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Abstract -- Object Evaluator Management Function
N3: Network Management
Object Evaluator Management Function
- Choi, Taesang
- Choi, Deokjai
- Tang, Adrian
In service management, there is a need to evaluate the quality of service of a
service type object or the performance of a server object. This management
function provides the capability for a manager to evaluate such managed
objects. It introduces a managed object class called the objectEvaluator. An
object evaluator (i.e., an instance of the objectEvaluator managed object
class) encapsulates the evaluation function which is used to evaluate a given
managed object in a periodic basis. After the managed object is evaluated at
the end of each evaluation period, the result is stored in the object
evaluator. By polling the result attribute of the object evaluator, the manager
can find out the latest evaluation of the managed object.
A number of object evaluators can be associated with the same managed object.
This is not surprising since a managed object can be evaluated in a number of
ways. For example, the performance of an Ethernet network can be measured in
terms of the performance of the MAC level, such as the number of the Ethernet
frames sent and the number of the Ethernet frames dropped. It can be also
measured in terms of the performance of the application servers (such as files
servers or database servers) running in the network. In this simple example,
we can thus associate at least two object evaluators with a managed object
representing some Ethernet network. Each object evaluators encapsulates a
particular evaluation function to evaluate the given managed object.
By storing the evaluation function and the evaluation period in an object
evaluator, the manager essentially instructs its agent to apply the evaluation
function at the end of each evaluation period. The following lists the
advantages of having the evaluation performed by the agent instead of the
To give an example of how an evaluation function can be used, let us consider
the performance of a router managed object. Imagine that the router object has
a number of performance attributes including the number of packets processed
and the number of packets dropped. A high level manager, when polling for the
performance of this router,may not care about specific values of these
performance attributes; instead, it may be interested in only an aggregate
health index which is evaluated by some evaluation function (e.g., one taking
a weighted linear sum) on only those performance attributes which the manager
is interested in. Used in this manner, an evaluation function can be viewed
as an aggregation function deriving a composite value from simple values such
as attribute values appearing in a managed object. Aggregation is not a new
concept; the important point is that the aggregation is performed by the
agent instead of the manager. Using an object evaluator, the manager
instructs an agent how to perform the aggregation, turning a passive agent
to be a smarter one. This technique of delegating resposibility to agents is
extremely useful in an enterprise environment.
- Since the agent has more up-to-date informaion of the managed object and
its environment, its evaluation would be more accurate than one performed
by the manager.
- If the manager has to perform the evaluation, it has to retrieve from the
agent all the environmental information which is needed by the evaluation
function; this will increase the network traffic load.
- If the manager (e.g., an enterprise manager) happens to manage quite a
number of managed resources, it would be computationally intensive for the
manager to carry out all the evaluations. It would be better for the manager
to delegate the evaluation responsibility to its agent(s).
Section 2 describes the design of the objectEvalutor managed object class.
We also examine two subcalsses of the objectEvaluator managed object class.
These subclasses contain a constraint which is applied to the evaluated
result at the end of each evaluation period. At the end of the section,
we give a Health Monitoring Management model.
In Section 3, we show how to apply the Health Monitoring Management model to
perform backup management in an enterprise environment. For our discussion,
the less-than-threshold-objectEvaluator object in the Health Monitoring
Management Model is called a "health monitor".
In Section 4, we conclude our work.