# Blockchain-Assisted QoS-Aware Routing for Software-Defined Wide Area Network
## 1 Introduction  
Cloud computing has established a new computing era by providing IT resources (i.e., hardware, platforms, software, etc.) on an on-demand basis. Despite the potential gains of cloud computing over traditional IT, the network overhead and Quality of Service (QoS) aspects are still a major concern as the data are processed and stored in the computing resources located remotely. Alternatively, edge computing architecture provides a distributed computing environment where the local computing units are considered asa part of the edge. But edge computing may not always be a good choice for the scalable services that require massive, secure data storage, big data computing, etc. So, an effective way to access the available features of cloud computing is needed, and it is crucial to find a strategy to manage the movement of big data to/from cloud computing or for any interactive tasks to be executed in a cloud platform with assurance of satisfying Quality of Service (QoS) aspects. For example, a cloud user may need to download a very large file with a certain delay constraint, or a real-time application running in the cloud may require frequent interactions with the end-user device. Ensuring uninterrupted network services and effective network management necessitates the adoption of application-aware routing. This is imperative due to the varied Quality of Service (QoS) demands exhibited by different applications, including requirements for maximum bandwidth, minimal latency, etc. While one application might prioritize maximum bandwidth, another could emphasize minimal cost, but others may like to apply both with a certain weight. Furthermore, network conditions dynamically fluctuate in response to traffic and failures. Consequently, the adoption of application-aware routing becomes important as business applications often exhibit diverse network Quality of Service (QoS) needs. Each application possesses its own set of QoS characteristics to be satisfied by the cloud provider. Such QoS aspects are also highly related to the Service Level Agreements (SLAs) made for cloud-based services to the clients. So, the intermediary network also needs to consider explicit accounting for the distinct QoS characteristics requirements and fulfilling those requirements while facilitating the cloud service access to the end-users. In this regard, the traffic between end-user and the cloud provider needs to be classified depending on QoS requirements, and an asymmetric (or prioritized) treatment of such classified network packets by the intermediary network routers can result in solutions that are not only advantageous (such as potentially reducing expected network delay) to applications but can also be better suited to satisfy individual user preferences. For example, some customers may prioritize services that guarantee packet delivery even at a higher cost, while others might prefer more affordable options accepting less reliable data transfers. QoS-aware routing on the internet generally encompasses protocols designed to enable the prioritization of network traffic, taking into account parameters such as bandwidth, latency, jitter, reliability, etc. Various protocols and technologies have been employed for the implementation of QoS-aware routing, each exhibiting distinct advantages and limitations. Alternatively, SDN (Software-Defined Network) is a paradigm shift in network management and routing that provides better flexibility, efficiency, and programmability than classical networking systems. The importance of the software-defined wide area network (SD-WAN) over the traditional internet lies in its ability to dynamically optimize network traffic, prioritize critical applications, and ensure secure and efficient data transmission, offering unparalleled control and flexibility for modern enterprises. This research proposes a new QoS-aware routing algorithm for SD-WAN supporting multiple QoS together to ensure cloud service accessibility in a required manner.