Entity Sensor Management Information Base
Extracted elements (22)
No specialized sensor thresholding mechanisms are defined in this MIB; instead, it is recommended that a generalized thresholding MIB such as the Alarm and Events groups of the RMON MIB (RFC 2819) be used, to avoid duplicating threshold functionality.
The triple of (EntitySensorDataType, EntitySensorDataScale, EntitySensorPrecision) is used jointly to fully specify the semantics of an EntitySensorValue, allowing a single integer value type to represent a wide range of physical measurements with appropriate precision and scale.
The Entity Sensor MIB uses a SPARSE-AUGMENTS relationship with the entPhysicalTable (indexed by entPhysicalIndex), meaning entPhySensorEntry rows exist only for entities where entPhysicalClass equals 'sensor(8)'.
An EntitySensorDataType object SHOULD be defined together with objects of type EntitySensorDataScale and EntitySensorPrecision; these three types together identify the semantics of an EntitySensorValue object.
An entPhySensorEntry SHOULD be created at the same time as the associated entPhysicalEntry, and SHOULD be destroyed if the associated entPhysicalEntry is destroyed.
EntitySensorPrecision SHOULD be set to '0' when the associated entPhySensorType value is not a fixed-point type (e.g., percentRH, rpm, cmm, or truthvalue).
For sensor types voltsAC, voltsDC, amperes, watts, hertz, celsius, or cmm, an EntitySensorValue object MUST contain a fixed-point number ranging from -999,999,999 to +999,999,999; -1000000000 indicates underflow and +1000000000 indicates overflow.
If the associated EntitySensorDataType is percentRH(9), then the EntitySensorValue MUST contain a number ranging from 0 to 100.
If the associated EntitySensorDataType is truthvalue(12), then EntitySensorValue MUST contain either true(1) or false(2).
Implementation of the entityPhysicalGroup (from Entity MIB) is REQUIRED for agents that implement the Entity Sensor MIB, since entPhySensorEntry is a sparse augmentation of entPhysicalTable.
The entPhySensorType and entPhySensorScale objects SHOULD be set by the agent during entry creation, and their values SHOULD NOT change during operation.
EntitySensorDataScale is a textual convention representing SI prefix scaling factors as powers of 10, ranging from yocto(1) (10^-24) through yotta(17) (10^24), used together with EntitySensorDataType to determine actual data units.
EntitySensorDataType is a textual convention defining 12 sensor measurement types: other(1), unknown(2), voltsAC(3), voltsDC(4), amperes(5), watts(6), hertz(7), celsius(8), percentRH(9), rpm(10), cmm(11), and truthvalue(12).
EntitySensorPrecision is a textual convention (Integer32, -8..9) where positive values (1-9) indicate decimal places in the fractional part of a fixed-point sensor value, negative values (-8 to -1) indicate number of accurate digits, and zero indicates the value is not fixed-point.
EntitySensorStatus is a textual convention with three states: ok(1) indicating the agent can obtain the sensor value, unavailable(2) indicating the agent presently cannot, and nonoperational(3) indicating the agent believes the sensor is broken.
EntitySensorValue is a textual convention (Integer32, -1000000000..1000000000) representing the sensor reading. The value -1000000000 indicates underflow and +1000000000 indicates overflow for applicable sensor types.
entPhySensorUnitsDisplay is an SnmpAdminString providing a textual description of the data units for display of entPhySensorValue, determined by entPhySensorType and entPhySensorScale.
entPhySensorValueTimeStamp records the value of sysUpTime at the time the agent last updated the sensor status and/or value. This is only relevant when entPhySensorValueUpdateRate is greater than zero.
entPhySensorValueUpdateRate (Unsigned32, in milliseconds) indicates the agent's polling update frequency. The value zero indicates the sensor value is updated on demand, event-driven, or the update rate is unknown.
The entPhySensorTable provides a sparse augmentation of the entPhysicalTable for entries representing physical sensors (entPhysicalClass = 'sensor(8)'). Each row contains sensor type, scale, precision, value, operational status, units display, value timestamp, and update rate.
This document registers the ENTITY-SENSOR-MIB module under mib-2 99 (OID { mib-2 99 }), with the entitySensorValueGroup as the single mandatory object group for conformance.
The entPhySensorValue object may expose sensitive physical sensor readings (e.g., temperature, voltage, fan RPM) of a device. SNMPv1 provides no access control, so implementors are recommended to use SNMPv3 with USM (RFC 3414) and VACM (RFC 3415) to restrict access to authorized principals only.