A source node for addressing target nodes (44, 46) in a communication system (10), the source node configured to be part of an Ethernet domain (20) and the target nodes (44, 46) configured to be part of a Multiple Protocol Label Switching (MPLS) domain (40) that is connected to the Ethernet domain (20) via an interworking node (30). The source node is further configured to: i) generate a message (51) comprising an identifier of the source node, an identifier of the interworking node (30), and an identifier of a certain target node (44) of the target nodes (44, 46), ii) send the message (51) to the certain target node (44) via the interworking node (30), and iii) receive from the certain target node (44) via interworking node (30) a reply (54) to the message (51). An alternate source node, related interworking nodes and methods are also described.