High Capacity Textual Conventions for MIB Modules Using Performance History Based on 15 Minute Intervals
Extracted elements (15)
64-bit versions of the RFC 3593 textual conventions are needed but SMIv2 provides no Gauge64 or Unsigned64 type. CounterBasedGauge64 from RFC 2856 cannot be used as a base type for TCs either, so the conventions are defined directly on Counter64, inheriting its read-only access and other constraints.
The three Counter64-based count TCs (HCPerfCurrentCount, HCPerfIntervalCount, HCPerfTotalCount) are explicitly described as a limited, short-term solution that may be deprecated once a long-term replacement is defined and deployed.
HCPerfCurrentCount, HCPerfIntervalCount, and HCPerfTotalCount are not strictly supported in SMIv2 because they use Counter64 syntax without preserving its 'always increasing' and 'counter wrap' semantics. Management applications that rely solely on the Counter64 ASN.1 tag may misinterpret these objects as standard counters.
No sub-range can be specified and no DEFVAL clause can be used in object definitions based on these textual conventions, because Counter64 does not permit sub-ranges or DEFVALs. Objects of these types also cannot appear in an INDEX clause.
Objects defined using the HC-PerfHist textual conventions MUST have MAX-ACCESS read-only, because the underlying Counter64 base type is read-only.
Use of these textual conventions assumes the agent supports 15-minute based history counters and is capable of keeping a history of 96 intervals of 15-minute performance data.
When an agent has no valid data for the current or a historical interval, the corresponding object instance MUST NOT be available; a retrieval request SHALL return an error indicating the instance does not exist.
HCPerfCurrentCount is a Counter64-based gauge for a performance measurement in the current 15-minute interval. Starts at zero, increments on events, is stored as X(1) at interval end and reset. If no valid data is available, the object instance is absent and a retrieval returns an error.
HCPerfIntervalCount is a Counter64-based gauge representing a previous 15-minute measurement interval. At each interval boundary: X(n) is discarded, X(i) takes X(i-1) for n>=i>1, X(1) takes the prior current value Y, and aggregate Z is adjusted if supported.
HCPerfIntervalThreshold defines a fault threshold alarm control range for 15-minute intervals. Range is Unsigned32 (0..900), where 0 disables the alarm.
HCPerfInvalidIntervals represents the number of near-end 15-minute intervals for which no data is available, typically zero except in proxy situations. Encoded as Integer32 (0..96).
HCPerfTimeElapsed represents seconds elapsed since the beginning of the current measurement period. For 15-minute intervals the range is (0..899); for 24-hour intervals (0..86399). Capped at maximum value if the interval is extended by clock adjustments or leap seconds. Encoded as Integer32 (0..86399).
HCPerfTotalCount is a Counter64-based gauge representing the aggregate of all previous valid 15-minute intervals; intervals with no valid data are excluded. Value saturates at 2^64-1 and may decrease if a retroactive adjustment causes the underlying count to fall below that ceiling.
HCPerfValidIntervals is a textual convention representing the count of near-end 15-minute intervals for which data was collected. Its value is 96 unless measurement started within the last 1440 minutes; encoded as Integer32 (0..96).
The HC-PerfHist-TC-MIB module defines only textual conventions and no management objects. Meaningful security considerations apply only to the MIB modules that use these conventions to define objects; this document itself has no direct impact on Internet security.