The MIB module defining objects for the management of a pair
of VDSL transceivers at each end of the VDSL line.  Each such
line has an entry in an ifTable which may include multiple
transceiver lines.  An agent may reside at either end of the
VDSL line.  However, the MIB is designed to require no
management communication between them beyond that inherent in
the low-level VDSL line protocol.  The agent may monitor and
control this protocol for its needs.

VDSL lines may support optional Fast or Interleaved channels.
If these are supported, additional entries corresponding to the
supported channels must be created in the ifTable.  Thus a VDSL
line that supports both channels will have three entries in the
ifTable, one for each physical, fast, and interleaved, whose
ifType values are equal to vdsl(97), fast(125), and
interleaved(124), respectively.  The ifStackTable is used to
represent the relationship between the entries.

Naming Conventions:
    Vtuc -- (VTUC) transceiver at near (Central) end of line
    Vtur -- (VTUR) transceiver at Remote end of line
    Vtu  -- One of either Vtuc or Vtur
    Curr -- Current
    Prev -- Previous
    Atn  -- Attenuation
    ES   -- Errored Second.
    SES  -- Severely Errored Second
    UAS  -- Unavailable Second
    LCS  -- Line Code Specific
    Lof  -- Loss of Frame
    Lol  -- Loss of Link
    Los  -- Loss of Signal
    Lpr  -- Loss of Power
    xxxs -- Sum of Seconds in which xxx has occured
            (e.g., xxx = Lof, Los, Lpr, Lol)
    Max  -- Maximum
    Mgn  -- Margin
    Min  -- Minimum
    Psd  -- Power Spectral Density
    Snr  -- Signal to Noise Ratio
    Tx   -- Transmit
    Blks -- Blocks

Copyright (C) The Internet Society (2004).  This version
of this MIB module is part of RFC 3728: see the RFC
itself for full legal notices.