This MIB module serves as an enterprise-specific extension of
the ADSL-LINE-MIB.  The structure of this MIB module shadows
the structure of the ADSL-LINE-MIB, table for table.  The tables
defined by this MIB module contain managed objects that meet the
following criteria:

1)  A managed object represents an attribute or characteristic
    specific to DMT (Digital Multi-Tone) modems.

2)  The ADSL-DMT-LINE-MIB does not already contain a managed
    object representing the same information as a managed
    object.

Observe that entries contained by the tables in this MIB module
do not augment the corresponding entries in the ADSL-LINE-MIB,
as every modem represented by the ADSL-LINE-MIB is not
necessarily a DMT modem.

Also observe that entries contained by the tables in this MIB
module do not augment the corresponding entries in the
ADSL-DMT-LINE-MIB, as this assumes that the ADSL-DMT-LINE-MIB
defines tables that correspond to every table defined by the
ADSL-LINE-MIB.  At this time, this assumption does not hold
true.

*** DEFINITIONS ***

AGGREGATE DATA RATE
    Data rate transmitted by an ADSL system in any one
    direction.  This includes both net data rates and overhead
    used by the system, including:
        - EOC
        - AOC (ADSL Overhead Control channel)
        - CRC (Cyclic Redundancy Check) check bytes
        - fixed indicator bits for OAM (Operatings,
          Administration, and Maintenance)
        - synchronization control bytes
        - capacity for bearer channel synchronization control

BEARER CHANNEL
    A user data stream of a specific data rate that is
    transported transparently by an ADSL system over one of the
    simplex channels (i.e., AS0, AS1, AS2, or AS3) or one of the
    duplex channels (i.e., LS0, LS1, or LS2).

BIN
    DMT line coding divides the frequency spectrum above the
    voice band of a line (i.e., 0-4 kHz) into 255 sub-carriers,
    each supporting 4.3125 kHz of bandwidth.  A 'bin' refers to
    a single sub-carrier.

DATA SYMBOL RATE
    The average symbol rate (after allowing for the overhead of
    the sync symbol) at which symbols carrying data are
    transmitted; that is, 4000 symbols/second.

DOWNSTREAM
    The flow of data in the direction from the ATU-C to ATU-R.

LINE RATE
    The total data rate supported by a line; that is,
    (sum of b(i) for all i) * 4 kbps.

MARGIN (also referred to as 'SNR margin')
    The difference between the SNR of the received signal and
    the SNR required to provide a BER of 10E-7.

NET DATA RATE
    The data rate that is available for user data in any one
    direction; for the downstream direction this is the sum of
    the simplex and duplex bearer channel rates.

SPLITTER
    Filters that separate the high frequency signals (ADSL)
    from the voice band signals; (frequently called POTS
    splitters even though the voice band signals may comprise
    more than just POTS).

SYMBOL
    The number of bits the transmitter is capable of
    multiplexing and modulating over all the bins in a single
    signalling interval.

SYMBOL RATE
    The rate at which all symbols, including the sync
    symbol, are transmitted; that is, (69/68) * 4000
    symbols/sec; contrasted with the data symbol rate.

TOTAL DATA RATE
    The aggregate data rate (q.v.) plus Reed-Solomon FEC
    overhead.

UPSTREAM
    The flow of data in the direction from the ATU-R to ATU-C.

*** ABBREVIATIONS, ACRONYMS, AND SYMBOLS ***

ADSL - Asymmetric Digital Subscriber Line.

ATM - Asynchronous Transfer Mode.

ATU-C - ADSL Transceiver Unit, Central Office end.

ATU-R - ADSL Transceiver Unit, Remote terminal end.

b(i) - the number of bits (i.e., constellation size) modulated
    on bin i.

BER - Bit Error Ratio.

DMT - Discrete MultiTone.

DSL - Digital Subscriber Line.

EOC - Embedded Operations Channel.

FEC - Forward Error Correction.

SNR - Signal-to-Noise Ratio.

STM - Synchronous Transfer Mode.