Definitions of Managed Objects for Asymmetric Digital Subscriber Line 2 (ADSL2)
Extracted elements (32)
A new ifType value (adsl2plus=238) was required rather than reusing adsl(94) because this MIB's management model is incompatible with RFC 2662: both documents coexist, and the ifType determines which MIB a management system must use, preventing management conflicts on deployments that support both ADSL and ADSL2/ADSL2+.
The profile-and-template abstraction was introduced because managed nodes may handle hundreds or thousands of XTU lines; provisioning every parameter individually would be burdensome, and most lines share identical configurations — templates (one line profile + up to four channel profiles) allow a single configuration to be shared across many lines.
This document does not obsolete RFC 2662 (ADSL MIB); both MIBs coexist, with ifType=adsl(94) requiring RFC 2662 management and ifType=adsl2plus(238) requiring this MIB. Deployers must ensure the correct MIB is used based on the assigned ifType.
A line configuration profile MUST include one or more mode-specific extensions, because a subset of line configuration parameters depends on the specific ADSL Mode (ADSL, ADSL2, or ADSL2+) and allowed annexes.
ADSL lines identified with ifType=adsl(94) MUST be managed with the MIB specified by RFC 2662. ADSL, ADSL2, and ADSL2+ lines identified with ifType=adsl2plus(238) MUST be managed with the MIB specified by this document.
All read-create objects and most read-write objects defined in this MIB module SHOULD be stored persistently; an exhaustive list of such objects is provided in Section 2.5.
Before a template can be deleted or taken out of service, it MUST first be unreferenced from all associated lines. Before a profile can be deleted, it MUST first be unreferenced from all associated templates.
For interfaces in systems implementing this MIB module, ifTable entries indexed by ifIndex MUST be persistent.
If an implementation allows modifying a profile or template while it is associated with a line, such changes MUST take effect immediately and MAY result in a restart of the units on that line.
If data for an interval is suspect or known to be invalid, the agent MUST report the interval as invalid, and MUST NOT generate notifications based upon the value of an invalid current 15-minute event bucket.
Implementations MUST provide a default profile named 'DEFVAL' for each profile and template type; this name is reserved and cannot be used for user-defined profiles.
Non-threshold notifications SHOULD be rate-limited (throttled) with an implementation-specific gap between consecutive notifications of the same event; rate-limited notifications are dropped and not queued.
Only one threshold crossing notification SHOULD be sent per 15-minute interval per interface; since counters reset every 15 minutes, notifications may recur no more than once per interval.
Systems implementing this MIB module SHOULD practically support at least 16 15-minute history interval buckets (as specified in ITU-T G.997.1 §7.2.7.2) and SHOULD support at least 1 previous 1-day bucket.
The ability to generate coldStart/warmStart (per RFC 3418) and linkUp/linkDown (per RFC 2863) SNMP notifications is REQUIRED.
The ifFixedLengthGroup from RFC 2863 MUST be supported; the ifRcvAddressGroup does not apply to this MIB module.
The ifPhysAddress object MUST have an octet string with zero length for ADSL2 interfaces.
The SNMP agent MUST automatically create rows in adsl2ChannelStatusTable and adsl2PMChCurrTable when the number of bearer channels increases, and MUST destroy rows in those tables plus adsl2PMChHist15MinTable and adsl2PMChHist1DTable when the count decreases.
An ADSL/ADSL2/ADSL2+ line consists of two units — ATU-C (central office) and ATU-R (remote/subscriber) — carrying up to four independent bearer channels over a single twisted-pair span.
The Adsl2InitResult textual convention defines six result codes for a full initialization attempt: noFail(0), configError(1), configNotFeasible(2), commFail(3), noPeerAtu(4), and otherCause(5), as defined in ITU-T G.997.1 §7.5.1.3.
The Adsl2LineStatus BITS textual convention reports endpoint failure state: noDefect(0), lossOfFrame(1), lossOfSignal(2), lossOfPower(3), and initFailure(4); lossOfPower is typically ATU-R only and initFailure is never active on ATU-R.
The Adsl2PowerMngState textual convention defines four power management states: L0 (full power), L1 (low power for G.992.2), L2 (low power for G.992.3/4/5), and L3 (idle). Autonomous transitions are controlled via the Adsl2LConfProfPmMode BITS field.
The Adsl2RaMode textual convention defines three rate-adaptation behaviors: manual(1) — no adaptation, target a fixed rate; raInit(2) — adapt during initialization only; dynamicRa(3) — adapt during both initialization and SHOWTIME.
The MIB module is organized into distinct groups: Line Configuration/Status, Channel Status, Subcarrier Status, Unit Inventory, Current Performance, 15-Minute Interval Performance, 1-Day Interval Performance, Configuration Template and Profile, Alarm Configuration Template and Profile, and Notifications.
IANA assigned ifType=adsl2plus(238) for Asymmetric Digital Subscriber Loop Version 2 and all variants, and also assigned transmission number 238 to the ADSL2-LINE-MIB module (OID transmission.238).
The MIB contains numerous read-write and read-create objects (configuration profiles, templates, line commands) that can directly affect ADSL line operation; unauthorized access could disrupt service for all subscribers on managed lines. Implementors are directed to use SNMPv3 with authentication and privacy to protect these objects.
Adsl2LastTransmittedState enumerates initialization states for ATU-C (0=G9941 through 32=Showtime) and ATU-R (100=G9941 through 131=Showtime), recording the last successfully transmitted state during a full initialization sequence from G.994.1 handshake through Showtime.
Adsl2PsdMaskDs encodes the downstream PSD mask as an OCTET STRING (SIZE 0..96) of up to 32 breakpoints; each breakpoint occupies 3 octets: 2 octets for sub-carrier index and 1 octet for PSD reduction (0–255 in units of 0.5 dBm/Hz).
Adsl2PsdMaskUs encodes the upstream PSD mask as an OCTET STRING (SIZE 0..12) of up to 4 breakpoints; each breakpoint occupies 3 octets with the same sub-carrier index and PSD reduction encoding as the downstream mask.
Adsl2ScMaskDs is an OCTET STRING (SIZE 0..64) representing a 512-bit bitmap where each bit corresponds to one downstream sub-carrier bin; a value of 1 indicates the bin is not in use. Adsl2ScMaskUs is an OCTET STRING (SIZE 0..8) for 64 upstream bins.
Adsl2TransmissionModeType is a 56-bit BITS construct (bits 0–55) enumerating each supported ADSL/ADSL2/ADSL2+ transmission mode; bits 13–17, 22–23, 26–27, 44–45, and 52–55 are reserved.
Adsl2Tssi encodes transmit spectrum shaping as an OCTET STRING (SIZE 0..96) of up to 32 breakpoints; each breakpoint is 3 octets (2-octet sub-carrier index + 1-octet shaping value 0–127 in units of -0.5 dB; value 127 means the sub-carrier is not transmitted).