Building fault-tolerant hardware clocks from COTS components

Clocks with a bounded drift rate are an important tool in the construction of dependable applications. However, the drift rates of clocks provided by operating systems on some computing platforms are not always bounded, e.g. due to lost interrupts or leap seconds. We show how one can build clocks with a bounded drift rate from components off-the-shelf (COTS). Our approach can be used to achieve a tight synchronization with UTC (Coordinated Universal Time) in systems with access to at least one GPS (Global Positioning System) receiver