Definitions of Managed Objects for the DS1, E1, DS2, and E2 Interface Types
obsoleted by
- rfc-4805 — Definitions of Managed Objects for the DS1, J1, E1, DS2, and E2 Interface Types
obsoletes
- rfc-2495 — Definitions of Managed Objects for the DS1, E1, DS2 and E2 Interface Types
Extracted elements (25)
DS1 and E1 line disciplines are similar enough that separate MIBs are unwarranted—Loss of Frame is defined in both ESF and D4 specs, and other performance parameters overlap substantially. Consequently, e1(19) and g703at2mb(67) ifTypes are obsoleted; ds1(18) covers all variants.
dsx1LoopbackConfig represents the desired loopback state (manager-controlled) while dsx1LoopbackStatus reflects the actual state including far-end-initiated loopbacks. This separation allows a management entity to distinguish manager-requested versus remotely-imposed loopback conditions.
ifStackTable replaces the deprecated dsx1IfIndex for expressing CSU/DSU proxy relationships between paired DS1 interfaces. The ifStackTable is consistent with sub-layer associations and allows proper integration with ifStackTable-aware management tools.
Performance statistics use Gauge32 (PerfCurrentCount/PerfIntervalCount/PerfTotalCount) rather than Counter32 because UAS boundary crossing can cause ES, BES, SES, and SEFS values to decrease retroactively when the 10-second determination window is applied. A monotonically increasing counter type would be semantically incorrect.
The MIB design closely aligns with the set of objects that can generally be read from currently deployed DS1/E1/DS2/E2 devices rather than supporting all theoretically possible management operations (e.g., multiplexor management). J2 interfaces are explicitly excluded.
All DS1, E1, DS2, and E2 interfaces use ifType ds1(18). DS2 or E2 versus DS1/E1 is distinguished by examining ifSpeed (6312000 for DS2, 8448000 for E2) or dsx1LineType rather than a separate ifType value. It is not always necessary or desirable to represent DS2 interfaces explicitly in the ifTable.
In proxy scenarios where the agent does not communicate continuously with DS1/E1 devices, missed collection periods result in invalid interval data. dsx1InvalidIntervals counts gaps within the valid range; dsx1IntervalValidData per row flags individual invalid intervals, which count as 0 in 24-hour totals.
A linkDown trap SHALL be sent only after the agent has determined for certain that the unavailable state has been entered, but the timestamp on the trap SHALL be that of the first UAS (10 seconds earlier). A linkUp trap is handled similarly.
Agents supporting read/write access to dsx1LoopbackConfig MUST return inconsistentValue in response to a requested loopback state that the interface does not support.
dsx1LineStatusChangeTrapEnable defaults to disabled(2). Agents generate dsx1LineStatusChange traps only when explicitly enabled per-interface. The dsx1LineIndex object SHOULD be made equal to ifIndex to allow proper use of ifStackTable.
Performance parameters MUST be accumulated in 15-minute intervals; up to 96 intervals (24 hours) MUST be retained. A rolling 24-hour total MUST also be maintained. Performance collection continues even when the interface is operationally down.
The far end cannot undo loopbacks set by a manager; a manager can undo loopbacks set by the far end. A LineLoopback request from the far end is incremental to an existing InwardLoopback established by a manager; when far-end sends NoLoopback, the InwardLoopback remains.
Unavailable Seconds (UAS) counting begins at the onset of 10 contiguous Severely Errored Seconds (SESs). While unavailable, only the UAS counter increments; ES, BES, SES, SEFS, PCV, and DM counters are frozen. The interface returns to available at the onset of 10 contiguous non-SES seconds.
dsx1ChanMappingTable maps DS1 or DS2 channel numbers within a parent DS3/E3 or DS2/E2 to their ifIndex values. Enables navigation of hierarchical channelization (DS3->DS2->DS1->DS0) using a common lookup mechanism.
dsx1ConfigTable is the primary per-interface configuration table, indexed by dsx1LineIndex (which SHOULD equal ifIndex). It contains 22 objects covering line type, coding, loopback config/status, signal mode, transmit clock source, channelization, FDL usage, circuit identifier, and line build-out.
dsx1CurrentTable accumulates near-end performance statistics for the current 15-minute interval: Errored Seconds (ESs), Severely Errored Seconds (SESs), Severely Errored Framing Seconds (SEFSs), Unavailable Seconds (UASs), Controlled Slip Seconds (CSSs), Path Coding Violations (PCVs), Line Errored Seconds (LESs), Bursty Errored Seconds (BESs), Degraded Minutes (DMs), and Line Code Violations (LCVs). All counters use PerfCurrentCount (Gauge32).
dsx1IntervalTable stores the same ten performance counters for each of the previous 96 completed 15-minute intervals, indexed by (dsx1IntervalIndex, dsx1IntervalNumber) where 1 is the most recent. A dsx1IntervalValidData boolean flags intervals where proxy data was unavailable.
dsx1LineCoding enumerates zero-code suppression schemes: JBZS (forces pulse in bit 8, leaving 1.344Mbps for data), B8ZS (replaces 8 zeros with bipolar violations pattern), HDB3 (for E1), ZBTSI (ANSI clear channel), AMI (no suppression, higher layer responsible), and B6ZS (for DS2, replaces 6-zero sequences).
dsx1LineStatus is a read-only bitmap (INTEGER 1..131071) representing simultaneous line alarms and loopback state. Seventeen bit positions are defined: NoAlarm(1), RcvFarEndLOF(2), XmtFarEndLOF(4), RcvAIS(8), XmtAIS(16), LossOfFrame(32), LossOfSignal(64), LoopbackState(128), T16AIS(256), and DS2-specific conditions up to bit 65536.
dsx1LineType enumerates 13 framing formats: dsx1ESF, dsx1D4, dsx1E1, dsx1E1CRC, dsx1E1MF, dsx1E1CRCMF, dsx1Unframed, dsx1E1Unframed, dsx1DS2M12, dsx1E2, dsx1E1Q50, dsx1E1Q50CRC, and other. The selected type determines capacity (e.g., E1MF yields 30x64k=1920k due to signaling overhead) and error statistic interpretation.
dsx1LoopbackStatus is a read-only bitmap (INTEGER 1..127) indicating currently active loopbacks and their source (manager or far end). Seven bit positions: NoLoopback(1), NearEndPayloadLoopback(2), NearEndLineLoopback(4), NearEndOtherLoopback(8), NearEndInwardLoopback(16), FarEndPayloadLoopback(32), FarEndLineLoopback(64).
dsx1TotalTable provides cumulative 24-hour totals for all ten performance parameters. Invalid 15-minute intervals (flagged by dsx1IntervalValidData=false) contribute 0 to these totals.
The DS1-MIB module (OID transmission 18) defines managed objects for DS1, E1, DS2, and E2 interfaces. It subsumes the obsoleted e1(19) and g703at2mb(67) ifTypes, and obsoletes RFC 2495.
Several read-write objects in the DS1-MIB can disrupt service if accessed by unauthorized parties: dsx1LoopbackConfig (can place the line in loopback, effectively taking it out of service), dsx1SendCode (can inject test patterns), and dsx1Channelization (can destroy DS0 ifTable entries). SNMPv3 with authentication and privacy is recommended to protect these objects.
DS1 Available/Unavailable state machine: transitions to Unavailable at the onset of 10 contiguous SESs or a failure condition. Transitions back to Available at the onset of 10 contiguous non-SES seconds. When the 10-second determination window crosses a 900-second statistics boundary, counts in the previous interval must be retroactively adjusted (or a 10-second delay pipeline used).