A controller of a network, including routers to forward flows of packets originated at senders to receivers along distinct network paths each including multiple links, such that the flows merge at a common link that imposes a traffic bottleneck on the flows, receives from one or more of the routers router reports that each indicate an aggregate packet loss that represents an aggregate of packet losses experienced by each of the flows at the common link. The controller sends to the senders aggregate loss reports each including the aggregate packet loss so that the senders have common packet loss information for the common link on which to base decisions as to whether to switch from delay-based to loss-based congestion control modes when implementing dual-mode congestion control of the flows. In lieu of the controller, another example employs in-band router messages populated with packet losses by the routers the messages traverse.