the invention relates to a method to discover optical network units with different speed capabilities in an ethernet passive optical network by an optical line termination , where logical links in the network are identified by logical link ids , and the olt can transmit and receive data with 1 gbit / s - speed and 10 gbit / s - speed , and the discovery process is handled in the olt by a multi point control process , which exchanges messages as data units with the onus . this is achieved by extending the standard mpcpdus in a way , that backward compatability is assured .