This object specifies the flow identifier value received from
the CDL network that identifies this elementary packet stream
at this interface.
Note that if CDL is not enabled on this interface, this
represents the flow identifier value passed to this interface
from the cross connect fabric. If the cross connect fabric
does not map the flow identifier value for this elementary
packet stream, this is the value passed from the CDL
aggregation interface on the other side of the cross connect.