Independent clocks

In communication networks, independent clocks are free-running precision clocks located at the nodes which are used for synchronization.

Variable storage buffers, installed to accommodate variations in transmission delay between nodes, are made large enough to accommodate small time (phase) departures among the nodal clocks that control transmission. Traffic may occasionally be interrupted to allow the buffers to be emptied of some or all of their stored data.

Source: Federal Standard 1037C