Hello,

It is given by the technical construction of serial interfaces. Out of two devices connected by serial link, one of them is responsible for providing the clocking signal and both devices adapt to that clocking. This clocking responsibility is given to the DCE device, as that is the devices that is also connected to the local loop owned by the WAN provider. It is aware of its bandwidth limitations, therefore it also limits the speed on the serial link by the clocking so that the DTE devices does not overload the physical data-carrying capacity of the local loop.

So, the clocking function is reasonable only on the DCE device.

Best regards,

Peter