Definitions of Managed Objects for the SONET/SDH Interface Type
obsoleted by
- rfc-2558 — Definitions of Managed Objects for the SONET/SDH Interface Type
Extracted elements (29)
The sonetMediumTable covers both optical and electrical SONET/SDH interfaces. Electrical SONET uses B3ZS or CMI line coding (STS-1 and STS-3), while optical SONET uses NRZ or RZ; this distinction is captured in sonetMediumLineCoding to support management of heterogeneous physical media.
The UAS counter adjustment required when a 10-or-more-second SES/UAS boundary period crosses a 900-second statistics window causes successive GETs of sonetPathIntervalSES and sonetPathIntervalUAS to return differing values. This is acknowledged as 'an unavoidable side-effect of selecting the presently defined managed objects as a basis for this memo.'
SONET and SDH use different terminology for equivalent concepts: SONET SPE/VT corresponds to SDH Virtual Container (VC), and SONET STS corresponds to SDH STM. sonetMediumType distinguishes sonet(1) from sdh(2). SDH Performance Monitoring definitions follow CCITT G.783 and differ from but are analogous to the SONET definitions given in this document.
This MIB specifies objects in a manner compliant with the SNMPv2 SMI (RFC 1442) while remaining semantically identical to the peer SNMPv1 definitions, enabling use with both SNMPv1 and SNMPv2 management protocols.
A SONET device must support at least n=4 completed 15-minute intervals of performance data; the default is 32 intervals and the maximum is 96 (covering up to 24 hours). sonetMediumValidIntervals reports how many valid intervals are currently stored.
ifOperStatus for a SONET/SDH Medium/Section/Line interface MUST assume the value down(2) if sonetSectionCurrentStatus or sonetLineCurrentStatus has any value other than sonetSectionNoDefect(1) or sonetLineNoDefect(1), respectively.
ifOperStatus for a SONET/SDH Path interface MUST assume down(2) if sonetPathCurrentStatus has any value other than sonetPathNoDefect(1); similarly for VT interfaces using sonetVTCurrentStatus.
The ifType for the combined SONET/SDH Medium/Section/Line layer MUST be sonet(39); SONET/SDH Paths MUST use sonetPath(50); and SONET/SDH VTs/VCs MUST use sonetVT(51).
Coding Violations (CV) count BIP errors per layer: Section CVs use BIP-8 in B1 byte; Line CVs use BIP-8 in each B2 byte (up to 8×N per STS-N frame); Path CVs use BIP-8 in B3 byte of STS SPE; VT CVs use BIP-2 in V5 overhead byte.
Far End Line and Far End Path groups collect ES, SES, CV, and UAS statistics derived from the far-end block error (FEBE) code: in the Z2 byte of Line Overhead for Line, and in the G1 byte of Path Overhead for Path. Both current (15-minute) and interval (up to 96 × 15 min) tables are defined.
Severely Errored Second (SES) thresholds are rate-dependent: Section SES uses BER threshold ≈1.5×10⁻⁷ (x=9 CVs for OC-1); Line SES uses ≈2×10⁻⁷ (x=12 for OC-1); VT1.5 SES uses x=4 at ≈2×10⁻⁶. Exact x values for OC-1 through OC-48 and VT1.5 through VT6 are tabulated in section 3.6.
SONET/SDH layers are represented as stacked ifEntries: one ifEntry for the combined Medium/Section/Line layer (ifType=sonet(39)), L ifEntries for SONET/SDH Paths (ifType=sonetPath(50)), and K ifEntries for VTs/VCs (ifType=sonetVT(51)). The ifStackTable maintains the exact multiplexing relationships.
sonetLineCurrentStatus is a bit-map sum: bit 1 = sonetLineNoDefect, bit 2 = sonetLineAIS, bit 4 = sonetLineRDI. Multiple defects may be represented simultaneously.
sonetPathCurrentStatus is a bit-map sum: bit 1 = sonetPathNoDefect, bit 2 = sonetPathSTSLOP, bit 4 = sonetPathSTSAIS, bit 8 = sonetPathSTSRDI, bit 16 = sonetPathUnequipped, bit 32 = sonetPathSignalLabelMismatch.
sonetPathCurrentWidth identifies the SONET/SDH Path type: sts1(1)=51.84 Mbps, sts3cSTM1(2), sts12cSTM4(3), sts24c(4), sts48cSTM16(5). This is the only read-write object in the current-statistics tables.
sonetSectionCurrentStatus is a bit-map sum: bit 1 = sonetSectionNoDefect, bit 2 = sonetSectionLOS, bit 4 = sonetSectionLOF. sonetSectionNoDefect MUST be set if and only if no other flag is set.
The SONET-MIB module is rooted at { transmission 39 } and organized into three top-level object identifier branches: sonetObjects (medium/section/line/far-end-line groups), sonetObjectsPath (path/far-end-path groups), and sonetObjectsVT (VT/far-end-VT groups).
Unavailable Seconds (UAS): an interface is unavailable at the onset of 10 contiguous SESs (those 10 SESs are included in unavailable time) and becomes available again at the onset of 10 contiguous non-SES seconds (those 10 seconds are excluded from unavailable time). Only UAS counters are incremented while unavailable; all other counters are incremented only while available.
Unequipped state is signaled by transmitting Path or VT Signal Label as zero: C2 byte of STS Path Overhead = 0x00 for unequipped Path; V5 byte of VT Path Overhead = 0x00 for unequipped VT. Signal Label Mismatch occurs when a received label does not equal the provisioned value or 0x01 ('equipped non-specific').
Section 7 notes that the MIB objects defined are read-only (MAX-ACCESS read-only or not-accessible) with the exception of sonetPathCurrentWidth, which is read-write. The security model relies on the underlying SNMP administrative framework (RFC 1445/RFC 1448) for access control; no SONET-specific security mechanisms are defined.
Line AIS state machine: L-AIS defect is detected as a '111' pattern in bits 6–8 of K2 byte for five consecutive frames, and terminated when that pattern is absent for five consecutive frames. Line AIS failure is declared when the defect persists 20.5±0.5 s and cleared when absent for 10±0.5 s.
Line RDI (FERF) state machine: Line RDI defect is a '110' code in bits 6–8 of K2 in five consecutive frames, terminated when any other code appears for five consecutive frames. Line RFI failure is declared at 2.5±0.5 s and cleared when absent for 10±0.5 s.
LOS state machine: LOS defect is declared when no transitions are detected for 2.3–100 µs and cleared after a 125 µs interval with no LOS. LOS failure is declared when the defect persists 2.5±0.5 s and cleared when absent for 10±0.5 s; LOS failure declaration clears any existing LOF failure.
Section LOF state machine: an OOF/SEF defect is declared on four contiguous errored frame alignment words and cleared on two contiguous error-free frames. LOF defect is declared when OOF/SEF persists for 3 ms and cleared when signal is in-frame for 1–3 ms. LOF failure is declared when LOF defect persists 2.5±0.5 s and cleared when LOF defect is absent for 10±0.5 s.
STS-Path AIS state machine: AIS defect is detected as all-ones in H1 and H2 bytes for three contiguous frames, terminated when a valid STS Pointer is detected (NDF='1001' for one frame or '0110' for three). STS-Path AIS failure is declared at 2.5±0.5 s and cleared when absent for 10±0.5 s.
STS-Path LOP state machine: LOP defect is declared when a valid pointer is not found in eight consecutive frames or NDF='1001' appears for eight consecutive frames without concatenation. LOP defect is terminated on three contiguous frames with a valid pointer (NDF='0110') or concatenation indicator. LOP failure is declared at 2.5±0.5 s persistence and cleared when absent for 10±0.5 s.
STS-Path RDI state machine: RDI is detected as a '1' in bit 5 of the G1 byte for five contiguous frames and removed when a '0' is seen for five contiguous frames. STS-Path RFI failure is declared at 2.5±0.5 s and cleared when absent for 10±0.5 s. An STS PTE must generate RDI within 100 ms of detecting AIS or LOP, and cease within 100 ms when no longer detected.
VT-Path AIS state machine: VT-Path AIS defect is detected as all-ones in V1 and V2 bytes for three contiguous VT superframes; terminated on a valid VT pointer with NDF='1001' for one superframe or '0110' for three. VT-Path AIS failure is declared at 2.5±0.5 s and cleared when absent for 10±0.5 s. Incoming VT-Path AIS shall not cause declaration of a VT LOP defect.
sonetMediumCircuitIdentifier is a DisplayString of SIZE(0..255) containing the transmission vendor's circuit identifier; it is carried in ifPhysAddress as an octet string (zero-length if no identifier assigned).