OAM data is automatically configured by each node of an Ethernet network. The OAM data is required to support an OAM signalling session associated with a connection for carrying data traffic between nodes. The OAM data can be derived from data already associated with all endpoints of the connection. The node can derive the OAM data autonomously. A node which is an endpoint of an OAM signalling session automatically derives an identifier for the first endpoint. The first identifier can be autonomously derived by the node and other signalling content, such as source MAC address, is used to differentiate OAM signalling messages. Alternatively, a node can automatically configure the first identifier on the basis of information stored locally at the node and signalling with a second endpoint. The OAM data can be IEEE 802.1ag or ITU Y.1731 data.