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You can monitor your server in real time by using the Simple Network Management Protocol (SNMP). SNMP is a protocol used to exchange data about network activity. With SNMP, data travels between a managed device and a network management station (NMS) where users remotely manage the network.
A managed device is anything that runs SNMP (for example, hosts or routers). Your Novell® Enterprise Web Server is a managed device. An NMS is usually a powerful workstation with one or more network management applications installed. A network management application graphically shows information about managed devices (which device is up or down, which and how many error messages were received, etc.).
Every managed device contains an SNMP agent that gathers information regarding the network activity of the device. This agent is known as the subagent. Each Web server has a subagent.
Another SNMP agent exchanges information between the subagent and NMS. This agent is called the master agent. A master agent runs on the same host computer as the subagents to which it talks. You can have multiple subagents installed on a host machine. All of these subagents can communicate with the master agent.
Values for various variables that can be queried are kept on the managed device and reported to the NMS as necessary. Each variable is known as a managed object, which is anything the agent can access and send to the NMS. All managed objects are defined in a management information base (MIB), which is a database with a tree-like hierarchy.
SNMP exchanges network information in the form of protocol data units (PDUs). PDUs contain information about various variables stored on the managed device. These variables, also known as managed objects, have values and titles that are reported to the NMS as necessary. Communication between an NMS and managed device can take place in one of two forms: NMS-initiated and managed-device-initiated.
NMS-initiated communication is the most common type of communication between an NMS and a managed device. In this type of communication, the NMS either requests information from the managed device or changes the value of a variable stored on the managed device.
The following steps make up an NMS-initiated SNMP session:
If the PDU from the NMS requests that the subagent set variable values, the subagent sets these values.
This type of communication occurs when the managed device needs to inform the NMS of an event that has occurred. A managed device such as a terminal would initiate communication with an NMS to inform the NMS of a shutdown or startup. Communication initiated by a managed device is also known as a trap.
The following steps make up a managed-device-initiated SNMP session:
Each Enterprise Web Server has its own management information base (MIB). The Enterprise Web Server's MIB is a file called HTTP.MIB, which contains the definitions for various variables pertaining to network management for the Enterprise Web Server. These variables are known as managed objects. Using the Enterprise Web Server MIB and network management software, such as HP* OpenView*, you can monitor your Web server like all other devices on your network.
The Enterprise Web Server MIB has an object identifier of netscape 1 (http OBJECT IDENTIFIER : := { netscape 1 }) and is located in the server_root\PLUGINS\SNMP\MIBFILES\NETWARE directory.
You can view administrative information about your Web server and monitor the server in real time using the Enterprise Web Server MIB. The following table lists and describes the managed objects stored in the HTTP.MIB.
Table 6. HTTP.MIB Managed Objects and Description
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