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arXiv:2608.17539 · International Conference on Quantum Communications, Networking, and Computing (QCNC)

Software Defined Networks Key Relay for Large-Scale Quantum Key Distribution Networks

Stephan Laschet, Gergely Lendvay, Thomas Lorünser, Paul TJ James, Luca Torresetti, Alessandro Colombo

Published Apr 6, 2026• 0 citations
arXivHTMLPDF

Abstract

This work addresses the orchestration of large-scale Quantum Key Distribution Networks (QKDNs) using Software Defined Networking (SDN). Building on ETSI and ITU specifications, common best practices and architectures are outlined. The main task of the SDN Controller is to aggregate technical key performance indicators (KPI) from the network and, based on these, select the optimal path. Multiple path selection algorithms, based on Dijkstra or a maximum-minimum capacity algorithm, with built-in load balancing are presented. The algorithms were tested in simulations and their performances, and tradeoffs, are discussed. Additional critical aspects related to SDN controlled QKDNs are discussed, such as query batching, multi-path selection and group key capabilities. An oblivious multi-party protocol is proposed for relay path selection in a multi-domain scenario, so providers don't have to disclose sensitive information about their QKDN. These contributions aim to enhance scalability, resilience and interoperability in quantum-secure network infrastructures.

DOI
10.1109/qcnc69040.2026.00115

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This work addresses the orchestration of large-scale Quantum Key Distribution Networks (QKDNs) using Software Defined Networking (SDN). Building on ETSI and ITU specifications, common best practices and architectures are outlined. The main task of the SDN Controller is to aggregate technical key performance indicators (KPI) from the network and, based on these, select the optimal path. Multiple path selection algorithms, based on Dijkstra or a maximum-minimum capacity algorithm, with built-in load balancing are presented. The algorithms were tested in simulations and their performances, and tradeoffs, are discussed. Additional critical aspects related to SDN controlled QKDNs are discussed, such as query batching, multi-path selection and group key capabilities. An oblivious multi-party protocol is proposed for relay path selection in a multi-domain scenario, so providers don't have to disclose sensitive information about their QKDN. These contributions aim to enhance scalability, resilience and interoperability in quantum-secure network infrastructures.
This paper demonstrates the use of software-defined networking (SDN) orchestration to integrate regionally separated networks in which different network parts use incompatible key management systems (KMSs) managed by different SDN controllers to ensure end-to-end QKD service provisioning to deliver the QKD keys between geographically different QKD networks. The study focuses on scenarios in which different parts of the network are managed separately by different SDN controllers, requiring an SDN orchestrator to coordinate and manage these controllers. In practical network deployments, operators often utilize multiple vendors for their network equipment. This practice also enables the expansion of the QKD network's coverage by interconnecting various QKD networks equipped with devices from different vendors. However, as coordinating different parts of the QKD network is a complex task, this paper proposes the implementation of an SDN orchestrator which acts as a central entity to manage multiple SDN controllers, ensuring end-to-end QKD service provisioning to address this challenge. For instance, when there are multiple border nodes to interconnect different networks, the SDN orchestrator calculates the path in advance for the end-to-end delivery of keys between initiating and target applications belonging to different networks. This path selection requires the SDN orchestrator to gather information from each SDN controller managing the respective parts of the QKD network. This work shows the practical implementation of SDN orchestration for interoperable KMS in commercial QKD networks in South Korea. By employing an SDN orchestrator, it becomes possible to coordinate multiple SDN controllers and ensure the efficient and secure delivery of QKD keys between different QKD networks with varying vendor equipment.
With the advent of powerful quantum computers, an emerging quantum-resilient security mechanism within existing networks is crucial. Thus, Quantum Key Distribution (QKD), which generates symmetric secret keys with Information-Theoretical Security (ITS) for secure point-to-point communication, is present as a solution. Despite QKD’s potential, its deployment is challenging due to significant investment and infrastructure requirements. Using state-of-the-art technology, the maximum distance between nodes is limited to hundreds of kilometers, necessitating multiple nodes to relay keys. For now, QKD Network (QKDN) relies on software-defined networking (SDN) and a central orchestrator, but this centralized approach has limitations. Hence, the main challenge is to select an efficient path between key relays to avoid communication failure. To address these challenges, a more distributed approach could be envisioned. In this paper, we propose to leverage one of the distributed routing protocols, OSPF, to redefine and improve the current architecture. We propose a novel QKDN-based OSPF (Open Shortest Path First) architecture for efficient key relay routing, offering a completely different dimension to the overall network management: we modify QKDN architecture to exploit the OSPF networks and present a QKD-enabled OSPF version capable of computing the best path for key relay, offering a cost-effective and scalable solution for widespread QKD adoption.
As an important support for quantum communication, quantum key distribution (QKD) networks have achieved a relatively mature level of development, and they face higher requirements for multi-user end-to-end networking capabilities. Thus, QKD networks need an effective management plane to control and coordinate with the QKD resources. As a promising technology, software defined networking (SDN) can separate the control and management of QKD networks from the actual forwarding of the quantum keys. This paper systematically introduces QKD networks enabled by SDN, by elaborating on its overall architecture, related interfaces, and protocols. Then, three-use cases are provided as important paradigms with their corresponding schemes and simulation performances.
Software-defined networking (SDN) has emerged as a promising paradigm for managing and controlling network resources efficiently. However, ensuring the security of data packets transmitted within an SDN environment remains a critical challenge. Traditional networking relies on static configurations, while SDN offers dynamic control and programmability, revolutionizing network management. In SDN, the application layer employs tools like OpenDaylight and Mininet for network management and testing. The control layer, managed by controllers such as Floodlight or ONOS, orchestrates traffic flow among switches. In the infrastructure layer, Quantum Key Distribution (QKD) with the BB84 protocol ensures secure communication. Together, these layers enable agile, programmable, and secure networking paradigms. This paper proposes integrating quantum key distribution (QKD) into SDN architectures to bolster packet-level security. By leveraging quantum entanglement and uncertainty, a secure communication channel between SDN controllers and switches is established, resilient to quantum attacks. Evaluation through simulations and real-world experiments demonstrates efficacy in mitigating security threats while minimizing overhead and latency, advancing SDN security IEEE 802.1X capabilities and leveraging quantum technologies for cybersecurity.
Quantum cryptography provides an effective approach to address the security challenges in communication network posed by Shor's factorization, Grover's search, and other new algorithms. We propose an architecture of QoS-oriented quantum key distribution network (QKDN) based on network slicing and software-defined network (SDN). The network slices with different QoS levels can be constructed according to users' requirements. The throughput, latency and other QoS metrics requirement can be obtained by allowing for centralized control management and more flexible resource allocation using the scheme of SDN. Simulation results show that slicing scheme in QKDN can flexibly orchestrate resources to meet QoS of the services and can also be easily integrated with existing communication networks.
Quantum Key Distribution (QKD) is a mechanism that allows two entities to agree on a secret key over a quantum channel. Recently, commercially viable QKD technology appeared on the market and the European Telecommunications Standards Institute (ETSI) established a working group to standardize QKD for commercial applications. Several testbeds and pre-commercial QKD networks are being deployed in the world, all requiring sophisticated control mechanisms to enable key exchanges between non-adjacent nodes for remote applications. In this paper, we implement and evaluate a prototype that realizes the architecture defined by ETSI and uses trusted relay nodes to exchange keys between non-adjacent nodes. In particular, we present the Software-Defined Network (SDN) Controller and the Software-Defined QKD nodes designed to control the QKD experimental testbed in Milan, named PoliQI. We test the proposed prototype in an emulation environment, showing its advantages in inter-datacenter communication scenarios in terms of key delivery time and application acceptance ratio.