An input/output (I/O) device includes a host interface for connection to a host device having a memory and a network interface, which is configured to receive, over a network, data packets associated with I/O operations directed to specified virtual addresses in the memory. Packet processing hardware is configured to translate the virtual addresses into physical addresses and to perform the I/O operations using the physical addresses, and upon an occurrence of a page fault in translating one of the virtual addresses, to transmit a response packet over the network to a source of the data packets so as to cause the source to refrain from transmitting further data packets while the page fault is serviced.