"The Virtual Private Wire Service (VPWS)@ detailed in RFC 4664@ provides point-to-point connections between pairs of Customer Edge (CE) devices. It does so by binding two Attachment Circuits (each connecting a CE device with a Provider Edge (PE) device) to a pseudowire (connecting the two PEs). In general@ the Attachment Circuits must be of the same technology (e.g.@ both Ethernet or both ATM)@ and the pseudowire must carry the frames of that technology. However@ if it is known that the frames' payload consists solely of IP datagrams@ it is possible to provide a point-to-point connection in which the pseudowire connects Attachment Circuits of different technologies. This requires the PEs to perform a function known as ""Address Resolution Protocol (ARP) Mediation"". ARP Mediation refers to the process of resolving Layer 2 addresses when different resolution protocols are used on either Attachment Circuit. The methods described in this document are applicable even when the CEs run a routing protocol between them@ as long as the routing protocol runs over IP."