This object is used to index this table.
At the head end:
When a threshold is created on a per subscriber unit basis,
this object should reflect the MAC address of the subscriber
unit.
When a threshold is created on a per channel basis, this
object must be set to zero(00 00 00 00 00 00).
At the subscriber end:
When creating a threshold , this object must always be set
to zero (00 00 00 00 00 00).