Appendix B   The SilverStream SNMP Agent

Simple Network Management Protocol (SNMP) is a protocol used to remotely manage and control nodes on a TCP/IP network. Using SNMP, one workstation running management software can monitor information being collected by routers, servers, and other workstations on the system. This information is used to determine the health and performance of the network. This appendix describes how you can set up and test SNMP to monitor the SilverStream Server.

NOTE   The SilverStream SNMP implementation currently runs on the Windows NT platform only, and does not allow the SNMP service to control the SilverStream Server.

SNMP implementation overview   

SilverStream implements SNMP using three components:

• SMNP extension agent: AgSNMP35.dll

• AgSNMP.props file

• AgSNMPGetStats business object.

The SilverStream Extension Agent (AgSNMP35.dll) implements the Windows NT SNMP Application Program Interface (API). The SNMP agent reads the SilverStream Server statistical information from a flat file named AgSNMP.props that is located in the SilverStream\resources directory.

    For a list of available statistics and object identifiers, see SilverStream ID and OIDs.

How the SilverStream components work   

A SilverStream scheduled business object (AgSNMPGetStats) updates the AgSNMP.props file according to a scheduled interval. When the scheduleReached event fires, the business object gets an instance of the AgiServer object and calls the appropriate methods to build the data for the file. It then gets registry information from the server to determine the SilverStream path and writes the file to the resources directory.

On a GET request, if the update interval has elapsed, the Silverstream Extension Agent updates the MIB data by accessing the registry to get the SilverStream path and reading the AgSNMP.props file in the resources directory. Otherwise, it returns the value that was stored the last time the file was read. If the timestamp in the file is not updated within the given interval, the "Server Responding" status is set to false, indicating a possible problem with the SilverStream Server.

Process flow and terminology   

The following figure shows how the SilverStream components work within the SNMP framework.

The following terms are used in an SNMP-enabled architecture:

• Management Node. The workstation or server running one or more network management processes. These processes are usually software applications that gather information from the managed nodes, or SNMP agents. Examples of management node software include Unicenter TNG, from Computer Associates; Openview, from Hewlett Packard; and Tivoli, from IBM.

• Managed Information Bases (MIBs). The hierarchical map of all managed objects and how they are accessed.

• Managed Objects (MIB Objects or Variables). The collection of objects that describe the SNMP managed node to the management node. This data is defined with a specific set of attributes that are manipulated using the standard SNMP operations Get, GetNext, and Set.

• Object Identifier (OID). A unique identifier for an MIB variable.

• SNMP Agent. Software or firmware that runs as one or more processes on a managed server. The SNMP Agent provides management services by collecting and returning management information requested by the management node. An SNMP agent can be read-only, or it may allow the management node to control or alter the node it is managing. An SNMP agent may also generate traps, which are unrequested notifications of events.

• Extension Agent (Subagent). A DLL that implements a set of registered managed objects defined in a MIB module and communicates with the SNMP service using the SNMP API.

Setting up SNMP for the SilverStream Server    

This section describes how to set up SNMP as an NT service and run the software. Setting up SNMP involves the following steps:

1. Installing the software as a service

2. Installing SilverStream on the server

3. Enabling the AgSNMPGetStats business object

4. Testing the program

Installing SNMP as a service   

If you are installing the SNMP software service on a machine that is currently running the SilverStream Server, first you need to stop the server. In addition, if SilverStream has already been installed, you will need to reinstall SilverStream after installing the service.

To install the SMNP Service:

1. Log on to NT with administrator privileges.

2. Select the Network control panel.

3. Select the Services tab.

4. Click Add.

5. Select SNMP Service (you need the NT install CD).

6. Complete the Agent tab:

   Contact: Name of person or name of machine

   Location: Any descriptive term

7. Complete the Traps tab (optional):

   Community name: public (optional)

   Trap destinations: IP address of the machine (optional)

8. After installing the SNMP Service, the following items need to be reinstalled:
   • NT 4.0 Service Pack 5

   • Internet Explorer

Installing SilverStream on the server   

After you have installed SNMP as a service, use the SilverStream Installation program to install SilverStream on the server to be managed. If you are reinstalling SilverStream, you must stop the SNMP Service first. Otherwise, the install program will not be able to write over the AgSNMPAgent.DLL file.

The SilverStream install process takes care of the required registry key entries and places the agent in the correct location. The required registry entries are as follows:

Key:

  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SNMP\ 
  Parameters\ExtensionAgents 

Value:

  Software\SilverStream Software Inc.\SilverStream\version\SNMP\ExtensionAgents\AgSNMPAgent\CurrentVersion 

Key:

  HKEY_LOCAL_MACHINE\SOFTWARE\SilverStream Software Inc.\SilverStream\version\SNMP\ExtensionAgents\AgSNMPAgent\CurrentVersion 

Value:

  SilverStream Install Directory\bin\AgSNMPversion.dll 

Enabling the scheduled business object   

In the SilverMaster database, open the business object AgSNMPGetStats and set the Trigger value for Enabled to True. If you want to change the time interval that the business object will fire, you must change it in two places:

• Trigger Properties sheet. Change the Schedule Interval.

• General Declarations section. Change the value for m_fileUpdateInterval to match the Schedule Interval.

Testing the program   

SilverStream provides a tool that allows you to test the SNMP installation from a DOS prompt. First, open the file SilverStream\bin\SilverSNMPGetStats.bat and change the localhost parameter wherever it appears in the file to the host name on which your SilverStream Server is running. Then follow the next procedure.

To test the SNMP extension agent:

1. Stop and restart the SNMP Service.

2. Open a DOS window.

3. Change to the SilverStream\bin directory

4. Run the batch file SilverSNMPGetStats. To get a list of available parameters, type:

     SilverSNMPGetStats -? 
   

SilverStream ID and OIDs   

The SilverStream Object Identifier is composed of an enterprise ID and the OID identifying each Managed Object (MIB). You will need the following information to set up access to the SilverStream Server OIDs from your SNMP Management node:

• Private Enterprise ID. A unique number assigned to a company. The SilverStream private enterprise ID is 3068.

• Object Identifier (OID). A unique identifier that references a managed object. An OID is the location of a managed object within a MIB namespace. The OID of a MIB object is also referred to as the object's identity or registration. The SilverStream host name OID is 1.3.6.1.4.1.3068.1.7.4.1.0.

The following are the SilverStream OIDs. When accessing MIB data using SNMPTool.exe, you must precede the OID with a period.

Statistic Description	OID
Host Name OID	1.3.6.1.4.1.3068.1.7.4.1.0
Server Revision OID	1.3.6.1.4.1.3068.1.7.4.2.0
Server Start Time OID	1.3.6.1.4.1.3068.1.7.4.3.0
Data Time Snapshot OID	1.3.6.1.4.1.3068.1.7.4.4.0
Maximum Requested URL OID	1.3.6.1.4.1.3068.1.7.4.5.0
Minimum Requested URL OID	1.3.6.1.4.1.3068.1.7.4.6.0
Server Load OID	1.3.6.1.4.1.3068.1.7.4.7.0
Free Thread Count OID	1.3.6.1.4.1.3068.1.7.4.8.0
Idle Thread Count OID	1.3.6.1.4.1.3068.1.7.4.9.0
Total Thread Count OID	1.3.6.1.4.1.3068.1.7.4.10.0
Hit Count OID	1.3.6.1.4.1.3068.1.7.4.11.0
Mean Request Time OID	1.3.6.1.4.1.3068.1.7.4.12.0
Max Request Time OID	1.3.6.1.4.1.3068.1.7.4.13.0
Min Request Time OID	1.3.6.1.4.1.3068.1.7.4.14.0
Emitted Bytes OID	1.3.6.1.4.1.3068.1.7.4.15.0
Free Memory OID	1.3.6.1.4.1.3068.1.7.4.16.0
Total Memory OID	1.3.6.1.4.1.3068.1.7.4.17.0
Garbage Collection Count OID	1.3.6.1.4.1.3068.1.7.4.18.0
Idle Sessions OID	1.3.6.1.4.1.3068.1.7.4.19.0
Total Sessions OID	1.3.6.1.4.1.3068.1.7.4.20.0
Server Responding OID	1.3.6.1.4.1.3068.1.7.4.21.0