Definitions of Managed Objects for High Bit-Rate DSL - 2nd generation (HDSL2) and Single-Pair High-Speed Digital Subscriber Line (SHDSL) Lines
obsoletes
- rfc-3276 — Definitions of Managed Objects for High Bit-Rate DSL - 2nd generation (HDSL2) and Single-Pair High-Speed Digital Subscriber Line (SHDSL) Lines Processing
Extracted elements (26)
Invalid interval buckets result in holes in interval tables rather than marking entries invalid (unlike RFC 3593 and RFC 2662). A GetNext on a valid interval skips over any invalid preceding interval numbers silently.
Profile-based provisioning was adopted because managed nodes can handle hundreds or thousands of lines and most are provisioned identically. Profiles allow a single parameter set to be shared across multiple lines; individual endpoints can override the span-level profile as needed.
SNR Margin and Loop Attenuation alarms are modeled per-endpoint in the MIB, whereas the EOC specification treats them per-unit. For repeaters this imposes variance requiring the terminal unit agent to detect threshold crossings, but impact is minimal since alarm state is reported in the same EOC message as current SNR/attenuation values.
The MIB module is designed to require no management communication between modems beyond what is inherent in the EOC line protocol (ANSI T1E1.4 for HDSL2, ITU G.991.2 for SHDSL), allowing an agent to reside at either end of the line.
RFC 4319 obsoletes RFC 3276, extending support from G.shdsl to G.shdsl.bis. Key additions are a 3rd and 4th wire pair, payload-only rate objects, tip/ring reversal indication, wire pair activation state, and relaxed rate constraints (now only bounded by Unsigned32).
All MIB tables indexed by ifIndex MUST be maintained in a persistent manner, including hdsl2ShdslSpanConfTable, hdsl2ShdslEndpointConfTable, hdsl2ShdslEndpointCurrTable, hdsl2ShdslUnitMaintTable, and both profile tables.
An active span configuration profile entry MUST remain active until all references to it are removed. A profile with active references MUST NOT be deleted.
Any attempt to set hdsl2ShdslSpanConfProfile, hdsl2ShdslSpanConfAlarmProfile, or hdsl2ShdslEndpointAlarmConfProfile to a value that is not the index of an active entry in the respective profile table MUST be rejected.
Implementations MUST provide a default profile named 'DEFVAL' for each profile type. Before lines are explicitly configured, 'DEFVAL' is automatically used. HDSL2 lines MUST reference the 'DEFVAL' span profile since span configuration profiles only apply to SHDSL.
Only one threshold notification SHOULD be sent per 15-minute interval per interface. Non-threshold notifications SHOULD be rate limited with at least a 1-minute gap between consecutive same-event notifications; rate-limited notifications are dropped and not queued.
Profile changes MUST take effect immediately and MAY result in a hard reset or soft restart of units on the line. A profile MUST be unreferenced from all lines before it can be deleted or taken out of service.
The ifFixedLengthGroup from RFC 2863 MUST be supported for HDSL2/SHDSL interfaces; the ifRcvAddressGroup does not apply. ifPhysAddress MUST contain a zero-length octet string.
When interval data is suspect or known to be invalid, the agent MUST NOT report the interval. If the current 15-minute event bucket is determined to be invalid, notifications based upon its value MUST NOT be generated. This results in holes in interval tables.
Performance counters are maintained at three granularities per segment endpoint: cumulative since last xU restart (ES, SES, CRCanomalies, LOSWS, UAS), current and up to 96 historical 15-minute intervals, and current and up to 30 historical 1-day intervals. Counters are reset only on agent reset, not xU reinitialization.
Sixteen SNMP notifications are defined including threshold crossings for ES, SES, CRCanomalies, LOSWS, UAS, SNR margin, and loop attenuation, plus operational notifications for loopback failure, power backoff, device fault, DC continuity fault, config/protocol init failure, missing neighbor, invalid repeater count, and local power loss.
The Hdsl2ShdslClockReferenceType enumeration defines four STU-C clock reference modes: localClk(1) (G.991.2 Mode-1), networkClk(2) (Mode-2), dataOrNetworkClk(3) (Mode-3a), and dataClk(4) (Mode-3b).
The hdsl2ShdslEndpointCurrStatus BITS object is an 11-bit bitmask covering noDefect(0), powerBackoff(1), deviceFault(2), dcContinuityFault(3), snrMarginAlarm(4), loopAttenuationAlarm(5), loswFailureAlarm(6), configInitFailure(7), protocolInitFailure(8), noNeighborPresent(9), and loopbackActive(10). There is a 1:1 relationship between status bits and notification thresholds.
The hdsl2ShdslEndpointMaintTable supports per-endpoint maintenance operations: loopback configuration (noLoopback/normalLoopback/specialLoopback), tip/ring reversal state, power backoff mode (default/enhanced), and soft restart (agent executes restart after approximately 5 seconds then restores object to ready(1)).
The Hdsl2ShdslTransmissionModeType BITS construct encodes regional PSD settings: bit 0 (region1) indicates ITU-T G.991.2 Annex A, bit 1 (region2) indicates ITU-T G.991.2 Annex B.
The Hdsl2ShdslUnitId textual convention identifies each unit in an HDSL2/SHDSL span using EOC addressing: xtuC(1) for the CO terminal unit, xtuR(2) for the CPE terminal unit, and xru1(3) through xru8(10) for up to eight regenerators numbered from the CO side.
The Hdsl2ShdslWirePair textual convention defines wirePair1(1) through wirePair4(4). HDSL2 supports only wirePair1 (two-wire); SHDSL adds optional wirePair2 (four-wire); G.shdsl.bis further adds wirePair3 (six-wire) and wirePair4 (eight-wire).
Two new payload-rate objects (hdsl2ShdslStatusMaxAttainablePayloadRate and hdsl2ShdslStatusActualPayloadRate) are added in RFC 4319 to report rates excluding framing overhead, complementing the existing line-rate objects that include framing.
The HDSL2-SHDSL-LINE-MIB MODULE-IDENTITY is assigned OID { transmission 48 } by IANA, allocated when RFC 3276 was published. IANA also previously assigned ifTypes hdsl2(168) and shdsl(169). RFC 4319 requires no new IANA action.
Several read-write and read-create objects in this MIB can disrupt HDSL2/SHDSL service if manipulated without authorization, including loopback activation, soft restart, power backoff configuration, and profile changes that may trigger line reinitialization. Implementations should employ SNMPv3 authentication and access control to restrict write access to these objects.
The hdsl2ShdslEndpointCurrActivationState object tracks wire pair activation with three states: preActivation(1) (PreTrain), activation(2) (Training), and data(3) (Trained), per the ITU-T G.991.2 Section 6.2 PMD Activation Sequence.
The G.991.2 Inventory Response (Message ID 130) carries vendor fields at fixed offsets: Vendor ID octets 25-32 (8 bytes), model number octets 33-44 (12 bytes), serial number octets 45-56 (12 bytes), list number octets 3-5 (3 bytes), issue number octets 6-7 (2 bytes), software version octets 8-13 (6 bytes), equipment code octets 14-23 (10 bytes, ANSI T1.213), and other vendor info octets 57-68 (12 bytes).