RMON MIB

Alarm Table
Event Table
Log Table

 

Alarm Table

UP_ARROW138B.GIF (883 bytes)
Implementation of the Alarm group is optional.

The Alarm Group requires the implementation of the Event group.

The Alarm group periodically takes statistical samples from variables in the probe and compares them to thresholds that have been configured. The alarm table stores configuration entries that each define a variable, polling period, and threshold parameters. If a sample is found to cross the threshold values, an event is generated. Only variables that resolve to an ASN.1 primitive type of INTEGER (INTEGER, Counter, Gauge, or TimeTicks) may be monitored in this way.

This function has a hysteresis mechanism to limit the generation of events. This mechanism generates one event as a threshold is crossed in the appropriate direction. No more events are generated for that threshold until the opposite threshold is crossed.

In the case of a sampling a deltaValue, a probe may implement this mechanism with more precision if it takes a delta sample twice per period, each time comparing the sum of the latest two samples to the threshold. This allows the detection of threshold crossings that span the sampling boundary. Note that this does not require any special configuration of the threshold value. It is suggested that probes implement this more precise algorithm.

Field Descriptions

alarmIndex An index that uniquely identifies an entry in the alarm table. Each such entry defines a diagnostic sample at a particular interval for an object on the device.
alarmInterval The interval in seconds over which the data is sampled and compared with the rising and falling thresholds. When setting this variable, care should be taken in the case of deltaValue sampling - the interval should be set short enough that the sampled variable is very unlikely to increase or decrease by more than 2^31 - 1 during a single sampling interval.

This object may not be modified if the associated alarmStatus object is equal to valid(1).

alarmVariable The object identifier of the particular variable to be sampled. Only variables that resolve to an ASN.1 primitive type of INTEGER (INTEGER, Counter, Gauge, or TimeTicks) may be sampled.

Because SNMP access control is articulated entirely in terms of the contents of MIB views, no access control mechanism exists that can restrict the value of this object to identify only those objects that exist in a particular MIB view. Because there is thus no acceptable means of restricting the read access that could be obtained through the alarm mechanism, the probe must only grant write access to this object in those views that have read access to all objects on the probe.

During a set operation, if the supplied variable name is not available in the selected MIB view, a badValue error must be returned. If at any time the variable name of an established alarmEntry is no longer available in the selected MIB view, the probe must change the status of this alarmEntry to invalid(4).

This object may not be modified if the associated alarmStatus object is equal to valid(1).

alarmSampleType The method of sampling the selected variable and calculating the value to be compared against the thresholds. If the value of this object is absoluteValue(1), the value of the selected variable will be compared directly with the thresholds at the end of the sampling interval. If the value of this object is deltaValue(2), the value of the selected variable at the last sample will be subtracted from the current value, and the difference compared with the thresholds.

This object may not be modified if the associated alarmStatus object is equal to valid(1).

alarmValue The value of the statistic during the last sampling period. For example, if the sample type is deltaValue, this value will be the difference between the samples at the beginning and end of the period. If the sample type is absoluteValue, this value will be the sampled value at the end of the period.

This is the value that is compared with the rising and falling thresholds.

The value during the current sampling period is not made available until the period is completed and will remain available until the next period completes.

alarmStartupAlarm The alarm that may be sent when this entry is first set to valid. If the first sample after this entry becomes valid is greater than or equal to the risingThreshold and alarmStartupAlarm is equal to risingAlarm(1) or risingOrFallingAlarm(3), then a single rising alarm will be generated. If the first sample after this entry becomes valid is less than or equal to the fallingThreshold and alarmStartupAlarm is equal to fallingAlarm(2) or risingOrFallingAlarm(3), then a single falling alarm will be generated.

This object may not be modified if the associated alarmStatus object is equal to valid(1).

alarmRisingThreshold A threshold for the sampled statistic. When the current sampled value is greater than or equal to this threshold, and the value at the last sampling interval was less than this threshold, a single event will be generated. A single event will also be generated if the first sample after this entry becomes valid is greater than or equal to this threshold and the associated alarmStartupAlarm is equal to risingAlarm(1) or risingOrFallingAlarm(3).

After a rising event is generated, another such event will not be generated until the sampled value falls below this threshold and reaches the alarmFallingThreshold.

This object may not be modified if the associated alarmStatus object is equal to valid(1).

alarmFallingThreshold A threshold for the sampled statistic. When the current sampled value is less than or equal to this threshold, and the value at the last sampling interval was greater than this threshold, a single event will be generated. A single event will also be generated if the first sample after this entry becomes valid is less than or equal to this threshold and the associated alarmStartupAlarm is equal to fallingAlarm(2) or risingOrFallingAlarm(3).

After a falling event is generated, another such event will not be generated until the sampled value rises above this threshold and reaches the alarmRisingThreshold.

This object may not be modified if the associated alarmStatus object is equal to valid(1).

alarmRisingEventIndex The index of the eventEntry that is used when a rising threshold is crossed. The eventEntry identified by a particular value of this index is the same as identified by the same value of the eventIndex object. If there is no corresponding entry in the eventTable, then no association exists. In particular, if this value is zero, no associated event will be generated, as zero is not a valid event index.

This object may not be modified if the associated alarmStatus object is equal to valid(1).

alarmFallingEventIndex The index of the eventEntry that is used when a falling threshold is crossed. The eventEntry identified by a particular value of this index is the same as identified by the same value of the eventIndex object. If there is no corresponding entry in the eventTable, then no association exists. In particular, if this value is zero, no associated event will be generated, as zero is not a valid event index.

This object may not be modified if the associated alarmStatus object is equal to valid(1).

alarmOwner The entity that configured this entry and is therefore using the resources assigned to it.
alarmStatus The status of this alarm entry.

 

Event Table

UP_ARROW138B.GIF (883 bytes)
Implementation of the Event group is optional.

The Event group controls the generation and notification of events from this device. Each entry in the eventTable describes the parameters of the event that can be triggered. Each event entry is fired by an associated condition located elsewhere in the MIB. An event entry may also be associated with a function elsewhere in the MIB that will be executed when the event is generated. For example, a channel may be turned on or off by the firing of an event.

Each eventEntry may optionally specify that a log entry be created on its behalf whenever the event occurs. Each entry may also specify that notification should occur by way of SNMP trap messages. In this case, the community for the trap message is given in the associated eventCommunity object. The enterprise and specific trap fields of the trap are determined by the condition that triggered the event. Two traps are defined: risingAlarm and fallingAlarm. If the eventTable is triggered by a condition specified elsewhere, the enterprise and specific trap fields must be specified for traps generated for that condition.

Field Descriptions

eventIndex An index that uniquely identifies an entry in the table. Each such entry defines one event that is to be generated when the appropriate conditions occur.
eventDescription A comment describing this event entry.
eventType The type of notification that the probe will make about this event. In the case of log, an entry is made in the log table for each event. In the case of snmp-trap, an SNMP trap is sent to one or more management stations.
eventCommunity If an SNMP trap is to be sent, it will be sent to the SNMP community specified by this octet string. In the future this table will be extended to include the party security mechanism. This object shall be set to a string of length zero if it is intended that that mechanism be used to specify the destination of the trap.
eventLastTime Sent The value of sysUpTime at the time this event entry last generated an event. If this entry has not generated any events, this value will be zero.
eventOwner The entity that configured this entry and is therefore using the resources assigned to it.

If this object contains a string starting with "monitor" and has associated entries in the log table, all connected management stations should retrieve those log entries, as they may have significance to all management stations connected to this device.

eventStatus The status of this event entry.

If this object is not equal to valid(1), all associated log entries shall be deleted by the agent.

 

Log Table  

UP_ARROW138B.GIF (883 bytes)
A list of events that have been logged.

Field Descriptions

logEventIndex The event entry that generated this log entry. The log identified by a particular value of this index is associated with the same eventEntry as identified by the same value of eventIndex.
logIndex An index that uniquely identifies an entry in the log table amongst those generated by the same eventEntries. These indexes are assigned beginning with 1 and increase by one with each new log entry. The association between values of logIndex and logEntries is fixed for the lifetime of each logEntry. The agent may choose to delete the oldest instances of logEntry as required because of lack of memory. It is an implementation-specific matter as to when this deletion may occur.
logTime The value of sysUpTime when this log entry was created.
logDescription An implementation dependent description of the event that activated this log entry.