A method of operating a network management node in a cellular telecommunications network, the cellular telecommunications network having a first central base station unit connected to a first distributed base station unit (20, 80), the first central base station unit configured to communicate with the first distributed base station unit (20, 80) using either a first functional split in which a first set of protocol functions are implemented by the first central base station unit and a second set of protocol functions are implemented by the first distributed base station unit (20, 80) or a second functional split in which a third set of protocol functions are implemented by the first central base station unit and a fourth set of protocol functions are implemented by the first distributed base station unit (20, 80), wherein the network management node includes a database of reference processing resource utilisation values each being a value of processing resource utilisation for either the first central base station unit or first distributed base station unit (20, 80) when using either the first functional split or the second functional split, the method comprising the steps: receiving a processing capability value of the first central base station unit and a processing capability value of the first distributed base station unit (20, 80), wherein the first central base station unit initially communicates with the first distributed base station unit (20, 80) using the first functional split; determining that the reference processing resource utilisation value of at least one of the first central base station unit and the first distributed base station unit (20, 80), when using the first functional split, exceeds the received respective processing capability value of the first central base station unit and/or the first distributed base station unit (20, 80); identifying the second functional split by determining that a processing resource utilisation value of the first central base station unit when using the second functional split, based on the reference processing resource utilisation value of the first central base station unit when using the second functional split as stored in the database of reference processing resource utilisation values, is less than the received processing capability value of the first central base station unit and by determining that a processing resource utilisation value of the first distributed base station unit (20, 80) when using the second functional split, based on the reference processing resource utilisation value of the first distributed base station unit (20, 80) when using the second functional split as stored in the database of reference processing resource utilisation values, is less than the received processing capability value of the first distributed base station unit (20, 80); and causing the first central base station unit and first distributed base station unit (20, 80) to communicate using the second functional split. receiving a processing capability value of the first central base station unit and a processing capability value of the first distributed base station unit (20, 80), wherein the first central base station unit initially communicates with the first distributed base station unit (20, 80) using the first functional split; determining that the reference processing resource utilisation value of at least one of the first central base station unit and the first distributed base station unit (20, 80), when using the first functional split, exceeds the received respective processing capability value of the first central base station unit and/or the first distributed base station unit (20, 80); identifying the second functional split by determining that a processing resource utilisation value of the first central base station unit when using the second functional split, based on the reference processing resource utilisation value of the first central base station unit when using the second functional split as stored in the database of reference processing resource utilisation values, is less than the received processing capability value of the first central base station unit and by determining that a processing resource utilisation value of the first distributed base station unit (20, 80) when using the second functional split, based on the reference processing resource utilisation value of the first distributed base station unit (20, 80) when using the second functional split as stored in the database of reference processing resource utilisation values, is less than the received processing capability value of the first distributed base station unit (20, 80); and causing the first central base station unit and first distributed base station unit (20, 80) to communicate using the second functional split.