A method of managing communication between a host device and a USB device via a non-USB extension medium is provided. A downstream facing port device (DFP device) receives a data request packet that includes a first buffer count from an upstream facing port device (UFP device) via the non-USB extension medium. The DFP device determines a number of data packets to request from the USB device based on a free buffer count tracked by the DFP device that represents an amount of buffer space available on the UFP device. The DFP device generates a synthetic data request packet that includes a second buffer count based on the determined number of data packets to request from the USB device. The DFP device receives a set of data packets from the USB device responsive to the synthetic data request packet, and transmits the set of data packets to the UFP device.