Distributed Control Plane Research Articles

Synthesis of Fault-Tolerant Distributed Router Configurations

Operators of modern networks require support for diverse and complex end-to-end policies, such as, middlebox traversals, isolation, and traffic engineering. While Software-defined Networking (SDN) provides centralized custom routing functionality in networks to realize these policies, many networks still deploy "legacy" control planes running distributed routing protocols like OSPF and BGP because these protocols are scalable and robust to failures. However, realization of policies by distributed control plane configurations is manual and error-prone. We present Zeppelin, a system for automatically generating policy-compliant control planes that also behave well under majority of small network failures. Zeppelin differs from existing approaches in that it uses policy-compliant paths to guide the synthesis process instead of directly generating policy-compliant configurations. We show that Zeppelin synthesizes highly resilient and policy-compliant configurations for real topologies with up to 80 routers.

A Novel Software-Defined Networking Controller: the Distributed Active Information Model (DAIM)

This paper presents a new OpenFlow controller: the Distributed Active Information Model (DAIM). The DAIM controller was developed to explore the viability of a logically distributed control plane. It is implemented in a distributed way throughout a software-defined network, at the level of the switches. The method enables local process flows, by way of local packet switching, to be controlled by the distributed DAIM controller (as opposed to a centralised OpenFlow controller). The DAIM ecosystem is discussed with some sample code, together with flowcharts of the implemented algorithms. We present implementation details, a testing methodology, and an experimental evaluation. A performance analysis was conducted using the Cbench open benchmarking tool. Comparisons were drawn with respect to throughput and latency. It is concluded that the DAIM controller can handle a high throughput, while keeping the latency relatively low. We believe the results to date are potentially very interesting, especially in light of the fact that a key feature of the DAIM controller is that it is designed to enable the future development of autonomous local flow process and management strategies.

Synthesis of Fault-Tolerant Distributed Router Configurations

Operators of modern networks require support for diverse and complex end-to-end policies, such as, middlebox traversals, isolation, and traffic engineering. While Software-defined Networking (SDN) provides centralized custom routing functionality in networks to realize these policies, many networks still deploy "legacy" control planes running distributed routing protocols like OSPF and BGP because these protocols are scalable and robust to failures. However, realization of policies by distributed control plane configurations is manual and error-prone. We present Zeppelin, a system for automatically generating policy-compliant control planes that also behave well under majority of small network failures. Zeppelin differs from existing approaches in that it uses policy-compliant paths to guide the synthesis process instead of directly generating policy-compliant configurations. We show that Zeppelin synthesizes highly resilient and policy-compliant configurations for real topologies with up to 80 routers.

Scalable orchestration of software defined service overlay network for multipath transmission

Multipath transmission on overlay network is proved to effectively improve transmission quality for Internet applications requiring stringent QoS guarantees, e.g., real-time conversational applications. The orchestration of overlay nodes is the basis of overlay multipath transmission, which fundamentally impacts the management, control and transmission quality of overlay network. In this paper, we introduce SDN (Software Defined Networking) paradigm to orchestrate overlay nodes for optimal global management and intelligent forwarding control and we name the overlay multipath framework Software Defined Service Overlay Network (SDSON). To achieve efficient and reliable orchestration of nodes in SDSON, we focus on two major challenges, 1) the match between overlay and underlay networks for reducing the transmission quality degradation from the uncertainty of overlay paths, 2) the enhancement of scalability for eliminating control plane bottleneck of SDSON centralized structure. Correspondingly, we propose a scalable overlay orchestration structure. 1) coordinate-based global topology view of overlay nodes is employed to characterize and constrain relationships between overlay nodes. Coordinates are generated by using MDS-MAP to convert measured delays. And a balanced-binary-tree measure method is designed to balance measure loads. 2) The two-level distributed control plane is designed by decoupling control and management functions in control plane and together a novel collaborative control mechanism. The first level focuses on global management and the second concentrates on conducting global control with the collaborative control mechanism among distributed controllers. We use modified ISODATA with density-based initialization improvement to partition global topology view into distributed sub-domains, which are governed by controllers composing the second level control plane. Evaluations on OMNeT++ demonstrate that coordinate-based view matches well with practical underlay networks, sub-domains partition quality outperforms classical algorithms, and the scalable control planes with collaborative control mechanism alleviate control pressure and improve control performance efficiently.

On detecting compromised controller in software defined networks

While traditional networks depend on a fully distributed control plane, Software Defined Networks (SDNs), the rapidly emerging area in computer networking, utilize a centralized control plane. SDNs bring in many benefits such as fine-grained control, possibility of optimal routing, and resource management within the network. As a result, SDNs find wider deployments in certain segments of networking such as data center networks. In addition, SDN approach is a potential candidate for the control plane design in 5G networks. Despite the benefits, SDNs face certain issues such as the possibility of single point failure, the communication overhead between switches and controllers, and more importantly the security as well as trustability of the control plane. Due to the centralized nature of the control plane, it is important to detect the presence of compromised control plane in an SDN. Compromised control plane refers to the situation where one or more of the controllers in an SDN are compromised by malwares, resulting in deviation from the normal control plane behavior. Developing new solutions for detecting the presence of compromised controllers is exacerbated by the lack of appropriate SDN traffic data sets. As a result, existing literature lacks solutions to detect the presence of a compromised control plane. Of particular interest is the case where SDN controller-specific threats hide their presence from end-users and administrators of the network.Our contributions in this paper include the following: (i) identification of five threat vectors that represent compromised controllers in SDNs, (ii) creation of a large volume of OpenFlow traffic traces in order for studying various SDN threat vectors, (iii) proposal of nine novel OpenFlow-specific features that capture the above mentioned threat vectors, and (iv) study of machine-learning based detection technique for compromised control plane using six classifiers. The OpenFlow traffic trace data set, we created, is made available for the use of larger research community. We carried out detailed experimental studies that show the efficacy of our scheme in detecting the presence of compromised controllers. Our results indicate that Random Forest is the most suitable machine learning classifier that provides about 97% accuracy.

An Efficient Energy Conservation Dynamic Consistency Algorithm for SDN Control Plane

Centralized control, the main idea of SDN (Software-Defined Networking) to simplify the control flow, may make SDN suffer from performance bottlenecks. Therefore, we need to use a distributed control plane to overcome the problem. But there are also consistency problem in distributed control plane of SDN. In this paper, we first quantize the consistency, communication costs and availability with relevant research of SDN distributed control plane. Secondly, by normalized calculation, we find the relationship between them. Then we propose a dynamic consistency algorithm for the control plane of SDN. Finally, we corroborate the validity of the algorithm by some experiments. The experimental results show that the proposed algorithm can effectively improve the plane consistency of SDN control.

Performance Evaluation and Optimization of Hierarchical Routing in SDN Control Plane

In Software defined networking (SDN), distributed control plane is becoming a promising solution to tackle with scalability and performance. We propose a tree-like hierarchical routing architecture which employs the divide-and-conquer strategy to enhance routing performance on the distributed control plane. To evaluate and optimize the performance of the hierarchical architecture, we apply queuing theory to modeling routing request arrival and processing, and derive an explicit expression of the routing response time. Then we formulate the resource allocation problem in the hierarchical architecture as an optimization problem whose objective is to minimize the response time subject to queue stability and resource constraints. Using the Karush- Kuhn-Tucker (KKT) condition we obtain the optimal resource allocation policy. Based on that, we theoretically prove that the response time under the hierarchical routing architecture is strictly less than that under the Peer to peer (P2P) architecture. Finally, we perform numerical analyses to confirm the conclusions.

Economic Viability of Software Defined Networking (SDN)

Economical and operational facets of networks drive the necessity for significant changes towards fundamentals of networking architectures. Recently, the momentum of programmable networking attempts illustrates the significance of economic aspects of network technologies. Software Defined Networking (SDN) has got the attention of researchers from both academia and industry as a means to decrease network costs and generate revenue for service providers due to features it promises in networking. In this article, we investigate how programmable network architectures, i.e. SDN technology, affect the network economics compared to traditional network architectures, i.e. MPLS technology. We define two metrics, Unit Service Cost Scalability and Cost-to-Service, to evaluate how SDN architecture performs compared to MPLS architecture. Also, we present mathematical models to calculate certain cost parts of a network. In addition, we compare different popular SDN control plane models, Centralized Control Plane (CCP), Distributed Control Plane (DCP), and Hierarchical Control Plane (HCP), to understand the economic impact of them with regards to the defined metrics. We use video traffic with different patterns for the comparison. This work aims at being a useful primer to providing insights regarding which technology and control plane model are appropriate for a specific service, i.e. video, for network owners to plan their investments.

Scalable distributed control plane for On-line social networks support cognitive neural computing in software defined networks

Though most of the current proposed distributed control planes maintain strong consistency among their controllers, this paper argues the strong consistency is not a prerequisite and proposes an Event Coordination System (ECS) that enables an efficient event replaying system and a distributed control plane (DisCon) using this event replaying system to construct eventually consistent global network topologies among its controllers without sacrificing scalability. Our ECS implements a novel request handling procedure that ensures a firstly received write request is firstly multi-casted, notified, and updated, so thus our DisCon can maximally ensure the same time sequence in which topology events get updated at different controllers and the constructed topologies can reflect the real network change in practice. We highlight the major mechanisms used, discuss the major causes of this eventual consistency, estimate the inconsistency window among controllers, and show how this eventual consistency does not make a big difference in supporting network applications. Experiments are conducted to evaluate our ECS and DisCon. The results show our DisCon has a larger event replay throughput and a lower event converging delay than HyperFlow, and larger flow setup rate and lower flow setup delay than most of the current distributed control planes.

Online Load Balancing for Distributed Control Plane in Software-Defined Data Center Network

Distributed control plane is a common approach to improve the scalability of software-defined data center networks. However, learning how to balance the load among the controllers remains a difficult problem, since the flows in the network fluctuate frequently. In this paper, we propose an online controller load balancing (OCLB) scheme to address this issue. We first formulate the load balancing problem as an optimization problem to minimize the average controller response time. Then we decompose it into a sequence of switch migrations, with each migration aiming to reduce the average response time as much as possible based on the realtime request distribution. An OCLB algorithm is designed based on the derived optimality and termination conditions of switch migration, and is proved to be near optimal with a bounded competitive ratio. Evaluations demonstrate that our scheme can achieve near-optimal load balancing among the control plane in an online manner.

SigMA: Signaling Framework for Decentralized Network Management Applications

The management of network infrastructures has become increasingly complex over time, which is mainly attributed to the introduction of new functionality to support emerging services and applications. To address this important issue, research efforts in the last few years focused on developing software-defined networking solutions. While initial work proposed centralized architectures, their scalability limitations have led researchers to investigate a distributed control plane. Controller placement algorithms and mechanisms for building a logically centralized network view are some examples of challenges addressed in this context. A critical issue that requires specific attention concerns the communication between distributed entities involved in decision-making processes. To this end, we propose SigMA, a signaling framework that supports communication between the different entities of a decentralized management and control system. We also define the communication primitives and interfaces involved in such a decentralized environment. The benefits of SigMA are illustrated through three realistic network resource management use cases with different communication requirements. Based on simulation, we demonstrate the flexibility and extensibility of our solution in satisfying these requirements, thus effectively supporting advanced decentralized decision-making processes.

Revisiting FiWi: On the Merits of a Distributed Upstream Resource Allocation Scheme

To improve fiber-wireless (FiWi) access network performance, this work proposes a distributed control plane by simply shifting the centralized control task away from the distant central office (optical plane) towards the closely clustered wireless nodes (wireless plane) at the access end. This distributed scheme results in a globally optimized upstream resource allocation scheme, thus paving the way for improved performance.

Maximizing SDN control resource utilization via switch migration

Software-Defined Networking is challenged by load imbalance of distributed control plane that is statically mapped to data plane. In this article, we design a scalable control mechanism via switch migration locally to maximize control resource utilization, and we define this problem as Switch Migration Problem (SMP). First, due to the various demands on controller CPU, bandwidth and memory for different switch, we provide a resource consuming model for SDN that takes the switches as the resource consumers and controllers as the resource providers. Then SMP is reduced to a network utilization maximization problem which is a typical combinational problem. Second, we introduce a synthesizing distributed algorithm to solve SMP — Distributed Hopping Algorithm (DHA), to disperse the calculations among the controllers involved. Finally, we implement a proof-of-concept for DHA based on Beacon controller, called DHA-CON, and the results are corroborated by several numerical simulations.

Flow Stealer: lightweight load balancing by stealing flows in distributed SDN controllers

Software-defined networking (SDN) introduces centralized controllers to increase network programmability drastically. Distributed control planes, in which multiple SDN controllers work together to manage a network, have been proposed to satisfy the requirements of large-scale networks, and different kinds of load-balancing approaches have been proposed to balance the workloads among these controllers. Current load-balancing approaches generally use switch migration, which adjusts the mapping between switches and controllers dynamically according to controller workloads. These switch migration-based approaches face challenges under burst traffic as a result of their overhead and longer detection periods. This paper proposes Flow Stealer, a lightweight load-balancing method for distributed SDN controllers. Flow Stealer uses a low-cost flow-stealing method, in which idle controllers share workloads temporarily with overloaded controllers by stealing flow events from them. The flow-stealing method not only can react to changes of network traffic more quickly, but can also reduce the frequency of switch migration. In addition, Flow Stealer incorporates both flow stealing and switch migration to adapt to burst traffic and long-term traffic changes. Experimental results show that Flow Stealer can balance the workloads among controllers more efficiently, especially under burst traffic.

Active synchronization of multi‐domain controllers in software‐defined networks

SummaryMulti‐domain multi‐controller software‐defined networks have an inevitable potential to improve the scalability and reliability of massive data center networks because the single controller cannot match the rapid expansion of cloud computing. The inconsistency among controllers can significantly degrade the network performance, because of that the data center network in software‐defined networks has physically distributed control plane but operates with logically centralized plane. Existing synchronization among multi‐controllers is based on the periodic synchronization (PS) that is stiffly triggered by time. However, the PS neglects potential inconsistency and further produces much packet loss and poor load balance in the whole network. Longer synchronization period increases synchronization overhead and decreases network performance. To keep the load consistency among controllers, we propose an active synchronization algorithm that is agilely triggered by event, ie, synchronization is triggered when the load of specific server exceeds the average load of its domain. With such an event triggered mechanism, we cannot only eliminate the correlation between synchronization and time but also avoid forwarding loop in the global network. Simulation results show that compared to existing PS‐based schemes, our active synchronization algorithm can achieve better load balance with less synchronization overhead and lower packet loss rate.

An East-West interface for distributed SDN control plane: Implementation and evaluation

Software Defined Networking (SDN) is a new concept within the networking field that allows programmability, automation, agility of services, and innovation using physically or logically centralized controllers. However, there is a lack of SDN in broadly distributed domains, where each domain has its own Controller. In this paper, we propose and implement a Communication Interface for Distributed Control plane (CIDC) that allows synchronization, the exchange of notifications as well as services between multiple distributed SDN Controllers. We have implemented distributed services such as Firewall and Load Balancer to improve the security and overall quality of service in distributed SDN architecture. The proposal for this research was evaluated in real wide-area network topologies, and the results show the feasibility of our CIDC in term of performance compared to the previous models based on a set of controllers arranged in a cluster.

A multipath resource updating approach for distributed controllers in software-defined network

Finding effective ways to collect the usage of network resources in all kinds of applications to ensure a distributed control plane has become a key requirement to improve the controller’s decision making performance. This paper explores an efficient way in combining dynamic NetView sharing of distributed controllers with the behavior of intra-service resource announcements and processing requirements that occur in distributed controllers, and proposes a rapid multipathing distribution mechanism. Firstly, we establish a resource collecting model and prove that the prisoner’s dilemma problem exists in the distributed resource collecting process in the Software-defined Network (SDN). Secondly, we present a bypass path selection algorithm and a diffluence algorithm based on Q-learning to settle the above dilemma. At last, simulation results are given to prove that the proposed approach is competent to improve the resource collecting efficiency by the mechanism of self-adaptive path transmission ratio of our approach, which can ensure high utilization of the total network we set up.

A game-theoretic approach to elastic control in software-defined networking

Elastic control could balance the distributed control plane in Software-Defined Networking (SDN). Dynamic switch migration has been proposed to achieve it. However, existing schemes mainly focus on how to execute migration operation, but not why. This paper designs a decision-making mechanism based on zero-sum game theory to reelect a new controller as the master for migrated switches. It first chooses a switch for migration in the heavy controller which invites its neighbors as the game players to compete for the master role of this switch in the game-playing field (GPF) which is an occasional and loose domain for game-playing. Second, based on the concept of GPF, we design a decentralized strategy to play the game and determine which player as the final master. We implement it by extending the OpenFlow protocol. Finally, numerical results demonstrate that our distributed strategy can approach elastic control plane with better performance.

Distributed meta-scheduling in lambda grids by means of Ant Colony Optimization

Data transport infrastructures based on wavelength-routed optical networks are appealing to the grid community because they can provide a reconfigurable and high-bandwidth network service to emerging data-intensive grid applications. Traditionally, the control plane of those optical networks is independent from the management of other resources, such as computing systems, and it is commonly limited to fulfill immediate reservation demands of lightpaths. However, the lack of network integration to grid resources and the absence of advance reservation of bandwidth are critical aspects to the widespread adoption of optical networks in grid environments. Therefore, in this work, a distributed grid meta-scheduler based on an Ant Colony Optimization (ACO) algorithm is proposed, which is capable of co-allocating both optical networking and grid resources, under an integrated, extended and distributed control plane that supports advance reservations. The blocking probability and the delay for starting the processing of a request are evaluated for the proposed meta-scheduler under different resource co-allocation algorithms and different meta- and local scheduling policies, including the influence of the information aggregation across grid nodes. In addition, the benefits of the proposed approach are shown, such as grid and networking resource integration at the control plane, and capital expenditure reductions at the deployed optical network when compared to an immediate reservation scenario.

Practical, Real-time Centralized Control for CDN-based Live Video Delivery

Live video delivery is expected to reach a peak of 50 Tbps this year. This surging popularity is fundamentally changing the Internet video delivery landscape. CDNs must meet users' demands for fast join times, high bitrates, and low buffering ratios, while minimizing their own cost of delivery and responding to issues in real-time. Wide-area latency, loss, and failures, as well as varied workloads ("mega-events" to long-tail), make meeting these demands challenging. An analysis of video sessions concluded that a centralized controller could improve user experience, but CDN systems have shied away from such designs due to the difficulty of quickly handling failures, a requirement of both operators and users. We introduce VDN, a practical approach to a video delivery network that uses a centralized algorithm for live video optimization. VDN provides CDN operators with real-time, fine-grained control. It does this in spite of challenges resulting from the wide-area (e.g., state inconsistency, partitions, failures) by using a hybrid centralized+distributed control plane, increasing average bitrate by 1.7x and decreasing cost by 2x in different scenarios.