Review of SDN-based load-balancing methods, issues, challenges, and roadmap

The development of the Internet and smart end systems, such as smartphones and portable laptops, along with the emergence of cloud computing, social networks, and the Internet of Things, has brought about new network requirements. To meet these requirements, a new architecture called software-defined network (SDN) has been introduced. However, traffic distribution in SDN has raised challenges, especially in terms of uneven load distribution impacting network performance. To address this issue, several SDN load balancing (LB) techniques have been developed to improve efficiency. This article provides an overview of SDN and its effect on load balancing, highlighting key elements and discussing various load-balancing schemes based on existing solutions and research challenges. Additionally, the article outlines performance metrics used to evaluate these algorithms and suggests possible future research directions

Measurement-Driven Algorithm and System Design for Wireless and Datacenter Networks

The growing number of mobile devices and data-intensive applications pose unique challenges for wireless access networks as well as datacenter networks that enable modern cloud-based services. With the enormous increase in volume and complexity of traffic from applications such as video streaming and cloud computing, the interconnection networks have become a major performance bottleneck. In this thesis, we study algorithms and architectures spanning several layers of the networking protocol stack that enable and accelerate novel applications and that are easily deployable and scalable. The design of these algorithms and architectures is motivated by measurements and observations in real world or experimental testbeds. In the first part of this thesis, we address the challenge of wireless content delivery in crowded areas. We present the AMuSe system, whose objective is to enable scalable and adaptive WiFi multicast. AMuSe is based on accurate receiver feedback and incurs a small control overhead. This feedback information can be used by the multicast sender to optimize multicast service quality, e.g., by dynamically adjusting transmission bitrate. Specifically, we develop an algorithm for dynamic selection of a subset of the multicast receivers as feedback nodes which periodically send information about the channel quality to the multicast sender. Further, we describe the Multicast Dynamic Rate Adaptation (MuDRA) algorithm that utilizes AMuSe's feedback to optimally tune the physical layer multicast rate. MuDRA balances fast adaptation to channel conditions and stability, which is essential for multimedia applications. We implemented the AMuSe system on the ORBIT testbed and evaluated its performance in large groups with approximately 200 WiFi nodes. Our extensive experiments demonstrate that AMuSe can provide accurate feedback in a dense multicast environment. It outperforms several alternatives even in the case of external interference and changing network conditions. Further, our experimental evaluation of MuDRA on the ORBIT testbed shows that MuDRA outperforms other schemes and supports high throughput multicast flows to hundreds of nodes while meeting quality requirements. As an example application, MuDRA can support multiple high quality video streams, where 90% of the nodes report excellent or very good video quality. Next, we specifically focus on ensuring high Quality of Experience (QoE) for video streaming over WiFi multicast. We formulate the problem of joint adaptation of multicast transmission rate and video rate for ensuring high video QoE as a utility maximization problem and propose an online control algorithm called DYVR which is based on Lyapunov optimization techniques. We evaluated the performance of DYVR through analysis, simulations, and experiments using a testbed composed of Android devices and o the shelf APs. Our evaluation shows that DYVR can ensure high video rates while guaranteeing a low but acceptable number of segment losses, buffer underflows, and video rate switches. We leverage the lessons learnt from AMuSe for WiFi to address the performance issues with LTE evolved Multimedia Broadcast/Multicast Service (eMBMS). We present the Dynamic Monitoring (DyMo) system which provides low-overhead and real-time feedback about eMBMS performance. DyMo employs eMBMS for broadcasting instructions which indicate the reporting rates as a function of the observed Quality of Service (QoS) for each UE. This simple feedback mechanism collects very limited QoS reports which can be used for network optimization. We evaluated the performance of DyMo analytically and via simulations. DyMo infers the optimal eMBMS settings with extremely low overhead, while meeting strict QoS requirements under different UE mobility patterns and presence of network component failures. In the second part of the thesis, we study datacenter networks which are key enablers of the end-user applications such as video streaming and storage. Datacenter applications such as distributed file systems, one-to-many virtual machine migrations, and large-scale data processing involve bulk multicast flows. We propose a hardware and software system for enabling physical layer optical multicast in datacenter networks using passive optical splitters. We built a prototype and developed a simulation environment to evaluate the performance of the system for bulk multicasting. Our evaluation shows that the optical multicast architecture can achieve higher throughput and lower latency than IP multicast and peer-to-peer multicast schemes with lower switching energy consumption. Finally, we study the problem of congestion control in datacenter networks. Quantized Congestion Control (QCN), a switch-supported standard, utilizes direct multi-bit feedback from the network for hardware rate limiting. Although QCN has been shown to be fast-reacting and effective, being a Layer-2 technology limits its adoption in IP-routed Layer 3 datacenters. We address several design challenges to overcome QCN feedback's Layer- 2 limitation and use it to design window-based congestion control (QCN-CC) and load balancing (QCN-LB) schemes. Our extensive simulations, based on real world workloads, demonstrate the advantages of explicit, multi-bit congestion feedback, especially in a typical environment where intra-datacenter traffic with short Round Trip Times (RTT: tens of s) run in conjunction with web-facing traffic with long RTTs (tens of milliseconds)

OSMOSIS: Enabling Multi-Tenancy in Datacenter SmartNICs

Multi-tenancy is essential for unleashing SmartNIC's potential in datacenters. Our systematic analysis in this work shows that existing on-path SmartNICs have resource multiplexing limitations. For example, existing solutions lack multi-tenancy capabilities such as performance isolation and QoS provisioning for compute and IO resources. Compared to standard NIC data paths with a well-defined set of offloaded functions, unpredictable execution times of SmartNIC kernels make conventional approaches for multi-tenancy and QoS insufficient. We fill this gap with OSMOSIS, a SmartNICs resource manager co-design. OSMOSIS extends existing OS mechanisms to enable dynamic hardware resource multiplexing on top of the on-path packet processing data plane. We implement OSMOSIS within an open-source RISC-V-based 400Gbit/s SmartNIC. Our performance results demonstrate that OSMOSIS fully supports multi-tenancy and enables broader adoption of SmartNICs in datacenters with low overhead.Comment: 12 pages, 14 figures, 103 reference

Contributions to routing scalability and QoS assurance in cloud data transport networks based on the recursive internetwork architecture

With an increasing number of devices and heterogeneous distributed applications, it is becoming evident that service delivered by the current Internet fall short to supply the actual Quality of Service (QoS) requirements of applications. In addition, the global scope of the IP layer causes large scalability problems on the network. Multiple solutions aim to overcome the limitations of the model (BGP, NAT, etc.), but all end being constrained by the same networking model that they try to improve, ending simply breaking and patching the stack itself of TCP/IP. In contrast, RINA proposes a new clean-slate Internet architecture based on a recursive networking stack with focus on inter process communication, where each layer, or DIF, performs the same set of tasks. DIFs are fully configurable by mean of programmable policies, and provide complete support for QoS services. RINA is capable to provide a standardized way to express the capabilities of each layer, the QoS Cubes. With those, RINA allows for applications and upper processes to express their requirements in terms of latency, losses, etc. The contributions in this thesis take profit from the recursive stack of RINA and the use of policies to propose and analyse old and new solutions which would not be compatible with the current TCP/IP Internet. Improving the QoS services, this work takes profit from the information on requirements provided by the applications themselves to improve the assurance of QoS. With the use of Q-based scheduling policies, improved QoS assurances are provided, aiming to provide “good enough” service for all flows in the network, resulting in a more appropriate sharing of resources. These policies have been tested in backbone-like networks, showing interesting improvements with respect to commonly used solutions like MPLS-based VPNs. In addition the provisioning of QoS services to end-users is also considered. In order to allow that, it is required to impose some limits on what end-users can send to the network, limiting the amount of priority traffic that potentially greedy users can send. In that regard, while enforcing strict rate-limits per QoS would be trivial in RINA, a new △Q-based rate-limiting policy that aims to limit the amount of priority traffic in a more user-friendly way is also explored. In terms of scalability, this work also considers different measures to improve forwarding and routing within large-scale networks. As for the use of policies that could profit from specific network topologies, a new forwarding policy, that mix both topological rules and exceptions, is proposed. With this policy, forwarding table lookups in large tables are replaced with fast and simple forwarding rules based on the location of nodes and their neighbourhood. Given the common topologies used in large data centres, the proposed policy is found to be a perfect match for those scenarios. Test for different data centre topology showed clear improvements, requiring only a small fraction of all forwarding information despite the large size of such networks, depending that in the number of concurrent failures in the network rather than on the size of it. In addition, this work also considers the use of topological routing policies to populate exceptions upon failures. The use of topological routing solutions resulted in reduced complexity for computing paths and less routing messages. In addition to topological solutions, the use other routing solution, not well suited for the IP environment are also investigated. Specifically, it is shown how a Landmark routing solution could be implemented within RINA. Finally, efforts are also devoted to analyse the importance of path selection for ensuring QoS requirements and how it is not required to reach extremes solutions, like the use of connections, to provide the required services.Con un número cada vez mayor de dispositivos y aplicaciones distribuidas, se está volviendo evidente que el servicio best-effort ofrecido por la actual Internet TCP/IP no satisface los requisitos de calidad de servicio (QoS) de las aplicaciones. No solo eso, sino que el alcance global de la capa de IP se convierte en la causa de grandes problemas de escalabilidad, requiriendo costes cada vez más altos para ser resueltos. Desde la implantación de TCP/IP, han aparecido múltiples soluciones que tienen como objetivo superar las limitaciones del modelo (BGP, NAT, LISP, etc.). Aun así, todas estas soluciones terminan restringidas por el mismo modelo de red que intentan mejorar. Dado esto, la mayoría de las soluciones terminan simplemente rompiendo y parcheando la pila misma de TCP/IP. Con el objetivo de resolver esos problemas, la Recursive InterNetwork Architecture (RINA) propone una nueva arquitectura de Internet que vuelve a las raíces de la comunicación en red. En lugar de parchear la pila actual de TCP/IP, RINA propone una pila de red recursiva con enfoque en la comunicación entre procesos, donde cada capa, llamada Distributed IPC Facility (DIF), realiza el mismo conjunto de tareas. Mientras realizan las mismas tareas, las DIF de RINA son completamente configurables por medio de políticas programables, definiciones de cómo realizar tales tareas. Además, RINA brinda soporte completo para servicios de QoS por medio de los Cubos QoS, o clases de QoS que definen las capacidades de cada DIF. Con el uso de los Cubos QoS, RINA es capaz de proporcionar una forma estandarizada de expresar las capacidades de cada capa. Además, dada esa información, RINA también permite que las aplicaciones y los procesos de capas superiores expresen sus requisitos de QoS en términos de latencia aceptada, pérdidas, uso promedio, etc. Las contribuciones en esta tesis sacan provecho de la pila recursiva de RINA y el uso de políticas para proponer y analizar soluciones, antiguas y nuevas, para QoS y escalabilidad, que no serán compatibles con la Internet TCP/IP actual. En términos de mejoras de los servicios de QoS, el trabajo en esta tesis aprovecha la información sobre los requisitos de flujo, proporcionados por las propias aplicaciones, para mejorar las garantías de QoS proporcionadas por la red. Propone el uso de políticas basadas en △Q, proporcionando garantías de QoS mejoradas, que coinciden mejor con los requisitos de los flujos. A diferencia de las soluciones de diferenciación de QoS más simples, donde los servicios de QoS se proporcionan en orden de prioridad, △Q pretende proporcionar un servicio “suficientemente bueno" para todos los flujos en la red, lo que resulta en una repartición de recursos más apropiada. En este trabajo, estas políticas se han probado en redes tipo backbone, que muestran mejoras interesantes con respecto a las soluciones comunes de diferenciación de QoS, como las VPN basadas en MPLS. Además del uso de las políticas de △Q en el núcleo de la red, esta tesis también considera el suministro de servicios de QoS a los usuarios finales, siendo ese el objetivo final de las redes. Para permitir eso, se requiere imponer algunos límites a lo que los usuarios finales pueden enviar a la red, con el fin de limitar la cantidad de tráfico prioritario que usuarios codiciosos puedan enviar. En ese sentido, aunque imponer límites de velocidad estrictos por QoS sería trivial en RINA, también se explora una nueva política de limitación de tasas basada en △Q que pretende limitar la cantidad de tráfico prioritario de una manera más beneficiosa para los usuarios. En términos de escalabilidad, esta tesis también considera diferentes medidas para mejorar el reenvío y el enrutamiento dentro de redes de gran escala. Primero, en cuanto al uso de políticas que podrán beneficiarse de topologías de red específicas, se propone una nueva política de forwarding que combina reglas topológicas, es decir decisiones basadas en la ubicación de nodos, y excepciones, es decir entradas que sobrescriben reglas en caso de error. Con esta política, las costosas búsquedas en tablas grandes se reemplazan con reglas de rápidas y simples basadas en la ubicación de los nodos y su vecindad. Dadas las topologías específicas más comúnmente utilizadas en los grandes centros de datos hoy en día, se encuentra que el uso de la política propuesta es la combinación perfecta para esos escenarios. Pruebas en varias topologías comunes para centros de datos mostraron mejoras claras, que requieren solo una pequeña fracción de toda la información sobre la red, a pesar del gran tamaño de dichas redes, dependiendo esta de la cantidad de fallas concurrentes en la red y no del tamaño de la misma. Además, esta tesis también considera el uso de políticas de enrutamiento topológico para poblar tales excepciones en caso de fallas. El uso de soluciones de enrutamiento topológico dio como resultado la reducción de la complejidad en el cálculo de rutas, junto con un menor número de mensajes de enrutamiento. Además de las soluciones topológicas, también se investiga el uso de otra solución de enrutamiento, no adecuada para el entorno de IP. Específicamente, se muestra como una solución de enrutamiento Landmark, una solución de enrutamiento de la familia de enrutamiento compacto, podría implementarse dentro de RINA. Finalmente, también se dedican esfuerzos a analizar la importancia de la selección de rutas para garantizar los requisitos de QoS y como no se requiere llegar a soluciones extremas, como el uso de conexiones, para proporcionar los servicios requeridos.Postprint (published version

End-user traffic policing for QoS assurance in polyservice RINA networks

Looking at the ever-increasing amount of heterogeneous distributed applications supported on current data transport networks, it seems evident that best-effort packet delivery falls short to supply their actual needs. Multiple approaches to Quality of Service (QoS) differentiation have been proposed over the years, but their usage has always been hindered by the rigidness of the TCP/IP-based Internet model, which does not even allow for applications to express their QoS needs to the underlying network. In this context, the Recursive InterNetwork Architecture (RINA) has appeared as a clean-slate network architecture aiming to replace the current Internet based on TCP/IP. RINA provides a well-defined QoS support across layers, with standard means for layers to inform of the different QoS guarantees that they can support. Besides, applications and other processes can express their flow requirements, including different QoS-related measures, like delay and jitter, drop probability or average traffic usage. Greedy end-users, however, tend to request the highest quality for their flows, forcing providers to apply intelligent data rate limitation procedures at the edge of their networks. In this work, we propose a new rate limiting policy that, instead of enforcing limits on a per QoS class basis, imposes limits on several independent QoS dimensions. This offers a flexible traffic control to RINA network providers, while enabling end-users freely managing their leased resources. The performance of the proposed policy is assessed in an experimental RINA network test-bed and its performance compared against other policies, either RINA-specific or adopted from TCP/IP. Results show that the proposed policy achieves an effective traffic control for high QoS traffic classes, while also letting lower QoS classes to take profit of the capacity initially reserved for the former ones when available.Peer ReviewedPostprint (author's final draft