Apparatus for data communication includes a network interface for connection to a packet data network and a host interface for connection to a host computer, which includes a central processing unit (CPU) and a host memory. Packet processing circuitry receives, via the host interface, from a kernel running on the CPU, associations between multiple remote direct memory access (RDMA) sessions and multiple different User Datagram Protocol (UDP) 5-tuple, which are assigned respectively to the RDMA sessions, and receives from an application running on the CPU a request to send an RDMA message, using a selected group of one or more of the RDMA sessions, to a peer application over the packet data network, and in response to the request, transmits, via the network interface, one or more data packets using a UDP 5-tuple that is assigned to one of the RDMA sessions in the selected group.