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Adaptive Clocking for SAToP Bundles Overview


The goal of adaptive clocking is to prevent buffer anomalies by adjusting the clocks so that they are the same at each end of the network. If the clocks are not the same at each end of the network, the data rate entering and exiting buffers will not be the same, which causes a buffer underflow or overflow.

Adaptive clocking works by gathering information on packets arriving from the IP network and using that information to determine if adjustments need to be made to the local clock to maintain frequency lock with the remote end. This process is called adaptive time domain processing (ATDP). ATDP provides rapid convergence to the correct clock, and does not vary due to changes in the average jitter buffer fill. As a result, a circuit continuously operates without a buffer re-center, even when clock references are not used.

SAToP bundles support adaptive clocking with the external transmit (TX) clock. With this type of clocking:

  • Data received from the local user equipment that is bound to the IP network is clocked using the CTP external user clock (the transmit timing clock).

  • Data received from the remote CTP device and bound for the interface is adaptively clocked with the recovered clock from the user equipment that is connected to the remote CTP device.

This configuration allows for independent adaptive configuration in each direction. With this method, the user equipment can send packets into the network with their local clock, and the remote end CTP devices adaptively recover this clock. This clocking method is useful when the port speed is high or the cable length between the user equipment and CTP device is large.