Transport Performance Metrics MIB
Extracted elements (25)
The statistics structure is designed so that adjacent report intervals can be combined by simple addition rules (S(N), S(S(X)), MAX(Xmax), MIN(Xmin), and a positional correction term for S(I·X)), allowing a management station to merge two 30-second reports into a 60-second report without re-processing raw data.
The tpmMetricDefTable allows metrics to be defined by reference to external IETF, ITU, or enterprise standards rather than embedding metric semantics in the MIB itself. The tpmMetricDefGlobalID object points to the IPPM-REGISTRY-MIB OID (RFC4148) for IPPM-defined metrics; metrics without a registered OID use the value 0.0.
TPM-MIB is explicitly designed as a drill-down extension to APM-MIB (RFC3729), monitoring sub-application transaction flows not perceived by the end user. For example, APM-MIB reports overall web-browser response time while TPM-MIB separately tracks DNS, TCP-connect, and individual HTTP GET sub-transactions within the same application.
TPM-MIB uses a statistical summation approach—agent collects N, S(X), S(X²), Xmax, Xmin, and S(I·X)—rather than frequency-distribution buckets, because storing raw data or pre-computing floating-point statistics is impractical at thousands of transactions per second. The management station performs final computations from these scalable integer accumulations.
The tpmCurReportTable index order is (application, transaction-metric, network-layer, server-address, client-ID), placing application before network layer—opposite to the RMON2-MIB convention. This means report entries sort by application first, server second, and client third.
TPM-MIB imports AppLocalIndex, TransactionAggregationType, RmonClientID, DataSourceOrZero, and apmExceptionIndex from APM-MIB (RFC3729). When tpmAggrReportCntrlApmCntrlIndex is non-zero, the TPM control entry mirrors all corresponding APM-MIB report-control values, creating a synchronized drill-down relationship between the two MIBs.
If tpmAggrReportCntrlStatus is not active(1), all associated entries in tpmAggrReportTable shall be deleted. Once set to active(1), no objects in tpmAggrReportCntrlTable may be changed.
Implementations must populate tpmTransMetricDirTable with all possible (application, protocol-transaction, metric) combinations at boot and must set the default tpmTransMetricDirConfig to supportedOff(2). The table does not support row creation by management applications.
Implementations should, at a minimum, support a round-trip delay metric and a round-trip loss metric, even though no specific metric is mandatory.
The tpmMetricDefReference object must support an HTTP URL type for referencing the defining standards document online; it may also support other de-referencable URL types such as FTP.
The value of tpmTransMetricDirConfig must persist across reboots, preserving monitoring configuration across device restarts without management-station intervention.
When tpmAggrReportCntrlApmCntrlIndex is non-zero, the agent MUST respond to any SET targeting a row object in that entry as if the object had MAX-ACCESS of read-only, because all parameters are governed by the corresponding APM-MIB control row.
When tpmTransMetricDirConfig transitions from supportedOn(3) to supportedOff(2), the probe shall delete all entries in the tpmReportGroup tables for all studies configured in tpmAggrReportCntrlTable that use this metric-protocol combination.
The tpmAggrReportCntrlTable controls aggregate transport performance studies, specifying data source, aggregation type (flows/clients/servers/applications), report interval, requested and granted table sizes, and number of saved reports. Unlike typical RMON control/data pairs, one entry enables multiple per-interval report snapshots rather than a single data table. Control entries persist across reboots.
The tpmAggrReportTable stores completed transport performance studies, indexed by control entry, report sequence number, application, transaction-metric pair, network-layer protocol, server address, and client ID. Statistical columns cover N, SumX, Maximum, Minimum, SumSq, SumIX, and SumIXSq, each with a ZeroBasedCounter32 base, an overflow counter, and a ZeroBasedCounter64 high-capacity variant.
The tpmCurReportTable provides a real-time snapshot of in-progress and recently completed sub-application transactions. Each entry records a single metric value (tpmCurReportMetricValue) and a completion status (current or completed), making transaction state visible to management applications even while it spans a report boundary.
The tpmExcpReportTable links immediate exception notifications to transactions that exceed thresholds defined in the APM-MIB apmExceptionGroup (RFC3729), reporting aggregated sub-application-level measurements for those applications that breach configured performance thresholds.
The tpmMetricDefTable catalogs all performance metrics available to the agent. Each entry carries a type (other, connectMetric, delayMetric, lossMetric), directional classification (oneWay, twoWay, multiWay), a textual name, a de-referencable URL to the defining document, and an OBJECT IDENTIFIER cross-referencing the IPPM-REGISTRY-MIB.
The tpmTransMetricDirConfig object has three states: notSupported(1) (agent cannot perform the metric due to other configuration constraints), supportedOff(2) (capable but disabled; the boot default for all entries), and supportedOn(3) (actively computing and collecting the metric-protocol-application combination for all interfaces).
The tpmTransMetricDirTable links sets of performance metrics and protocol transactions to application directory entries, enumerating every (application, protocol-transaction, metric) combination the agent can collect. The table is pre-populated at boot and does not support runtime row creation by management applications.
Three clock capability scalars—tpmClockResolution (in microseconds, from SspmMicroSeconds), tpmClockMaxSkew (maximum offset over 86400 seconds, from SspmClockMaxSkew), and tpmClockSource (from SspmClockSource)—expose the timing accuracy of the monitoring agent. All three types are imported from SSPM-MIB (RFC4149).
This document registers the TPM-MIB MODULE-IDENTITY under the RMON subtree as OID { rmon 30 }, assigning tpmCapabilities to { tpmMIB 1 }, tpmReports to { tpmMIB 2 }, and tpmConformance to { tpmMIB 3 }.
TPM-MIB defines read-write objects in tpmAggrReportCntrlTable and tpmTransMetricDirTable that control which metrics are collected, resource allocation, and data-source targeting. Unauthorized writes to these objects could disable monitoring, exhaust agent memory, or redirect data collection. Implementations should enforce SNMPv3 authentication and privacy (authPriv security level) to protect access to these writable objects.
All statistical metric accumulators use a three-tier counter pattern: a ZeroBasedCounter32 base field, a companion ZeroBasedCounter32 overflow counter (instantiated only when the HC object is present), and a ZeroBasedCounter64 high-capacity object (instantiated only when the agent supports high-capacity monitoring for a given dataSource).
tpmAggrReportServerAddress and tpmCurReportServerAddress are encoded as OCTET STRING (SIZE 0..108): a leading length octet identifies the address family size, followed by the address bytes in network byte order. For IPv4, the length octet is 4 followed by four address octets. A length octet of 0 encodes a null address used when aggregation type is application(4) or client(2).