A network adapter includes a port and one or more circuits. The port communicates packets over a network in which switches forward packets in accordance with tuples of the packets. The one or more circuits are to hold a user-programmable scheme specifying assignments of the packets of a given flow destined to a peer node to sub-flows having respective different tuples, assign first packets of the given flow to one or more of the sub-flows in accordance with the user-programmable scheme, by setting respective tuples of the first packets, transmit the first packets to the peer node via the port, monitor notifications received from the network, the notifications being indicative of respective states of the sub-flows, based on the notifications and on the user-programmable scheme determine an assignment of second packets of the given flow to the sub-flows, and transmit the second packets to the peer node via the port.