Definitions of Managed Object Extensions for Very High Speed Digital Subscriber Lines (VDSL) Using Single Carrier Modulation (SCM) Line Coding
Extracted elements (19)
The MIB is structured as an optional extension to RFC 3728 (VDSL-LINE-MIB) rather than incorporating SCM-specific objects into the base MIB. This design separates line-code-independent TC layer management (in RFC 3728) from line-code-specific PMD layer management, allowing implementations to support only the line coding they use.
This MIB is an optional extension to VDSL-LINE-MIB (RFC 3728). An SCM-based VDSL agent does not have to implement this MIB to be compliant with RFC 3728. The table relationship requires that when vdslLineCoding is set to SCM, vdslLineConfProfileName is used as the index to vdslLineSCMConfProfileBandTable.
All read-create objects defined in this MIB module SHOULD be stored persistently. This includes all band configuration profile objects and physical band performance objects, as well as interface indices and related VACM data.
Deployment of SNMP versions prior to SNMPv3 is NOT RECOMMENDED. It is RECOMMENDED to deploy SNMPv3 with cryptographic security enabled, including full support for SNMPv3 authentication and privacy mechanisms.
If the SCM VDSL Line Extension MIB is implemented, then all objects in the vdslSCMGroup MUST be implemented.
The objects in this extension MIB MUST NOT be used for VDSL lines using Multiple Carrier Modulation (MCM) line coding. If an object in this extension MIB is referenced by a line which does not use SCM, it has no effect on the operation of that line.
The VDSL-LINE-EXT-SCM-MIB defines the vdslSCMGroup containing two tables: vdslLineSCMConfProfileBandTable (transmit band configuration profiles) and vdslLineSCMPhysBandTable (current physical band parameters). This MIB is an optional extension to VDSL-LINE-MIB (RFC 3728) covering line code specific PMD layer objects for SCM VDSL lines.
The vdslLineSCMConfProfileBandConstellationSize object specifies the constellation size in log2 units with a range of 0..16, referencing T1E1.4/2000-011R3 Part 2 SCM specification.
The vdslLineSCMConfProfileBandRowStatus object controls row lifecycle: a profile is activated by setting it to 'active', at which point the system validates the profile. No columns may be modified while 'active'. The profile must be unreferenced from all associated lines before it can be deleted or set to 'notInService'.
The vdslLineSCMConfProfileBandTable contains transmit band descriptor configuration for VDSL SCM lines. For each profile associated with an SCM VDSL line, five entries exist (one per band), indexed by vdslLineConfProfileName and vdslLineSCMConfProfileBandId.
The vdslLineSCMPhysBandCurrAtn object reports the measured difference in total power transmitted by the peer Vtu and total power received by this Vtu on a given band, in units of 0.25 dB, ranging from 0 to 255.
The vdslLineSCMPhysBandCurrSnrMgn object reports noise margin as seen by each Vtu and band with respect to its received signal, in units of 0.25 dB, as a signed Integer32.
The vdslLineSCMPhysBandTable provides read-only current physical parameters for each SCM Vtu band. For each ifIndex associated with an SCM VDSL line, five entries exist (one per band), indexed by ifIndex and vdslLineSCMPhysBandId.
The VdslSCMBandId textual convention identifies SCM bands as an INTEGER with seven values: optionalBand (1) for the optional 25kHz-138kHz range, firstDownstreamBand (2), firstUpstreamBand (3), secondDownstreamBand (4), secondUpstreamBand (5), thirdDownstreamBand (6), and thirdUpstreamBand (7).
VdslLineSCMConfProfileBandEntry contains: BandId (VdslSCMBandId), InUse (TruthValue), CenterFrequency (Unsigned32, Hz), SymbolRate (Unsigned32, baud), ConstellationSize (Unsigned32 0..16, log2), TransmitPSDLevel (Unsigned32, -0.25 dBm/Hz), and RowStatus.
VdslLineSCMPhysBandEntry contains read-only current physical measurements: BandId, InUse (TruthValue), CurrCenterFrequency (Unsigned32, Hz), CurrSymbolRate (Unsigned32, baud), CurrConstellationSize (Unsigned32 0..16, log2), CurrPSDLevel (Unsigned32, -0.25 dBm/Hz), CurrSnrMgn (Integer32, 0.25 dB), and CurrAtn (Unsigned32 0..255, 0.25 dB).
IANA assigned the transmission value 228 to VDSL-LINE-EXT-SCM-MIB, placing the MIB module under the MIB-2 transmission subtree at OID { transmission 228 }.
Read access to physical band parameters (vdslLineSCMPhysBandTable objects) may provide knowledge enabling malicious behavior, such as applying intentional interference on physical bands. GET and NOTIFY access to these objects should be controlled, and values should possibly be encrypted when sent over the network via SNMP.
Read-create objects in vdslLineSCMConfProfileBandTable (InUse, TransmitPSDLevel, SymbolRate, ConstellationSize, CenterFrequency, RowStatus) are sensitive: SET operations without proper protection can negatively affect network operations. An end-user with write access could increase service levels or affect other users. Subscriber-initiated fluctuations could also generate sufficient SNMP notifications to overwhelm management interfaces.