In general, the subject matter described in this specification can be embodied in methods, systems, and program products for generating a schedule to transmit data on a network. The method includes accessing information that identifies a quantity of data that a particular client device has designated for transmission. The method includes determining, using the information that identifies the quantity of data for each of multiple client devices, a first schedule that identifies a subset of packet time segments, from a frame that includes packet time segments, during which a first client device is permitted to transmit data to the computing system. The first client device is one of the multiple client devices. The information includes transmitting the first schedule. The schedule includes receiving a transmission of data from the first client device during the identified subset of packet time segments in accordance with the schedule.