Definitions of Managed Objects for the SONET/SDH Interface Type
obsoleted by
- rfc-3592 — Definitions of Managed Objects for the Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Interface Type
obsoletes
- rfc-1595 — Definitions of Managed Objects for the SONET/SDH Interface Type
Extracted elements (29)
Because unavailable-time determination requires a 10-second look-back, an agent may implement a 10-element delay line (shift register approach per Appendix A) to pass one-second statistics through before updating counters, instead of performing retroactive adjustments to ES/SES/CV/UAS counters when the unavailability boundary is crossed.
Multiple SES threshold sets (sonetSESthresholdSet) were added because ANSI T1.231-1993, ITU-T G.826-1995, and ANSI T1.231-1997 all specify different SES error count thresholds from each other and from RFC 1595. Rather than mandating one standard, the MIB lets the agent declare which set it uses, with RFC 1595 thresholds as the backward-compatible default when the object is absent.
The formerly read-only objects sonetMediumType, sonetMediumLineCoding, sonetMediumLineType, and sonetMediumCircuitIdentifier were changed to read-write (MAX-ACCESS) in RFC 2558 to support circuit provisioning use cases, while MIN-ACCESS remains read-only for minimal compliance.
The sonetMediumInvalidIntervals object was added to handle proxy agent scenarios where some historical 15-minute intervals have no data. This is distinct from sonetMediumValidIntervals, which reports the maximum interval number for which any data is available rather than a count of fully valid intervals.
SONET and SDH differ in terminology: an STS (SONET) is called an STM (SDH); an SPE and VT are collectively a Virtual Container (VC) in SDH. SONET performance monitoring terminology is defined in ANSI T1.231; equivalent SDH terms are in CCITT G.783. If this document's definitions conflict with T1.231, implementers must follow this document.
This MIB is compliant to SMIv2. A SMIv1-conformant MIB can be produced via translation, but some information will be lost (e.g., Counter64 objects cannot be translated) and machine-readable SMIv2 semantics become textual descriptions in SMIv1. The translated MIB must be semantically equivalent where translation is possible.
When the 10-second window leading to available or unavailable time crosses a 900-second statistics window boundary, the CV, ES, SES, SEFS, and UAS counts for the PREVIOUS interval must be adjusted. Successive GETs of interval objects (e.g., sonetPathIntervalSES) may return differing values if the first GET occurs during the first few seconds of the new window.
A linkDown trap must be sent only after the agent has determined for certain that the unavailable state has been entered, but the timestamp on the trap must reflect the time of the first UAS (i.e., 10 seconds earlier). A linkUp trap must be handled similarly.
Each interval table includes a TruthValue object (e.g., sonetSectionIntervalValidData) indicating whether data for that interval is valid in the sense intended by ANSI T1.231 clause 9.1.2.2. This flag was added in RFC 2558 to all seven interval tables (Section, Line, Far End Line, Path, Far End Path, VT, Far End VT).
For SONET/SDH Path interfaces, ifOperStatus must assume the value down(2) if sonetPathCurrentStatus has any value other than sonetPathNoDefect(1). ifConnectorPresent must be set to false(2) and ifLinkUpDownTrapEnable defaults to disabled(2).
For SONET/SDH VT/VC interfaces, ifOperStatus must assume the value down(2) if sonetVTCurrentStatus has any value other than sonetVTNoDefect(1). ifConnectorPresent must be set to false(2) and ifLinkUpDownTrapEnable defaults to disabled(2).
For the combined Medium/Section/Line layer, ifOperStatus must assume the value down(2) if sonetSectionCurrentStatus or sonetLineCurrentStatus has any value other than sonetSectionNoDefect(1) and sonetLineNoDefect(1) respectively. ifLinkUpDownTrapEnable defaults to enabled(1).
If a manager changes the value of sonetSESthresholdSet, then the SES statistics collected prior to this change must be invalidated. A SONET/SDH interface must support at least 4 completed 15-minute intervals; the default is 32 and the maximum is 96.
SONET/SDH interfaces must be represented in the ifTable using ifType values sonet(39) for the combined Medium/Section/Line layer, sonetPath(50) for Path interfaces, and sonetVT(51) for VT/VC interfaces. The ifStackTable must be used to maintain the exact configuration and multiplexing relationships between layers.
Coding Violations (CV) are BIP errors in the incoming signal: Section CVs use BIP-8 in byte B1; Line CVs use BIP-8s in B2 bytes (up to 8×N per STS-N frame); Path CVs use BIP-8 in byte B3; VT CVs use BIP-2 in the V5 overhead byte. Each BIP error increments the CV counter independently.
Far End Line and Far End Path statistics (ES, SES, CV, UAS) are derived from the Far End Block Error (FEBE) count: for Line, from the third Z2 byte of Line Overhead; for Path, from the FEBE bits in the G1 byte of Path Overhead. These groups are optional and apply only to LTE equipment providing FEBE information.
Line AIS defect is detected as a '111' pattern in bits 6, 7, 8 of the K2 byte in 5 consecutive frames; terminated when that pattern is absent for 5 consecutive frames. Line AIS failure is declared when defect persists 20.5 ±0.5 s; cleared after 10 ±0.5 s absence.
sonetMediumTable contains per-interface configuration: sonetMediumType (sonet/sdh), sonetMediumLineCoding (B3ZS, CMI, NRZ, RZ), sonetMediumLineType (short/long single-mode, multi-mode, coax, UTP), sonetMediumCircuitIdentifier (DisplayString, SIZE 0..255), and sonetMediumLoopbackConfig (BITS: noLoop, facilityLoop, terminalLoop, otherLoop).
sonetPathCurrentStatus is an Integer32 bitmap (range 1..62): bit 1=sonetPathNoDefect, 2=sonetPathSTSLOP, 4=sonetPathSTSAIS, 8=sonetPathSTSRDI, 16=sonetPathUnequipped, 32=sonetPathSignalLabelMismatch. sonetPathCurrentWidth identifies path type: sts1(1) through sts48cSTM16(5).
sonetSectionCurrentStatus is an Integer32 bitmap representing simultaneous defects: bit 1=sonetSectionNoDefect (set iff no other flag), bit 2=sonetSectionLOS, bit 4=sonetSectionLOF. sonetLineCurrentStatus adds bits: 1=NoDefect, 2=LineAIS, 4=LineRDI.
sonetSESthresholdSet is an enumerated object selecting which SES threshold specification applies: other(1), Bellcore1991(2), ansi1993(3), itu1995(4), or ansi1997(5). If not implemented, the RFC 1595 thresholds (Appendix B) are assumed. Changing this value invalidates all previously collected SES statistics.
sonetVTCurrentStatus is an Integer32 bitmap (range 1..126): bit 1=sonetVTNoDefect, 2=sonetVTLOP, 4=sonetVTPathAIS, 8=sonetVTPathRDI, 16=sonetVTPathRFI, 32=sonetVTUnequipped, 64=sonetVTSignalLabelMismatch. sonetVTCurrentWidth covers VT1.5/VC11, VT2/VC12, VT3, VT6/VC2, and VT6c.
STS-Path RDI must be generated within 100 ms by the STS PTE upon detection of AIS or LOP defect, and transmission must cease within 100 ms when those defects are no longer detected. STS-Path RDI is detected as a '1' in bit 5 of the G1 byte for x consecutive frames (x=5 or x=10 per referenced standard).
The SONET-MIB is organized into eight groups indexed by ifIndex: Medium, Section, Line, Far End Line, Path, Far End Path, VT, and Far End VT. Each group has a Current table (current 15-minute interval) and an Interval table (up to 96 previous 15-minute intervals). The MIB OID root is transmission(39).
Several objects in this MIB have MAX-ACCESS read-write, including sonetMediumLoopbackConfig, sonetMediumType, sonetMediumLineCoding, sonetMediumLineType, sonetMediumCircuitIdentifier, sonetPathCurrentWidth, sonetVTCurrentWidth, and sonetSESthresholdSet. Unauthorized SNMP write access to these objects could disrupt SONET/SDH interface operation or invalidate performance statistics, so SNMPv3 access controls are recommended.
Loss of Frame (LOF): OOF/SEF defect declared on 4 contiguous errored frame alignment words; terminated on 2 contiguous error-free frames. LOF defect declared when OOF persists ≥3 ms; terminated after 1–3 ms in-frame. LOF failure declared when defect persists 2.5 ±0.5 s; cleared when defect absent 10 ±0.5 s.
Loss of Pointer (LOP) failure is declared when LOP defect (no valid pointer in 8 consecutive frames, or NDF='1001' without concatenation indicator for 8 frames) persists for 2.5 ±0.5 s. LOP defect is terminated when a valid pointer with normal NDF='0110' or valid concatenation indicator is detected for 3 contiguous frames.
Loss of Signal (LOS): defect declared after 2.3–100 µs of no transitions; cleared after 125 µs with no defect. LOS failure declared when defect persists for 2.5 ±0.5 s; cleared after 10 ±0.5 s absence. Declaration of LOS failure clears any existing LOF failure.
Unavailable Seconds (UAS): interface becomes unavailable at the onset of 10 contiguous SESs (the 10 SESs are included in unavailable time). Interface becomes available at the onset of 10 contiguous non-SES seconds (those 10 seconds are excluded from unavailable time). While unavailable, only UAS counters are incremented.