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Site/SunNet/Domain Manager products are platforms upon which
to develop management capabilities and explore issues surrounding the management
of complex, heterogeneous environments. It also provides a set of tools for
managing those networks.
Site/SunNet/Domain Manager includes a set of agents for managing
Sun computers as well as standards-based mechanisms for managing products
from other vendors. This set is not exhaustive. The Site/SunNet/Domain Manager
agents are intended as examples of the kinds of management one can do as
well as providing useful functionality in and of themselves.
Site/SunNet/Domain Manager is designed for extensibility
and includes a number of mechanisms to support customization. This section
focuses on the features for one of those areas--writing new agents. It is
intended for Site/SunNet/Domain Manager users who have requirements beyond
those served by the agents included in this release.
The Site/SunNet/Domain Manager design is based on the manager/agent
model in the Open Systems Interconnection (OSI) management framework. The
manager is a process started by the user (for example, the Console). The agent
is a process that collects data from the managed object and reports it to
the manager.
Figure 10-1
shows the manager and agent relationship.
The Manager/Agent Services libraries provide the management
infrastructure and handle the communication services. The agent and manager
need not be concerned with the underlying networking involved in their communication.
The agent process need be concerned only with collecting data from the managed
object. The manager and agent processes make use of the Services through Application
Programming Interfaces (APIs).
Another aspect of the manager/agent model involves the definition
of management data. Emerging open management standards (for example, OSI and
the Simple Network Management Protocol (SNMP)) specify that agents abstract
the properties (or attributes) of managed objects into data items (for example,
"how busy a CPU is" becomes a value between 0 and 100). In Site/SunNet/Domain
Manager, the attributes for a managed object are described in a portion of
the Management Database (MDB)--the agent schema. The agent is able to respond
to the manager's request, because both use the same data definitions for the
managed object.
See the introductions to the Administration Guide for a
discussion of the overall architecture and how the agent fits in.
All Site/SunNet/Domain Manager agents communicate with the
manager in the manner just described. Agent types differ in the relationship
with their respective managed objects.
Agents can directly or indirectly access managed objects.
Most of the agents provided with Site/SunNet/Domain Manager manage objects
on the Sun workstations where they are installed (for example, the hostmem
agent uses the same mechanism as netstat -m to get memory utilization
data).
The second type of agent provides the ability to manage
objects that are not directly accessible. Such agents are called proxy agents.
Proxy agents run on Sun workstations, called proxy systems, and use protocol
translation mechanisms to provide the necessary access to the managed objects.
The proxy system may be the workstation on which the Console is running or
another workstation on the network.
The ping proxy agent provides the ability to test the reachability
of Internet Protocol (IP) devices, translating manager requests into Internet
Control Message Protocol (ICMP) echo requests. Similarly, the hostperf proxy
agent uses the rstat protocol to gather host statistics.
Proxy agents provide a mechanism allowing Site/SunNet/Domain
Manager to extend into virtually any domain. The Simple Network Management
Protocol (SNMP) proxy agent provides the ability to manage any device that
supports SNMP, the widely accepted standard management protocol for the TCP/IP
world.
From a high-level viewpoint, the steps involved in implementing
an agent are as follows:
- 1.
Access to the managed object must exist (that
is, code must be written to get the required management data).
NOTE - The prefixes NETMGT
, Netmgt, and netmgt are reserved for network management
functions.
- 2.
Assign a name to each discrete management
data item--attribute. For example, if the input packet count is an attribute,
ipkts would be a good name.
- 3.
Determine the data type for each attribute.
In the example, ipkts is an integer.
- 4.
Use the attribute information to
form the agent schema file, the portion of the Management Database specific
to the particular agent.
- 5.
Expand the original code written
for accessing the managed object to incorporate the agent schema definitions.
- 6.
Write the code that uses
the Agent Services library. This includes code for agent initialization, request
handling, and error reporting.
- 7.
Incorporate any agent-specific
error messages into the agent schema file.
- 8.
Test and integrate
the completed agent code and schema file.
The next three chapters
provide detailed descriptions of the procedures for incorporating a new agent.
Step 1 is not addressed
in this document. As exemplified by the set of Site/SunNet/Domain Manager
agents, managed objects can be anything from a communications interface to
a host CPU to an application program. It is impossible to generalize how to
access a managed object. One hint: Investigate whether utilities already exist
that provide access to useful information. Most of the agents in Site/SunNet/Domain
Manager rely on such mechanisms.
Steps 2, 3, 4, and 7
are addressed in
Chapter 11,
"Writing an Agent Schema
."
Steps 5, 6, and 7 are
discussed in
Chapter 12,
"Procedure for Writing an Agent
," and in Chapter 14, "Converting
an Existing Application to an Agent
."
Step 8 is covered in
Chapter 13,
"Testing and Integration
."
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Copyright 1996 Sun Microsystems, Inc.,
2550 Garcia Ave., Mtn. View, CA 94043-1100 USA. All Rights Reserved