A master Timestamp Synchronization Circuit (TSC) in a Cable Modem Termination System (CMTS) estimates a master timestamp value for an upcoming time reference. The master TSC sends the master timestamp value asynchronously over an Internet Protocol (IP) network to slave TSCs in other CMTSs. The slave TSC compares a local timestamp value with the master timestamp value when the upcoming time reference occurs. If the local timestamp value does not match the master timestamp value, the slave TSC is resynchronized using the master timestamp value.