Description: Number of basic rate interfaces on the IAD for which capacity is
reserved on the DSL link. The capacity is reserved in units of
timeslots, and the table below shows the number of timeslots reserved
as a function of dslLinkNumberOfBRA.

                       voice       dslLinkDynamicSlotAllocation
dslLinkNumberOfBRA   reservation       true(1)     false(2)
---------------------------------------------------------------
        0                0               0           0
        1                3              1-3          3
        2                5              1-5          5
        3                7              1-7          7
        4                9              1-9          9

If dslLinkNumberOfBRA is 0, no timeslots are reserved in the DSL link.
If dslLinkNumberOfBRA is non-zero, one timeslot is always reserved
and used for D-channel signalling. For each BRA allowed, exactly
two timeslots are reserved (one each for the two B-channels of the
basic rate interface). When dynamic (time)slot allocation is off,
reserved timeslots are unavailable for data. If dynamic slot
allocation is in effect, reserved voice timeslots are used only on
demand, that is when a phone call is being made. Reserved but unused
voice timeslots are then used for data, increasing the data rate.
The timeslot for the D-channel is not dynamically allocated. If a
D-channel is reserved, it is unavailable for data.
The value of this object cannot be set outside of the range 0..4. It
should be chosen such that the following conditions hold:
    dslLinkNumberOrBRA <= (dslLinkLineRate - dslLinkDataRate - 1) / 2
    dslLinkNumberOrBRA <= number of basic rate interfaces on the IAD
where the division should round towards zero. If the value violates
either of these conditions, the DSL link raises a 'configuration'
alarm.

Note that if the IAD is not connected, the link may raise the alarm
only when the IAD connects. It is allowed to set a value less than the
actual number of basic rate interfaces present on the IAD.