This read-only Gauge reports the number of Controlled Slip Seconds encountered by this DS1 interface over the previous 24-hour interval, counting seconds where the receiving buffer had to repeat or delete a frame due to a clock synchronization mismatch between the transmit and receive timing sources. Since slips are specifically a timing/clocking problem rather than a signal-quality problem, a rising dsx1TotalCSSs is a strong indicator to check dsx1TransmitClockSource configuration for a timing-hierarchy mismatch rather than looking at line coding or physical cabling. An engineer seeing daily dsx1TotalCSSs consistently nonzero on an otherwise clean DS1 would suspect this interface and its peer are both configured for localTiming, creating a clock conflict, rather than one properly deriving timing from the other.