For quantum key distribution networks (QKDN), Recommendation ITU-T Y.QKDN-iwfr specifies framework of QKDN interworking (QKDNi). This Recommendation describes the overview of interworking QKDNs, the reference models, and the functional models of gateway functions (GWFs) and interworking functions (IWFs). The configurations for QKDNi are specified. Appendix I includes QKDNi with different key relay schemes.