# The Rise of Quantum Information and Communication Technologies
## 3 Management and Control of QKD Networks
If KMs do not have direct KM links between them, they should share the necessary number of keys via key relay. KMs then ask the QKDN controller(s) about an appropriate relay route. Consequently, the keys are transferred and finally supplied to the cryptographic applications. Once the keys have been supplied to the cryptographic applications, the KMs should apply the key management policy, such as by deleting or preserving the keys. * A QKDN control layer--The QKDN control functions must control QKDN resources to ensure secure and stable operations of a QKDN. QKDN control functions are provided by QKDN Controller(s) and, mainly, include the following:
* The control of key relay routes including rerouting (e.g., when a failure or eavesdropping occurs) between the two end points of the cryptographic application, which require the key;
* The control of KMs and KM links;
* The control of QKD modules and QKD links;
* Authentication and authorization control;
* Quality of service (QoS) and charging policy control. * A QKDN management layer--A QKDN manager located in this layer monitors and manages the QKDN as a whole. The QKDN manager gathers information about the performance of QKD modules and QKD links (including quantum relay points) in the quantum layer and key management information in the key management layer, to monitor these two layers. Moreover, the QKDN manager interacts with the QKDN controller to support the management and control functions of the QKDN. The basic functions are as follows:
* Fault, accounting, configuration, performance and security (FCAPS) management;
* The status of whole-QKDN monitoring;
* Support of key life cycle management in KM;
* Authentication and authorization management;
* QoS and charging management. As previously mentioned, control and management functionalities are essential for the industrialization of QKDN solutions ready for deployment and integration with traditional telecommunication networks. Therefore, EQUO innovation activities focused on these functionalities and identified the relationships between them (the QKDN control layer and QKDN management layer) and the other functional layers. A feasibility study on the applicability of ITU-T Rec. Y.3804 \"Quantum key distribution networks--Control and management\" has been pursued as well. This recommendation specifies control and management functions and procedures for QKDNs, covering the following:  
* Functional elements of QKDN control, management, and orchestration;
* Functions of QKDN control, management, and orchestration;
* Procedures of QKDN control, management, and orchestration. Figure 2 highlights functional components and reference points relevant to QKDN control and management in a QKDN. The following control functions are supported:  
* Routing control--this provisions an appropriate key relay route between two end points of KMs in the key management layer. * Configuration control--this is responsible for the acquisition of control related configuration information on QKD modules and QKD links in the quantum layer and on KMs and KM Links in the key management layer. Moreover, it controls the state of these components and can reconfigure QKD links and KM links if an alarm or failure diagnosis is noted. * Access control--this provides capabilities to verify the claimed identity of functional components under the control and support of the QKDN controller and to restrict the functional components to pre-authorized activities or roles;
* Session control--the session control function supports the communication between KMs to establish the end-to-end key relay route or to supply keys to cryptographic  
Figure 2: Functional elements and reference points relevant to QKDN control and management (source: ITU-T Y.3804). *: Traditional fault, configuration, accounting, performance, and security (FCAPS) functionality which is not specific to QKDN is outside the scope of this Recommendation. applications in the service layer of the user network. The session control function initiates, maintains, and terminates the session.