A network adapter includes a host interface and a scheduler. The host interface is configured to receive, from one or more hosts, packets for transmission to respective destinations over a network. The scheduler is configured to synchronize to a time-division schedule that is employed in the network, the time-division schedule specifying (i) multiple time-slots and (ii) multiple respective groups of the destinations that are reachable during the time-slots, and, based on the time-division schedule, to schedule transmission times of the packets to the network on time-slots during which the respective destinations of the packets are reachable.