Number of times interface saw the carrier
signal transition.
For example, if a T1 line is unplugged,
then framer will detect the loss of signal
(LOS) on the line and will count it as a
transition.
Discontinuities in the value of this variable
can occur at re-initialization of the
management system, and at other times as
indicated by the values of
cieIfInterfaceDiscontinuityTime.