A computer system splits data to be transmitted into a plurality of reliable connections which are multiplexed through a smaller number of unacknowledged connections, such as connections that do not require acknowledgment and which may be VPN tunnels. A receiver then demultiplexes data received to obtain data flows over the reliable connections and transmits separate acknowledgements for each reliable connection. The computer system demultiplexes the acknowledgments and provides them to the corresponding reliable connections, which then retransmit any unacknowledged data. Delivery controllers executing on the computer system may be coupled to corresponding controllers executing on the receiver, with traffic between the delivery controllers (payload and acknowledgments) being multiplexed over one or more unacknowledged connections. In some embodiments, acknowledgments may be transmitted over a connection that is not multiplexed over the unacknowledged connections.