Hybrid SDN Research Articles

Joint Switch Upgrade and Controller Deployment in Hybrid Software-Defined Networks

To improve traffic management ability, Internet Service Providers (ISPs) are gradually upgrading legacy network devices to programmable devices that support Software-Defined Networking (SDN). The coexistence of legacy and SDN devices gives rise to a hybrid SDN. Existing hybrid SDNs do not consider the potential performance issues introduced by a centralized SDN controller: flow requests processed by a highly loaded controller may experience long tail processing delay; inappropriate multi-controller deployment could increase the propagation delay of flow requests. In this paper, we propose to jointly consider the deployment of SDN switches and their controllers for hybrid SDNs. We formulate the joint problem as an optimization problem that maximizes the number of flows that can be controlled and managed by the SDN and minimizes the propagation delay of flow requests between SDN controllers and switches under a given upgrade budget constraint. We show this problem is NP-hard. To efficiently solve the problem, we propose some techniques (e.g., strengthening the constraints and adding additional valid inequalities) to accelerate the global optimization solver for solving the problem for small networks and an efficient heuristic algorithm for solving it for large networks. The simulation results from real network topologies illustrate the effectiveness of the proposed techniques and show that our proposed heuristic algorithm uses a small number of controllers to manage a high amount of flows with good performance.

Routing Stability in Hybrid Software-Defined Networks

Software-defined networks (SDNs) facilitate more efficient routing of traffic flows using centralized network view. On the other hand, traditional distributed routing still enjoys the advantage of better scalability, robustness, and swift reaction to events such as failure. There are therefore significant potential benefits to adopt a hybrid operation where both distributed and centralized routing mechanisms co-exist. This hybrid operation however imposes a new challenge to network stability since a poor and inconsistent design can lead to repeated route switching when the two control mechanisms take turns to adjust the routes. In this paper, we discuss ways of solving the stability problem. We first define stability for hybrid SDNs and then establish a per-priority stabilizing framework to obtain stable routing patterns. For each priority class, we discuss three approaches to reach hybrid SDN stability: global optimization, greedy, and local search. It is argued that the proposed local search provides the best tradeoff among cost performance, computational complexity, and route disturbance. Furthermore, we design a system on a centralized controller, which utilizes those algorithms to stabilize the network. The design is implemented and extensively tested by simulations using realistic network information, including a trace of the Abilene network and data from a tier-1 Internet service providers backbone network.

SOTE: Traffic engineering in hybrid software defined networks

Traffic engineering (TE) is an efficient method to balance flows in a network. Existing TE solutions mainly focus on routing traffic along shortest paths between source and destination nodes, but ignore the likely network congestion. With the emergence of Software Defined Networking (SDN), through the deployment of SDN switches, we can enable flexible routing by splitting flows arbitrarily among multi-paths. However, due to technical, organizational and economical challenges of full SDN deployment, deploying SDN incrementally may be a more practical solution. Therefore, in this paper, we focus on a hybrid SDN architecture, where both legacy routers and SDN switches coexist. To explore routing optimization of TE in a hybrid SDN, we formulate a Mixed Integer Non-Linear programming (MINLP) problem and propose a heuristic algorithm SOTE to jointly optimize the OSPF weight setting and traffic splitting ratio of SDN nodes. Through extensive simulation and implementation on our prototyped testbed, we demonstrate that SOTE outperforms other algorithms in minimizing the maximum link utilization (MLU) of a network. Moreover, we also demonstrate that 10% deployment of SDN nodes can reap the most of benefit.

A Survey of Deployment Solutions and Optimization Strategies for Hybrid SDN Networks

A hybrid software defined networks (SDN) network contains both traditional and SDN network, which combines the robustness of traditional protocols with the flexibility of SDN while avoiding their limitations and incompatibility. However, a hybrid SDN network comes with its own set of challenges, including error-prone deployment processes, risks of inconsistency, and complex incremental deployment strategies. In this paper, we present a survey of the deployment solutions and optimization strategies for hybrid SDN networks. We systematically review solutions to control plane and data plane deployments, and describe typical use cases of hybrid SDN networks. We discuss and compare various optimization strategies from perspectives of traffic engineering, resource saving, network control capacity, and network security. This paper aims to provide insights to researchers into the future development of hybrid SDN networks and inspire more efforts in this area.

Match Field based Algorithm Selection Approach in Hybrid SDN and PCE Based Optical Networks

The evolving internet-based services demand high-speed data transmission in conjunction with scalability. The next generation optical network has to exploit artificial intelligence and cognitive techniques to cope with the emerging requirements. This work proposes a novel way to solve the dynamic provisioning problem in optical network. The provisioning in optical network involves the computation of routes and the reservation of wavelenghs (Routing and Wavelength assignment -RWA). This is an extensively studied multi-objective optimization problem and its complexity is known to be NP-Complete. As the exact algorithms incurs more running time, the heuristic based approaches have been widely preferred to solve this problem. Recently the software-defined networking has impacted the way the optical pipes are configured and monitored. This work proposes the dynamic selection of path computation algorithms in response to the changing service requirements and network scenarios. A software-defined controller mechanism with a novel packet matching feature was proposed to dynamically match the traffic demands with the appropriate algorithm. A software-defined controller with Path Computation Element-PCE was created in the ONOS tool. A simulation study was performed with the case study of dynamic path establishment in ONOS-Open Network Operating System based software defined controller environment. A java based NOX controller was configured with a parent path computation element. The child path computation elements were configured with different path computation algorithms under the control of the parent path computation element. The use case of dynamic bulk path creation was considered. The algorithm selection method is compared with the existing single algorithm based method and the results are analyzed.

Compressive Traffic Monitoring in Hybrid SDN

Hybrid software-defined network (SDN) is a network where legacy routers and SDN routers coexist during the incremental deployment of SDNs. The existing SDN router placement methods mainly focus on maximizing the traffic engineering performance under a limited budget. Traffic engineering requires real-time link-load information. However, the latency for collecting the global link-load information can be prohibitively long in a wide area network due to the long interior gateway protocol convergence time. Inspired by the sparsity of the link load, we propose a novel compressive traffic monitoring method for collecting real-time load information of all links. In this method, the controller only needs to collect the load of a small subset of important links and then estimates the link load of the rest. The minimal number of SDN routers is placed to cover these important links. We use real-world topologies and traffic matrices to evaluate our method. Experiment results show that our method can quickly estimate the global link load at an error rate of 5% within sub-seconds. Compared with the state-of-the-art methods, our method has better adaptability to the dynamic traffic changes and can reduce the maximal link usage by 39%.

A Routing Framework for Offloading Traffic From Cellular Networks to SDN-Based Multi-Hop Device-to-Device Networks

Device-to-device (D2D) communications are set to form an integral part of future 5G wireless networks. D2D communications have a number of benefits such as improving energy efficiency and spectrum utilization. Until now much of the D2D research in LTE and 5G-type network scenarios have focused on direct (one-hop) communications between two adjacent mobile devices. In this paper, we propose a new routing framework called virtual ad hoc routing protocol (VARP). This framework introduces significant advantages such as better security, lower routing overheads, and higher scalability, when compared to conventional ad hoc routing protocols. It also reduces traffic overhead in LTE networks using multi-hop D2D communications under management of a software defined networking (SDN)-controller. Further, it enables the development of various types of routing protocols for different networking scenarios. To this end, a source-routing based protocol was developed on top of VARP, referred to as VARP-S. We present a detailed analytical study of routing overhead in the VARP-S protocol, as compared to overhead analysis of our previous proposed hybrid SDN architecture for wireless distributed networks (HSAW) Our results show that VARP-S, compared to HSAW, achieves higher network scalability and lower power consumption for mobile nodes.

Hierarchical Wireless Vehicular Fog Architecture: A Case Study of Scheduling Electric Vehicle Energy Demands

Several novel and promising wireless vehicular-network applications have been developed recently. Examples include trip planning, media sharing, and Internet access. However, sufficient network resources [e.g., equipped vehicles, base stations (BSs), roadside units (RSUs), and other infrastructure] to support these applications are not yet available or are deployed at a slow pace. Moreover, these applications require considerable efforts in information gathering and data processing to allow quick decision making and fast feedback to all users. This imposes significant challenges on the development of an efficient wireless vehicularcommunication platform. In this article, we propose a new hierarchical software-defined-network (SDN)-based wireless vehicular fog architecture called a hierarchical SDN for vehicular fog (HSVF) architecture. The HSVF is based on a hybrid SDN control plane that reinforces centralized and distributed management. The proposed SDN control plane includes a trajectory prediction module to mitigate the drawbacks of the frequent handover problem between the RSUs and vehicles. The proposed architecture is then evaluated using a relevant case study that addresses the scheduling of electric vehicle (EV) energy demands.

ProgLIMI: Programmable LInk Metric Identification in Software-Defined Networks

In this paper, we propose the Programmable LInk Metric Identification (ProgLIMI) infrastructure for software-defined networking (SDN) networks. ProgLIMI identifies round-trip link metrics (RTLMs) from accumulated end-to-end metrics of selected measurement paths by leveraging the flexible routing control capability of SDN networks. ProgLIMI mainly solves three sub-problems: 1) monitor placement; 2) linearly independent measurement path construction; and 3) flow rule design. To reduce measurement cost, ProgLIMI tries to minimize the number of required monitors and flow rules. In this paper, we address the three sub-problems for both full and hybrid SDN networks. For full SDN networks, ProgLIMI can achieve full RTLM identification using only one monitor and two flow rules in each SDN switch. In contrast, the RTLM identification in hybrid SDN networks is more complicated due to the routing constraint of hybrid SDN networks. We first prove that the monitor placement problem in hybrid SDN networks is NP-hard. We then formulate the monitor placement and measurement path selection problem in hybrid SDN networks and propose a greedy heuristic algorithm to solve the problem efficiently. Our evaluations on both physical testbed and simulation platform reveal that ProgLIMI can accurately identify the RTLMs (delay and loss rate). Besides, ProgLIMI is also resource efficient, i.e., it only requires two flow rules in each SDN switch and a small number of monitors, and the extra probing traffic load incurred by ProgLIMI is also low.

Dynamic Routing Method over Hybrid SDN for Flying Ad Hoc Networks

Due to the high mobility and dynamic topology of the FANET network, maintaining communication links between UAVs is a challenging task. The topology of these networks is more dynamic than traditional mobile networks, which raises challenges for the routing protocol. The existing routing protocols for these networks partly fail to detect network topology changes. Few methods have recently been proposed to overcome this problem due to the rapid changes of network topology. We try to solve this problem by designing a new dynamic routing method for a group of UAVs using Hybrid SDN technology (SDN and a distributed routing protocol) with a highly dynamic topology. Comparison of the proposed method performance and two other algorithms is simulated. The simulation results show that the proposed method has better results than traditional algorithms in the package delivery ratio, average end to end delay, packet loss, throughput and normalized routing Load.

Consistent update of distance vector routing hybrid SDN networks

Hybrid SDN networks are a transition between traditional networks and SDN networks. They can offer traditional services while achieving some SDN advantages such as better manageability. However, updates to hybrid SDN networks lack effective techniques, especially for the case where distance vector routing is involved. In this paper, we impose segment routing on updates to hybrid SDN networks, and formalize the application of segment routing in hybrid SDN networks. By combining ordered scheduling and two-phase commit, we propose the LFCA algorithm. The algorithm attempts to stitch the final path using segment routing and to install the routing information into the packet header first. Nevertheless, for flows that are not segmentable, the algorithm constructs the dynamic topology set that can react to the remote effect of updates, and evaluates every update operation by backtracking until it finds the longest consistent update sequence. Last, a two-phase commit mechanism is leveraged to update the remaining nodes. Our experiments verify that this algorithm can significantly save on rule overhead and time costs in comparison with prior techniques.

Traffic Engineering and Manageability for Multicast Traffic in Hybrid SDN

Multicast communication can effectively reduce network resources consumption in contrast with unicast. With the advent of SDN, current researches on multicast traffic are mainly conducted in the SDN scenario, thus to mitigate the problems of IP multicast such as the unavoidable difficulty in traffic engineering and high security risk. However, migration to SDN cannot be achieved in one step, hybrid SDN emerges as a transitional networking form for ISP network. In hybrid SDN, for acquiring similar TE and security performance as in SDN multicast, we redirect every multicast traffic to an appropriate SDN node before reaching the destinations of the multicast group, thus to build up a core-based multicast tree substantially which is first introduced in CBT. Based on the core SDN node, it is possible to realize dynamic control over the routing paths to benefit traffic engineering (TE), while multicast traffic manageability can also be obtained, e.g., access control and middlebox-supported network services. On top of that, multiple core-based multicast trees are constructed for each multicast group by fully taking advantage of the routing flexibility of SDN nodes, in order to further enhance the TE performance. The multicast routing and splitting (MRS) algorithm is proposed whereby we jointly and efficiently determine an appropriate core SDN node for each group, as well as optimizing the traffic splitting fractions for the corresponding multiple core-based trees to minimize the maximum link utilization. We conduct simulations with different SDN deployment rate in real network topologies. The results indicate that, when 40% of the SDN switches are deployed in HSDN as well as calculating 2 trees for each group, HSDN multicast adopting MRS algorithm can obtain a comparable TE performance to SDN multicast.

A Hybrid Software Defined Networking Architecture for Next-Generation IoTs

A Hybrid Software Defined Networking Architecture for Next-Generation IoTs

Utility-Optimized Flow-Level Bandwidth Allocation in Hybrid SDNs

The software-defined network (SDN) is a new networking paradigm to improve network performance via logically centralized control and open standardized interfaces. However, the introduction of SDN technology faces many difficulties due to operational and economic constraints. Therefore, an incremental deployment scenario, the so-called hybrid SDN, is preferred. The transition from a legacy network to a pure SDN may take a long time; hence, it is of vital importance to consider the network optimization problem for hybrid SDNs. With SDN-enabled devices, multi-paths, where each flow can have multiple alternative paths, can be supported in bandwidth allocation. In contrast to traditional bandwidth allocation mechanisms in pure IP networks and full SDNs, this paper proposes a utility maximization model with the coexistence of single paths and multi-paths in the network, which aims to facilitate the transition to SDNs. We also design a novel algorithm to solve the maximization model, which is no longer strictly concave. Extensive simulations are conducted to evaluate the performance of the proposed bandwidth allocation strategy. Compared with existing strategies, our strategy has a good performance in terms of utility improvement. The results also show that with an increasing number of devices deployed in the SDN, more paths can be used to allocate the bandwidth; thus, a greater network utility can be achieved.

A centralized secure plan for detecting and mitigation incidents in hybrid SDN

The information technology sector has experienced phenomenal growth during recent years. To follow this development many new technologies have emerged to satisfy the expectations of businesses and customers, such as Cloud Computing, mobility, virtualization, Internet of things and big data. Traditional network cannot longer support this growth and suffers more and more in terms of misconfiguration,management and configurations complexity. Software defined network (SDN) architectures can be considered as a big revolution in the field of computer networks, because they offer a centralized control on infrastructure, services and the applications deployed which facilitate configuration and management on the network. The implementation of this type of architecture is not obvious and requires great expertise and good handling and management of network equipment. To remedy this problem the SDN architectures have evolved towards distributed and hybrid architectures. Despites the advantages of using SDN, security issues remain a real obstacle in front of the deployment of this type of architecture. The centralized architecture of this type of networks makes it vulnerable to several types of attacks and intrusions, and the implementation of security equipment generally causes a decrease in performance and increase latency.

Dynamic Routing Method over Hybrid SDN for Flying Ad Hoc Networks

Due to the high mobility and dynamic topology of the FANET network, maintaining communication links between UAVs is a challenging task. The topology of these networks is more dynamic than traditional mobile networks, which raises challenges for the routing protocol. The existing routing protocols for these networks partly fail to detect network topology changes. Few methods have recently been proposed to overcome this problem due to the rapid changes of network topology. We try to solve this problem by designing a new dynamic routing method for a group of UAVs using Hybrid SDN technology (SDN and a distributed routing protocol) with a highly dynamic topology. Comparison of the proposed method performance and two other algorithms is simulated. The simulation results show that the proposed method has better results than traditional algorithms in the package delivery ratio, average end to end delay, packet loss, throughput and normalized routing Load.

Hybrid SDN Networks: A Survey of Existing Approaches

Software defined networking (SDN) decouples the control plane from the data plane of forwarding devices. This separation provides several benefits, including the simplification of network management and control. However, due to a variety of reasons, such as budget constraints and fear of downtime, many organizations are reluctant to fully deploy SDN. Partially deploying SDN through the placement of a limited number of SDN devices among legacy (traditional) network devices, forms a so-called hybrid SDN network. While hybrid SDN networks provide many of the benefits of SDN and have a wide range of applications, they also pose several challenges. These challenges have recently been addressed in a growing body of literature on hybrid SDN network structures and protocols. This paper presents a comprehensive up-to-date survey of the research and development in the field of hybrid SDN networks. We have organized the survey into five main categories, namely hybrid SDN network deployment strategies, controllers for hybrid SDN networks, protocols for hybrid SDN network management, traffic engineering mechanisms for hybrid SDN networks, as well as testing, verification, and security mechanisms for hybrid SDN networks. We thoroughly survey the existing hybrid SDN network studies according to this taxonomy and identify gaps and limitations in the existing body of research. Based on the outcomes of the existing research studies as well as the identified gaps and limitations, we derive guidelines for future research on hybrid SDN networks.

Intelligent path control for energy-saving in hybrid SDN networks

As power consumption of the internet has been growing quickly in recent years, saving energy has become an important problem of networking research. Software-Defined Networking (SDN) brings excellent opportunities to improve network performance and reduce energy consumption by flexible centralized control. However, due to budget constraints and technique limitations, ISPs can upgrade only a limited number of conventional switches in backbone networks to SDN devices at one time. In this paper, we propose one heuristic scheme for incrementally deploy SDN switches in hybrid SDNs, the objective of which is to achieve energy saving by rerouting the flows to shut down idle links and switches as many as possible. Our solution can achieve two objectives: 1) maximizing the network control ability with a given SDN switches upgrading budget constraint, and 2) maximizing energy saving by shutting down idle links and switches with deployed SDN switches. The results of evaluations show that our scheme can achieve 95% of the number of flows controlled with only 10% of upgrading cost, and it also can achieve saving more about 10% of the total power consumption when compared to the existing solutions.

Efficient topology discovery algorithm for software‐defined networks

Software-defined networking (SDN) already has an established presence in the networking industry as an emerging paradigm for designing network architectures, decoupling the control from the forwarding plane and offering a centralised way of network management. Cloud and enterprise infrastructure engineers have already adopted such techniques for building up their environments, deliberating the cost and flexibility advantages gained from this technology. However, smaller companies may choose a progressive replacement of their equipment due to operational and budget constraints. Hence, mixing equipment could lead up to hybrid SDN environments making network management even more complex. In this study, an event-based generic topology discovery algorithm, capable of providing an efficient packet discovery mechanism using existing protocols in SDN networks, is proposed. For testing and evaluation purposes, address resolution protocol and link layer discovery protocol are being used to extract the information needed and reconstruct the topology to the controller. Implementation is accomplished using Internet Engineering Task Force's ForCES framework.

Traffic engineering in hybrid SDN networks with multiple traffic matrices

Traffic engineering (TE) is an efficient tool for optimizing traffic routing and balancing the flows in networks. Traffic is dynamic, previous TE optimization over a single traffic matrix (TM) have some limitations, because a single TM can have big measurement errors and is insufficient to depict the traffic flucuations. Thus, we consider using multiple TMs to overcome these limitations. With the emergence of Software Defined Networking (SDN), we can route flows more flexibly and better balance the flows over multiple TMs. However, due to the difficulties of full SDN deployment, hybrid SDN networks will be the prevailing architectures in the near future. Therefore, optimizing the routing over multiple TMs in a hybrid SDN network is of great interest.In this paper, we first formulate the problem of TE over multiple TMs and prove its NP-hardness. Next, we propose a heuristic algorithm for optimizing routing over multiple TMs by combining offline weight setting optimization with online splitting ratio optimization. Furthermore, we prove that the routes obtained in our algorithm are loop-free, and we provide an upper and lower bound of our proposed algorithm. Finally, we evaluate our method on measured traffic datasets with three network topologies. The results of extensive experiments demonstrate that the maximum link utilization of a network can be optimized better using our proposed algorithm.