Method for adjusting the data transmission rate for the transmission of payload data via a transmission path in a wide area network, according to which the data transmission rate for a path section of the transmission path that interconnects two endpoints (1, 2), formed by network elements, within an optical core network is adjusted between a minimum value and a maximum value in automated fashion in an iterative process, for the purpose of stipulating an operating point, in which a data transmission ensuring the reliable detection of a transmitter of one of the endpoints (1, 2) of transmitted payload signals by a receiver, which receives said payload signals, of the respective other endpoint (1, 2) is made possible at a high data transmission rate that is identical in both transmission directions, wherein the network elements that form the endpoints (1, 2), the interaction of which network elements is controlled by a network management system, are each equipped with a control unit and with FlexRate interfaces, namely with interfaces with a variably adjustable data transmission rate, having transmitting and receiving units, but the data rate to be adjusted for the path section is negotiated locally between the endpoints (1, 2) of the network management system in the iterative process without the involvement of said network management system, characterized in that a.) a first synchronous transmission operation involves both endpoints (1, 2) transmitting an identical test sequence at the same data transmission rate, and b.) subsequent synchronous transmission operations involve a respective endpoint (1, 2) transmitting a signal sequence that differs, according to a rule from the set of rules, from the respective previously transmitted signal sequence in terms of its data transmission rate and/or its type and that is either a test sequence again or a concluding sequence and that is determined according to the aforementioned rule on the basis of a comparison of the signals that are transmitted by the same respective endpoint (1, 2) during the preceding transmission operation with the signals received by said endpoint and a check, taking place at that time, to determine whether the signal sequence transmitted by the respective endpoint (1, 2) is reconstructable from the signal sequence received by the same endpoint (1, 2), and c.) an endpoint (1, 2) that has transmitted a signal sequence that is altered in comparison with the signal sequence of the preceding transmission operation both in terms of data transmission rate and in terms of type, namely the concluding sequence, repeatedly transmits this signal sequence without alteration in subsequent transmission operations until said endpoint receives the identical signal sequence, in terms of both its data transmission rate and its type, from the other endpoint (1, 2), and d.) the data transmission rate of the signal sequence according to step c.), which terminates the iteration, is the data transmission rate at which payload data are subsequently transmitted via the transmission path in the path section within the core network. a.) a first synchronous transmission operation involves both endpoints (1, 2) transmitting an identical test sequence at the same data transmission rate, and b.) subsequent synchronous transmission operations involve a respective endpoint (1, 2) transmitting a signal sequence that differs, according to a rule from the set of rules, from the respective previously transmitted signal sequence in terms of its data transmission rate and/or its type and that is either a test sequence again or a concluding sequence and that is determined according to the aforementioned rule on the basis of a comparison of the signals that are transmitted by the same respective endpoint (1, 2) during the preceding transmission operation with the signals received by said endpoint and a check, taking place at that time, to determine whether the signal sequence transmitted by the respective endpoint (1, 2) is reconstructable from the signal sequence received by the same endpoint (1, 2), and c.) an endpoint (1, 2) that has transmitted a signal sequence that is altered in comparison with the signal sequence of the preceding transmission operation both in terms of data transmission rate and in terms of type, namely the concluding sequence, repeatedly transmits this signal sequence without alteration in subsequent transmission operations until said endpoint receives the identical signal sequence, in terms of both its data transmission rate and its type, from the other endpoint (1, 2), and d.) the data transmission rate of the signal sequence according to step c.), which terminates the iteration, is the data transmission rate at which payload data are subsequently transmitted via the transmission path in the path section within the core network.