Using ALTO Protocol to Address SD-QKD Federation in Multi-Domain Scenarios

Quantum Key Distribution (QKD) technologies are rapidly evolving from a set of isolated mono vendor links, towards real networks with relay schemes able to flexibly interconnect applications accessing their key serving nodes. To that end, Software-Defined Networking (SDN) technologies are being proposed as the paradigm to provide SD-QKD nodes with the necessary network topology information to establish QKD services based on Service-Level Agreements (SLAs) and will be essential in many of the national EuroQCI deployments. However, existing SDN solutions in multi-domain scenarios with little information of other domains, such as the ones foreseen in the future multi-national Euro-QCI. This paper proposes leveraging the Application-Layer Traffic Optimization (ALTO) protocol to enhance network visibility and streamline interconnection procedures, the main goal is to do a theoretical approach to the solution, defining how the implementation of the solution should be if we follow the current standardization of used technologies. ALTO facilitates identifying optimal QKD paths and adhering to service agreements across diverse domains, offering a novel solution to SDN deployment challenges. Its integration promises improved network management and unprecedented interoperability in QKD networks, advancing SDN and multi-layer networking.