Definitions of managed objects for the DS1 Interface type
obsoleted by
- rfc-1406 — Definitions of Managed Objects for the DS1 and E1 Interface Types
updated by
- rfc-1239 — Reassignment of experimental MIBs to standard MIBs
Extracted elements (28)
A separate CSUIndex is used instead of ifIndex because multiple bit streams can be multiplexed onto a single DS1 CSU (producing multiple ifIndex values) or multiple CSUs can be concatenated into a single logical interface, making a many-to-one mapping between CSU indices and ifIndex necessary.
T1 and E1 line disciplines are considered similar enough that separate MIBs are unwarranted; a single MIB covers both, though some definitions (e.g., Loss of Frame) are more rigorously defined in the ESF specification than in D4.
The Fractional DS1 group was added to meet a requirement not easily satisfied elsewhere: enabling management of devices that utilize only a subset of the 24 or 32 available 8-bit channels over a managed CSU.
The MIB was intentionally aligned with the AT&T ESF CSU object set to match currently deployed equipment, with simple generalization extending applicability to D4 and G.704 devices. This pragmatic choice drove the selection of statistics objects.
D4 and G.704 (section 2.1.3.2) interfaces do not support Code Violation Error Events; agents for these interface types may treat ds1IntervalCVs, ds1CurrentCVs, and ds1TotalCVs as not-accessible.
For fractional DS1 channel numbering: ESF, D4, and ANSI-ESF use channels 1–24; G.704 uses channels 1–32 with channel 1 as overhead; G.704-CRC uses channels 1–32 with channels 1 and 17 as overhead.
G.704 interfaces do not support Red Alarms; agents managing such interfaces must return ds1NoRedAlarm for the ds1RedAlarm object.
G.704 interfaces do not support Yellow Alarms; agents managing such interfaces must return ds1NoYellowAlarm for the ds1YellowAlarm object.
Some currently deployed CSUs do not record the full set of statistics specified in the Interval, Current, and Total groups; agents queried for these objects may treat them as not-accessible rather than returning zeroes.
When a 10-or-more second Unavailable Signal State transition crosses a 900-second statistics window boundary, successive GETs of ds1IntervalSES and ds1IntervalUAS may return differing values; this is an acknowledged unavoidable side-effect of the AT&T object basis.
Each agent on a host using DS1 physical interfaces is required to assign a small, positive integer (CSUIndex) uniquely to each CSU attached to the node.
Implementation of the DS1 Configuration group (ds1ConfigTable) is mandatory for all systems that attach to a DS1 interface.
Implementation of the DS1 Current group (ds1CurrentTable) is mandatory for all systems that attach to a DS1 interface.
Implementation of the DS1 Fractional group (ds1FracTable) is mandatory for those systems utilizing a fractional DS1 capability.
Implementation of the DS1 Interval group (ds1IntervalTable) is mandatory for all systems that attach to a DS1 interface.
Implementation of the DS1 Total group (ds1TotalTable) is mandatory for all systems that attach to a DS1 interface.
ds1ConfigTable (OID ds1 1) is the DS1 Configuration table indexed by ds1CSUIndex; entries include line type, zero coding, loopback state, send code, alarm status, and circuit identifier. Read-only by default but may be made read-write at agent discretion.
ds1CurrentTable (OID ds1 3) stores error counters for the current 15-minute interval per CSU, with the same seven counter types as the Interval table (ESs, SESs, SEFSs, UASs, CSSs, BPVs, CVs).
ds1FracTable (OID ds1 5) maps DS1 channel numbers (1..32) to ifIndex values for fractional DS1 implementations. When ds1Index in the config table is 0, fractional DS1 is in use and this table provides the per-channel interface bindings.
ds1IntervalTable (OID ds1 2) stores per-CSU error statistics for each of the 96 most recent completed 15-minute intervals, indexed by ds1IntervalIndex and ds1IntervalNumber (1=most recent, 96=least recent). Counters include ESs, SESs, SEFSs, UASs, CSSs, BPVs, and CVs.
ds1LineType enumerates six DS1 line variants: ds1ESF (AT&T Extended SuperFrame), ds1D4 (AT&T D4), ds1ANSI-ESF (ANSI ESF), ds1G704 (G.704 section 2.1.3.2), and ds1G704-CRC (G.704 section 2.1.3.1). The line type affects bit capacity and interpretation of error statistics.
ds1Loopback has five states: ds1NoLoop, ds1LocalLoopbackLocalSide, ds1LocalLoopbackRemoteSide, ds1RemoteLoopbackLocalSide, and ds1RemoteLoopbackRemoteSide. Agents supporting read-write access must return badValue for unsupported loopback states.
ds1SendCode indicates the test signal being transmitted: ds1SendNoCode, ds1SendSetCode (loopback request), ds1SendResetCode (loopback termination), ds1SendQRSS (ANSI T1.403-1989 BERT pattern), or ds1OtherTest (other BERT/BLERT patterns).
ds1TotalTable (OID ds1 4) stores cumulative 24-hour error sums for the period preceding the first valid interval in ds1CurrentTable, using the same seven counter types.
ds1ValidIntervals (INTEGER 0..96) indicates the number of previous 15-minute intervals for which valid data was collected. Its value is 96 unless the CSU was brought online within the last 24 hours.
ds1ZeroCoding enumerates five zero-code suppression methods: ds1JammedBit (forces pulse in bit 8, yielding 1.344 Mbps data), ds1B8ZS, ds1InvertedHDLC, ds1HDB3, and ds1ZBTSI. The choice affects available data bandwidth and error susceptibility.
The RFC explicitly states that security issues are not discussed in this memo, providing no access control, authentication, or integrity guidance for SNMP management of DS1 interfaces.
The Unavailable Signal State is entered at the onset of 10 consecutive Severely Errored Seconds and cleared at the onset of 10 consecutive non-SES seconds. Seconds counted as Unavailable Seconds may not also be counted as Errored or Severely Errored Seconds; the initial 10 transition seconds are included in UAS counts but the 10 exit seconds are not.