Abstract: A network interface device (15a) has a mass storage device interface (3a), which emulates a hard disk controller to transfer network traffic between a node (Ia) and the network. As a result, the node (Ia), typically a computer, is presented with a virtual hard disk (4a), which network traffic (e.g. data) can be written to and read from using standard hard disk protocols, e.g. SATA or PATA. In a computer cluster (13), several network interface devices (15a-15c) may be integrated in a router (8) having a switch (9). The router may connect to optional components such as hard disks (17a, 17b), a processor (18) and a Ethernet connection (19).