This attribute indicates the total number of seconds that the interface has been in an unavailable state. An unavailable state occurs at the onset of 10 consecutive Severely Errored Seconds. When the unavailable state is entered, the 10 Severely Errored Seconds are immediately transfered to the count of unavailableSeconds by incrementing the count of unavailSec by 10 and decrementing the count of sevErroredSec by 10. Whilst in the unavailable state, an unavailableSecond is counted for each SES or SEFS that occurs, and the count of SES and SEFS are both inhibited. The unavailable state is cleared at the onset of 10 consecutive seconds which are not Severely Errored Seconds.