Described embodiments include a system that includes a network interface and a processor. The processor is configured to identify, via the network interface, a state of congestion in a communication channel between a base station belonging to a cellular network and a client device, to calculate, responsively to the state of congestion, a maximum sustainable encoding bit rate (MSEBR) for a video that is being downloaded by the client device, from a server, via the communication channel, the video being encoded at a plurality of different predefined bit rates, and to inhibit the client device, in response to calculating the MSEBR, from downloading a segment of the video that is encoded at any one of the predefined bit rates that exceeds the MSEBR. Other embodiments are also described.