Methods and systems for data flow control include establishing a first connection between a gateway and a network client responsive to a connection request from the network client; establishing a second connection between the gateway and a server specified by the connection request; determining a user class for the network client based on a level of network congestion detected at the gateway based on throughput and round-trip-time delays; modifying a data flow received at the gateway on the second connection to remove data from the flow based on the determined user class of the network client; and transmitting the modified data flow to the network client via the first connection.