Preventing or repairing any arising problem. It is centred on the maintenance performance done by an operator. Use Cases: - **Hardware extension/replacement**, providing service and granting its quality while the hardware is replaced. - **Software upgrade**, installation of new software updates. - **Network monitoring**, which consists of performing measurements and analysis to the network in order to recognise insufficiencies or needed improvements. - **Failure recovery**, the network has to be able of recovering after a breakdown.