In one embodiment, a device receives data from a network at a TCP buffer at a selected data rate, and copies the data from the TCP buffer to a decoder buffer at a reading rate. Once decreasing the reading rate to decrease a level of the decoder buffer, the device may increase the reading rate to an upshift probe rate, and monitors a TCP buffer level during reading at the upshift probe rate to determine whether the network can support the upshift probe rate. If the TCP buffer level decreases to a lower threshold during the upshift probe rate, the device returns to read data from the TCP buffer by the decoder buffer at the reading rate. If the TCP buffer level stays above the lower threshold during the upshift probe rate, the device may trigger a corresponding upshift in a send rate from a sender of the data.