The Simple Network Management Protocol (SNMP) has been widely used in enterprise networks to effectively manage systems, network devices, and networks. The widespread use of SNMP has raised many issues relating to managing systems and networks. One of the benefits of SNMP is how quickly solutions may be created to support the increasing numbers of networking components and applications.
Within SNMP networks, the number of entities (systems, components, and applications) that need to be managed is growing rapidly. There is a need to respond to the industry's demand for more flexible and dynamic management of multiple devices.
The initial network management solution, that is based on SNMP, allowed developers to create one monolithic agent per system/device listening on a single port (port 161). It was soon discovered that this SNMP solution had many constraints and was not flexible enough to effectively manage all the devices necessary.
New technology was needed to produce multiple agents by different people, that could manage different components and applications separately within a device. This resulted in the new extensible agent technology or Master/subagent technology. Based on this technology, Sun provides a solution named Solstice Enterprise Agent (SEA).
The agents consist of Master Agent and subagents. The Master Agent receives the SNMP-based management requests from the managers and sends responses to these management requests. The responses are sent after retrieving the appropriate values from the respective subagents. The subagents provide management of different components based on Management Information Based (MIBs or MIFs) specifically designed for components/applications.
The Enterprise Agent also allows you to integrate and use SNMP-based legacy agents.
In subsequent chapters, the roles of the Master Agent and subagents are discussed in detail.
The SNMP based component of the SEA product consists of various components.
Figure 1-1 illustrates the architecture of the SEA.
The following is a description of each of the components associated with the SEA product.
The Master Agent listens on port 161.
Subagents are zero or more processes that have access to the management information and provide manageability to various applications/components within a system. These subagents interact with the Master Agent using SNMP. These subagents do not interact with the managers directly.
The Software Development Toolkit has multiple components. It includes agent/subagent libraries, a MIB compiler, and example subagents. The MIB compiler parses a MIB and creates stub files. The stub files consist of functions that you modify and enhance appropriately to provide manageability of the respective component or application.
Legacy SNMP Agents are SNMP-based and work as monolithic entities in a system. The Enterprise Agent allows the integration of legacy SNMP agents. The legacy agents are those agents already in released products from Sun or other companies.
The Enterprise Agent technology also allows you to integrate DMI 2.0 functionality. This is accomplished through the mapper, that acts as a subagent. The mapper receives requests from the Master Agent and converts them into appropriate DMI requests, that are then sent to the DMI Service Provider. When the mapper receives the response back from the DMI Service Provider, it converts this response into the SNMP response and forwards it to the Manager through the Master Agent.
A subtree is indicated by a single oid. The Master Agent has no understanding of what this subtree is without any MIB specification. The subtree may actually be an entire MIB (e.g., 'host'), a full instance (e.g., hrDeviceDescr.42), or may not even be a subtree named in any MIB specification.
Dispatching is the communication of a management request from the Master Agent to one or more subagents. Dispatching is performed according to the Master Agent's current view of registered subtrees, and an explicitly stated algorithm.
Additional terms are described in this guide's glossary.
The Master Agent receives SNMP requests from the system managers and sends responses to these requests, after determining appropriate values from the subagents. The subagents provide management of different components based on the Management Information Base (MIB) specifically designed for such components/applications. Each subagent, when invoked dynamically, registers with the Master Agent. During registration, it informs the Master Agent of the MIB subtree it manages. For more information, refer to Chapter 3, SNMP-Based Master/Subagenton page 3-1.
The SEA technology provides a software development kit that allows you to create, release, and install subagents. Additionally, the SEA allows you to integrate and use SNMP-based legacy agents.
The Desktop Management Interface (DMI) is a set of interfaces and a service provider that mediate between management applications and components residing in a system.The DMI is a free-standing interface that is not tied to any particular operating system or management process.
Sun provides DMI based functionality for management of the Sun platforms (hardware and software) and software applications running on these platforms. The DMI subagent is one type of subagent included in the SEA product. By using DMI, you may manage various elements within most systems (for example, PCs, workstations, routers, hubs, and other network objects).
A format for describing management information (MIF)
A Service Provider entity
Two sets of APIs
An interface between management applications and the Service Provider
An interface between the Service Provider and component instrumentation
A set of services (using ONC/RPC) for facilitating remote communication
For more information, refer to Chapter 5, Using DMI.
The Master Agent acts as the primary interface between the network manager and the subagents. The requests received from the manager are parsed by the Master Agent. If necessary, the original requests are broken into multiple requests. The original request is distributed by the Master Agent based on the manageability provided by each subagent. The request is then forwarded to the appropriate subagents, which provide a response to each request. After collecting all the responses from each subagent, the final response is sent to the network manager.
Only one Master Agent presides over the Master/subagent model. The Master Agent acts as a request scheduler and dispatcher for all subscribed subagents. In addition, the subagents send traps to the Master Agent, that are then forwarded to the manager.
Figure 1-2 illustrates the Master Agent as it relates to the architecture of SEA.