The QKDN is able to cover a wide area by interworking multiple QKDNs, which is called to QKDN interworking (QKDNi). One of the challenges of the QKDNi is to assure the network interworking performance and that different quality of service (QoS)/quality of experience (QoE) requirements of different interworking application scenarios are met. The requirements of QoS assurance for QKDNi specified in [ITU-T Y.3817] address these challenges. Based on the requirements, this Recommendation specifies the functional architecture, associated functional entities and reference points and a basic operational procedure.