As part of a communication session, a wireless source device can transmit audio and video data to a wireless sink device, and the wireless sink device can transmit user inputs received at the wireless sink device back to the wireless source device. In this manner, a user of the wireless sink device can control the wireless source device and control the content that is being transmitted from the wireless source device to the wireless sink device. As part of transmitting user input to the source device, the sink device can generate a data packet with a data packet header that includes a timestamp flag indicating the presence of a timestamp field, and the source device can process the data packet based on a timestamp in the timestamp field.