Cloud Continuum and Cloud Federation for Scalable Distributed Applications

Cloud computing has evolved to meet the diverse needs of individuals, organizations, and industries, incorporating paradigms such as fog and edge computing. These paradigms aim to enhance efficiency in data management, resource allocation, and service delivery by mitigating issues like latency caused by centralized cloud infrastructures. This has led to the development of more distributed approaches that address specific application requirements, especially in latency-sensitive scenarios.

The Cloud Continuum (CC) refers to a cohesive integration of multiple computing layers, cloud, fog, edge, and IoT devices, working together to deliver services based on specific application requirements. It represents a vertical ecosystem that bridges centralized and decentralized computing environments, offering a seamless computing experience from cloud to edge. 

This continuum enables the deployment of services across various layers, ensuring better performance for latency-sensitive and data-intensive applications. Researchers emphasize that CC systems operate simultaneously across multiple tiers (cloud, fog, edge, and IoT), allowing more efficient and responsive service provisioning. Variations of this concept are known as cloud-to-edge, edge-to-cloud, or fog-to-cloud continuum systems. In practice, the CC is recognized as a dynamic and hierarchical environment where applications can exploit the most suitable layer for their specific needs.

On the other hand, Cloud Federation (CF) is defined as a horizontal integration model that enables multiple cloud providers to collaborate by sharing resources, services, and infrastructures. The National Institute of Standards and Technology (NIST) and the IEEE SIIF standard describe CF as a framework to ensure interoperability, resource sharing, and unified service access across different cloud providers. Each provider in a federated system may differ in architecture, service offerings, policies, and pricing, but collectively, they present a unified environment to end users.

CF supports the idea of a multi-cloud ecosystem where users can seamlessly access services from various providers. It enhances user experience by leveraging the unique strengths of different cloud environments, improving scalability, performance, and fault tolerance. In this work, CF is categorized as a system that operates across different domains, connecting isolated cloud infrastructures into a federated, collaborative environment.

Integrating CC and CF offers significant potential for improving resource optimization, scalability, and service delivery. Combining these models allows for seamless orchestration across both vertical layers (from edge to cloud) and horizontal domains (across clouds). This integration is particularly valuable in heterogeneous and dynamic environments like IoT ecosystems, where diverse applications may have conflicting or complex requirements.

However, this integration presents many challenges. Researchers have identified several of these, including:

• Ensuring interoperability between different cloud and edge platforms
• Addressing security, trust, and privacy in distributed environments
• Managing data governance and compliance in a federated setting
• Considering economic aspects when a cloud system uses partner resources
• Overcoming architectural complexities due to diverse technologies and policies

The convergence of CC and CF promises a robust infrastructure that can dynamically adapt to modern computing demands. While the CC enables vertical integration of resources from edge to cloud, CF fosters horizontal cooperation among different providers. Their integration could transform how services are developed, deployed, and consumed, but achieving this vision will require overcoming significant technical and organizational challenges.
 

References

[1] L. Bittencourt, R. Immich, R. Sakellariou, N. Fonseca, E. Madeira, M. Curado, L. Villas, L. DaSilva, C. Lee, O. Rana, The Internet of Things, Fog and Cloud Continuum: Integration and Challenges, Internet of Things 3–4 (2018) 134–155. doi:10.1016/j.iot.2018.09.005.

[2] S. Moreschini, F. Pecorelli, X. Li, S. Naz, D. Hastbacka, D. Taibi, Cloud Continuum: The Definition, IEEE Access 10 (2022) 131876–131886. doi:10.1109/access.2022.3229185.

[3] S. Dustdar, V. C. Pujol, P. K. Donta, On Distributed Computing Continuum Systems, IEEE Transactions on Knowledge and Data Engineering 35 (4) (2023) 4092–4105. doi:10.1109/tkde.2022.3142856.

[4] P. Gkonis, A. Giannopoulos, P. Trakadas, X. Masip-Bruin, F. D’Andria, A Survey on IoT-Edge-Cloud Continuum Systems: Status, Challenges, Use Cases, and Open Issues, Future Internet 15 (12) (2023) 383. doi:10.3390/fi15120383.

[5] C. A. Lee, R. B. Bohn, M. Michel, The NIST Cloud Federation Reference Architecture, 2020. doi:10.6028/nist.sp.500-332.

[6] R. B. Bohn, C. A. Lee, IEEE Standard for Intercloud Interoperability and Federation (SIIF), IEEE Std 2302-2021 (2022) 1–42. doi:10.1109/IEEESTD.2022.9732072.

[7] L. Chouhan, P. Bansal, B. Lauhny, Y. Chaudhary, A Survey on Cloud Federation Architecture and Challenges, Springer Singapore, 2020, pp. 51–65. doi:10.1007/978-981-15-2071-6_5.

[8] J. Santos, T. Wauters, B. Volckaert, F. De Turck, Towards Low-Latency Service Delivery in a Continuum of Virtual Resources: State-of-the-Art and Research Directions, IEEE Communications Surveys Tutorials 23 (4) (2021) 2557–2589. doi:10.1109/COMST.2021.3095358.

[9] A. Maia, A. Boutouchent, Y. Kardjadja, M. Gherari, E. G. Soyak, M. Saqib, K. Boussekar, I. Cilbir, S. Habibi, S. O. Ali, W. Ajib, H. Elbiaze, O. Erçetin, Y. Ghamri-Doudane, R. Glitho, A Survey on Integrated Computing, Caching, and Communication in the Cloud-to-Edge Continuum, Computer Communications 219 (2024) 128–152. doi: 10.1016/j.comcom.2024.03.005.

[10] J. Alonso, L. Orue-Echevarria, V. Casola, A. I. Torre, M. Huarte, E. Osaba, J. L. Lobo, Understanding the Challenges and Novel Architectural Models of Multi-Cloud Native Applications – A Systematic Literature Review, Journal of Cloud Computing 12 (1) (Jan. 2023). doi:10.1186/s13677-022-00367-6.

[11] J. Alonso, L. Orue-Echevarria, M. Huarte, Cloudops: Towards the Operationalization of the Cloud Continuum: Concepts, Challenges, and a Reference Framework, Applied Sciences 12 (9) (2022) 4347. doi:10.3390/app12094347.