A modeling toolset for the analysis and design of OSI network management objects - HP's OpenView GDMO Modeling Toolset network design software, Open System Interconnection - includes partial GDMO definition for a Unix password file - Product Information

Hewlett-Packard Journal, Oct, 1996 by Jacqueline A. Bray

To deal with the complexity of network management standards and the increasing demand to deploy network management applications quickly, analysts and designers need a set of tools to help them quickly and easily model, define, and develop new network management objects.

The HP GDMO (Guidelines for the Definition of Managed Objects) Modeling Toolset (GMT) is the first tool in the HP OpenView TMN (Telecommunications Management Network) developer tool chain (Fig. 1). This toolset consists of a set of integrated tools designed to aid developers in the analysis and design of OSI network object models. The key components of the toolset are a graphical modeling tool, import and export facilities, and a conformance report generator. The tools operate independently of other HP OpenView products so that network specifiers can work independently of implementers. This article provides an overview of the network modeling process, GDMO, and the modeling tools.

The Modeling Process

The first step in developing a network object model is the analysis of the environment to be managed. The network and system resources to be managed are identified and their characteristics and the operations that can be performed upon them are defined. The managed resources might be physical (e.g., a router or workstation) or logical (e.g., a software process). A managed resource might also represent a collection of different resources. Other elements might be managed that are not actually resources but are required to support management functions, such as an event log. These requirements are translated into a GDMO object model, with the managed resources represented as managed objects. The managed objects define the interface to a managed resource.

GDMO

The Guidelines for the Definition of Managed Objects is an ISO standard (ISO/IEC 10165-4 (ITUX.722))(1) that defines how network objects and their behavior are to be specified, including the syntax and semantics. This specification language allows network object designers and manager/agent implementers to communicate designs and build upon existing designs. GDMO is an object-oriented environment, using the concepts of inheritance, containment, and encapsulation. It is used to define:

* Managed object classes for managed resources

* Attributes and behaviors of a managed object

* Operations that can be performed on an attribute or object

* Notifications (events) an object might issue

* Relationships with other managed objects

* The names of object instances.

GDMO is organized into templates, which are standard formats used in the definition of a particular aspect of the object, with rules for how these templates refer to each other. A complete object definition is a combination of interrelated templates. There are nine of these templates.

* Managed object class templates define a model for managed object instances that share the same characteristics. The inheritance relationships with other managed object classes are specified, along with the packages that define the class characteristics.

* Package templates are groups of logically related sets of behaviors, attributes, attribute groups, actions, notifications, and parameters. With each attribute is a property list of valid operations (Get, Replace, Add, and Remove), initial values, and other value characteristics.

* Behavior templates describe, in textual form, the behavior of a component.

* Attribute templates define an actual data element of an object, including its syntax and behavior.

* Attribute group templates define a set of attributes to allow operations to be performed on the group as a whole.

* Action templates define additional operations for a managed object that cannot be modeled using the standard operations defined in the package template.

* Notification templates define unsolicited events that may be sent by the agent.

* Parameter templates define error conditions specific to the object and extend the definition of information used by actions and notifications. The context within which this parameter can be used is specified.

* Name binding templates define where an object may be located in the global containment tree, along with the attribute used to distingtuish object instances. These templates also specify rules for the creation and deletion of the object instances.

An example of each of these templates can be found in Appendix A, which shows a portion of a GDMO definition for a UNIX[R] password file (i.e., /etc/password). The details of the information to be exchanged between the manager and agent are defined using ASN. 1 (Abstract Syntax Notation One).(2) ASN.1 is a formal description language used to define data types to be exchanged between systems. It includes primitive data types, such as integer and Boolean, and allows new data types to be constructed from these types. The data types are grouped into one or more ASN. 1 modules within a GDMO definition. In the example in Appendix A, there is one ASN.1 module named PasswordFilelnfo. The GDMO templates reference ASN. 1 data types by prefixing the data type with the ASN.1 module name (e.g., PasswordFilelnfo.LoginNameSyntax in the loginName attribute template).