type of the variable (for example: integer, string, octet
string)
- Whether the variable is accessible, not accessible, or read-only
- Index or indexes, if applicable
For each MIB group that has unique variable definitions, tables
are included in the last section of the section to explain the meaning
of the terms.
Standards for writing MIBs are defined by the Internet Engineering
Task Force (IETF). Structure of Management Information (SMI) is a
standard that specifies the rules for defining the structure and type
of managed objects and events in a MIB. SMIv1 is specified in Request
For Comments (RFC) 1155. The Server Administrator MIB conforms to
the SMIv1 standard.
SNMP is a systems management standard originally designed for network
management. SNMP manages much more than networks. Information Technology
(IT) professionals use SNMP for monitoring and managing computer systems
and the various components and peripherals supported by their systems.
SNMP standards are defined by the Internet Engineering Task Force
(IETF). SNMP version 1 was published in August 1988 and is the most
commonly supported version of SNMP. SNMP version 2 was first published
in May 1993, but has not gained widespread market acceptance. SNMP
version 3 was recently completed and has addressed security issues
that exist in version 1.
All SNMP systems consist of one or more managed systems that provide
data through an SNMP agent to a management system. The management
system provides a user interface to view data from the managed systems.
The management system and managed systems communicate over a network
(typically through User Datagram Protocol/Internet Protocol [UDP/IP]).
The management system and a managed system communicate by means
of a common data schema. SNMP MIB files define the structure, type,
and values of the SNMP data. While MIBs can be standardized or enterprise
specific, most operating systems supply SNMP agents for the standard
MIB-I and MIB-II schemas. MIB-I defines a base set of standard management
information for systems implementing the Internet Protocol (IP) suite.
MIB-II defines characteristics of the system, characteristics of network
interfaces, and characteristics of components of the IP on the system.
In addition to the standard MIBs, many hardware vendors have defined
MIBs that provide management data specific to their systems and peripheral
devices.
Monitored data can be retrieved through SNMP using the Get command.
Typically, this command requires the host name or IP address of the
target machine as well as the OID of the data to retrieve. Exact details
are dependent on the operating system and the development tools being
used to create the management application. The Get command has a variant
known as GetNext.