Textual Conventions for MIB Modules Using Performance History Based on 15 Minute Intervals
obsoletes
- rfc-2493 — Textual Conventions for MIB Modules Using Performance History Based on 15 Minute Intervals
Extracted elements (14)
Performance history textual conventions are based on 32-bit counts (Gauge32). For high-capacity performance history counts, a separate document is referenced, keeping this TC MIB focused on the standard 32-bit case.
The 15-minute interval strategy is common in telecommunications equipment rather than continuous counting. MIB designers should consider trade-offs including polling policy, management traffic, agent simplicity, and data currentness when choosing a history strategy.
If the system's time-of-day clock is adjusted, the current interval may exceed the xyzTimeElapsed maximum of 899 seconds; the agent should return the maximum value in this case. Following ANSI T1.231 boundaries with small, frequent clock adjustments avoids marking intervals invalid.
In proxy scenarios, the proxy may not have up-to-date configuration information and may have missed data collection during periods of no communication with managed devices (e.g., DS3/E3 interfaces), resulting in some intervals being unavailable in the interval table.
The number of history intervals n supported by an agent must satisfy 0 < n ≤ 96; any additional constraints must be defined in the MIB module's DESCRIPTION clause.
When an agent has no valid data for a particular history interval, the corresponding object instance is not available and a retrieval request must return an appropriate error (noSuchName for SNMPv1, noSuchInstance for SNMPv2 GET).
PerfCurrentCount is a Textual Convention (Gauge32) for counters in the current 15-minute measurement interval. The counter starts at zero, increments as events occur, and is stored into the first history interval at interval end, then reset to zero.
PerfIntervalCount is a Textual Convention (Gauge32) for counters associated with a previous 15-minute measurement interval. At interval end, IntervalCount(n) is discarded, each IntervalCount(i) takes the value of IntervalCount(i-1), and IntervalCount(1) takes the value of CurrentCount.
PerfTotalCount is a Textual Convention (Gauge32) aggregating all previous valid 15-minute measurement intervals; intervals with no valid data are excluded from the aggregate.
xyzInvalidIntervals is an INTEGER (0..n) object reporting the number of intervals in the range 0 to xyzValidIntervals for which no data is available, typically zero except in proxy scenarios.
xyzTimeElapsed is an INTEGER (0..899) object indicating the number of seconds elapsed since the beginning of the current measurement period. If the current interval exceeds the maximum due to clock adjustment, the agent returns the maximum value.
xyzValidIntervals is an INTEGER (0..n) object reporting the number of previous near-end intervals for which data was collected, where 1 ≤ n ≤ 96. In proxy situations, it is the maximum interval number for which data is available.
The PerfHist-TC-MIB module is assigned OID { mib-2 58 } and defines the PerfCurrentCount, PerfIntervalCount, and PerfTotalCount textual conventions for use by MIB modules requiring 15-minute performance history.
This memo defines only textual conventions; security issues are deferred to the individual MIB modules that use these conventions, as those modules define the actual managed objects and their access controls.