Techniques for synchronizing the clock of a local telecommunications
network connected to a remote clock source through an asynchronous
transport network such as an Ethernet metropolitan area transport
network. A basic holdover loop for retaining the current reconstructed
clock frequency signal receives weighted corrections from an open loop
and a network time protocol filter loop. The open loop measures data
packet interarrival times on the local network and calculates a first
reconstructed clock frequency signal. The network time protocol loop
applies network time protocol to generate timestamps over the
asynchronous transport network which are used to generate a second
reconstructed clock frequency signal. The first and second reconstructed
clock frequency signals are combined using dynamically adjusted weight
factors and compared with the current reconstructed clock frequency
signal to correct the latter which then synchronizes the clock of the
local telecommunications network.