Textual Conventions for MIB Modules Using Performance History Based on 15 Minute Intervals
obsoleted by
- rfc-3593 — Textual Conventions for MIB Modules Using Performance History Based on 15 Minute Intervals
Extracted elements (14)
Telecommunications equipment commonly uses 15-minute interval buckets for performance history (aligned to ANSI T1.231 wall-clock boundaries), rather than continuous counters polled by the manager. This memo standardizes TCs for that pattern rather than comparing strategies.
The document defines Textual Conventions rather than object types so that MIB modules requiring 15-minute performance history data share consistent semantics. This follows the RFC 1903 Textual Conventions mechanism, improving human readability and semantic precision over raw SMI types.
If a system's time-of-day clock is adjusted (e.g., set back to correct drift), xyzTimeElapsed may transiently exceed its defined maximum of 899 seconds. Agents should return the maximum value (899) in this case rather than an error, per the ANSI T1.231 procedure of ending intervals at 15-minute wall-clock boundaries.
In proxy deployments (e.g., for DS3/E3 interfaces), periods of lost communication between proxy and managed device may result in some 15-minute intervals being unavailable. xyzValidIntervals in such cases reflects the maximum interval number with available data, not a contiguous range.
The number of 15-minute history intervals n supported by an agent must satisfy 0 < n ≤ 96. Any additional constraints on n must be defined in the DESCRIPTION clause of the specific MIB module.
When an agent has no valid data for a particular history interval, the corresponding PerfIntervalCount object instance is not available; a retrieval request must return a noSuchName error (SNMPv1) or noSuchInstance error (SNMPv2 GET).
PerfCurrentCount is a Textual Convention (Gauge32) representing a counter for performance measurements in the current 15-minute interval. The counter starts at zero, increments as events occur, and is stored into the first history interval at interval end, then restarted at zero.
PerfIntervalCount is a Textual Convention (Gauge32) representing a counter for performance measurements in a previous 15-minute interval. At the end of each interval, IntervalCount(n) is discarded, values shift (IntervalCount(i) = IntervalCount(i-1)), and IntervalCount(1) receives the CurrentCount value.
PerfTotalCount is a Textual Convention (Gauge32) representing an aggregate counter over all previous valid 15-minute measurement intervals. Intervals for which no valid data was available are excluded from the aggregate.
xyzInvalidIntervals is a read-only INTEGER (0..n) indicating the number of intervals in the range 0 to xyzValidIntervals for which no data is available. Typically zero except in proxy situations where some interval data is unavailable.
xyzTimeElapsed is a read-only INTEGER (0..899) indicating the number of seconds elapsed since the beginning of the current 15-minute measurement period. If the current interval exceeds the maximum due to clock adjustments, the agent returns the maximum value of 899.
xyzValidIntervals is a read-only INTEGER (0..n, where 1 ≤ n ≤ 96) indicating the number of previous near-end intervals for which data was collected. In proxy situations, this reflects the maximum interval number for which data is available, not necessarily all intervals up to n.
This document defines the PerfHist-TC-MIB MODULE-IDENTITY assigned under mib-2 58 (OID { mib-2 58 }), providing the Textual Conventions PerfCurrentCount, PerfIntervalCount, and PerfTotalCount.
This memo defines only textual conventions for use in other MIB modules; security issues for those MIB modules are addressed in the memos that define them. No independent security considerations are introduced by this document.