Familiarity with the background and fundamentals of SNMP, Object Identifiers (OIDs) and Management Information Base (MIB) is useful in understanding the concepts presented in this white paper. As networks have grown and additional components added (for example, routers, switches, hubs, servers, printers, workstations, and SANs), the management of enterprise networks has become very complex and expensive. Software management tools based on SNMP, such as HP SIM, were created to enable remote network administrators to manage network performance, find and solve network problems, and plan for network growth.
Device management is made possible with SNMP through a predefined Management Information Base (MIB), which describes the manageable attributes of a network object. The architecture of SNMP management is comprised of the following four basic components:
Managed nodes with an SNMP agent that provides remote access to management instrumentation. In the implementation described in this white paper, this is the JBoss snmp-adaptor.
At least one SNMP manager. For example, HP SIM or some other SNMP manager.
A management protocol used to convey management information between the agents and managers. In other words, SNMP.
Definitions of management information known as the MIB.
The following figure shows the relationship between these four components:
The management station receives and sets objects in the MIB, and an agent notifies the management station of significant but unsolicited events called traps. All communication between the management station and its agents take place using SNMP.
The structure of management information (SMI), an SNMP standard, defines the rules for how MIB objects are structured, described, and organized. The SMI allows devices to communicate by ensuring that they use a strict data representation for all management information. SMI standards are designed to define the following information elements in SNMP:
The general characteristics associated with all MIB objects. SMI defines the standard by which all MIB objects are described.
The different types of MIB objects that can be created, such as integers, strings, and more complex data types.
A hierarchical structure for naming MIB objects.
The management information associated with each MIB module.
Each object in the MIB has an object identifier (OID), which the management station uses to request the object's value from the agent. An OID is a sequence of integers that uniquely identifies a managed object by defining a path to that object through a tree-like structure called the OID tree. When an SNMP agent needs to access a specific managed object, it traverses the OID tree to find the object. The MIB object identifier hierarchy and format for the enterprise (generic) HP MIB is shown in the following figure.
In this hierarchy, each HP MIB object that the SNMP Agent software manages has a unique object identifier. A prefix of .1.3.6.1.4.1.11 points to the objects in the private HP MIB for the SNMP Agent software. There are more MIBs that reside under the private HP MIB. Each describes management information for a specific HP device, application, or other managed object.
The size of the MIB and the number of OIDs varies depending on management complexity. For instance, a MIB for the management of a LaserJet Series 4050 printer (OID prefix .1.3.6.1.4.1.11.2.3.9.4.2.1.1.2.59) has over 800 OIDs. The OID .1.3.6.1.4.1.11.2.3.9.4.2.2.13.4.1.11 maps to the object type prtmediapathstatus, which when queried by the SNMP agent, returns status information about the media path. For more information regarding the MIB for the HP LaserJet printer in this example, see:
http://www.oidview.com/mibs/11/LaserJet-Series4050-MIB.html
Although JBoss does have a private enterprise OID (18016), JBoss elected not to use it in their SNMP adaptor solution. The JBoss OID does not contain any MIBs below it, as depicted in Figure 2. Rather, JBoss uses an enterprise OID of 1.2.3.4.5.6.7 defined in the notifications.xml file that is supplied by JBoss. This file is described in the“Configuring the SNMP Service” section.
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