White Paper - Remote Management SNMP SubAgent

These can be deleted and complete repository may be cleared by the management applications. SEL
event record follows a format [6]. The management applications parse this information, get the time
stamp, data on event, and sensor, etc.
5. SDR Repository and Sensor Model
The SDR repository is a single non-volatile storage area that contains all the system SDRs. Its records
contain information about the type and number of platform sensors, threshold support, event
generation capabilities and type of readings provided by the sensor. SDR also include records
describing the number and type of devices that are connected to the system.
The monitoring information from sensors such as temperature, voltages, fan status, etc is provided by
the IPMI Sensor Model. This provides an abstraction between management software and hardware.
Sensors are classified according to the type of reading they provide and/or the type of events they
generate; sensor can return either an analog or discrete reading. Sensors can be also be classified into
two types; linear and non-linear sensors. Linear sensors have constant accuracy, tolerance and
resolution over their raw readings. Using a linear conversion formula, linear sensors readings can be
converted into the desired sensor units such as temperature, voltage, etc. Non-linear sensors do not
have constant conversion factors, accuracy, tolerance and/or resolution over the raw readings. This
means that the polling of such sensor is two-step process. After getting the raw reading, the get
sensor reading factors should be retrieved by the management software.
6. Out-of-Band SNMP Agent in BMC
The BMC has SNMP agent running with a limited capability to support the generation of SNMP traps.
This has OOB support for management applications. If supported, PEF (Platform Event Filtering)
provides a mechanism for configuring this agent to take selected actions on the event messages. The
BMC maintains the PEF event filter and policy tables, those can be configured by management
applications. For every event message (for example, a new entry into the SEL), the agent performs
the event filtering task based on the event data to select which action should be triggered. After
successful match of event from event filter table, the corresponding action is performed. These
actions include operations such as system power off, system reset, as well as triggering the
generation of IPMI Alerts. The actions are sorted and high priority action (for example, power off) is
performed first. If action is sending an alert, the agent looks for Alert in the Alert policy table; this
policy may have collection of one or more alert destinations. OOB agent sends the SEL event in the
PET format, [7], as a SNMP trap, to all the alert destinations. The fields of SNMP massage are shown
in Exhibit 2. The specific-trap and variable-bindings fields carry the heart of the PET information. The
content and definition of these fields are specification is specified Exhibit 3 in and Exhibit 4
respectively.
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