In the field of aerial photography, UAVs can be used as an ideal carrier of sensors. It is meaningful to plan its coverage path combined with the sensor model. Previous works mainly used decentralized coverage to realize UAV formation cooperative operation, but for the aerial photography scene of a single task, the decentralized coverage algorithm is not effective. In this paper, a centralized coverage algorithm of UAV formation for aerial photography is proposed, which is divided into two sub-problems: coverage path planning and formation control. In the coverage path planning, due to high repetition rate and excessive number of turns of the traditional PRM algorithm, the constraint of the number of turns is introduced, and the back-and-forth mode is used to improve it. In formation control, in order to more accurately evaluate the performance of the coverage path, it refers to the consensus theory and combines the artificial potential field method to guide the reverse-V UAV formation to follow the coverage path. Multi-group simulations show that the proposed algorithm is feasible to implement the concentrated coverage for aerial photography under the comprehensive consideration of path length, number of turns, calculation time, coverage rate and repeating rate.

Concentrated Coverage Path Planning Algorithm of UAV Formation for Aerial Photography

With the rapid growth of different massive applications and parallel flow requests in Data Center Networks (DCNs), today's providers are confronting challenges in flow forwarding decisions. Since Software Defined Networking (SDN) provides fine granular control, it can be intelligently programmed to distinguish between flow requirements. The present article proposes a knapsack model in which the link bandwidth and incoming flows are modeled as a knapsack capacity and items, respectively. Furthermore, each flow consists of two size and value aspects, acquired through flow size extraction and the type of service value assigned by the SDN controller decision. Indeed, the current work splits the incoming flow size range into Type of Service (ToS) decimal value numbers. The lower the flow size category, the higher the value dedicated to the flow. Particle Swarm Optimization (PSO) optimizes the knapsack problem and first forwards the selected flows by KP-PSO, and the non-selected-flows second. To address the shortcomings of these methods in the event of dense parallel flow detection, the present study puts the link under the threshold of a 70 percent load by simultaneous requests. Experimental results indicate that the proposed method outperforms Sonum, Hedera, and ECMP in terms of flow completion time, packet loss rate, and goodput regarding flow size requirements.

/pdf/flow-aware-forwarding-in-sdn-datacenters-using-a-knapsack-3som5xbmk0.pdf

Flow aware Forwarding in SDN Datacenters Using a Knapsack PSO Based Solution

With the rapid growth of different massive applications and parallel flow requests in Data Center Networks (DCNs), today’s providers are confronting challenges in flow forwarding decisions. Since Software Defined Networking (SDN) provides fine granular control, it can be intelligently programmed to distinguish between flow requirements. The present article proposes a knapsack model in which the link bandwidth and incoming flows are modeled as a knapsack capacity and items, respectively. Furthermore, each flow consists of two size and value aspects, acquired through flow size extraction and the type of service value assigned by the SDN controller decision. Indeed, the current work splits the incoming flow size range into Type of Service (ToS) decimal value numbers. The lower the flow size category, the higher the value dedicated to the flow. Particle Swarm Optimization (PSO) optimizes the knapsack problem and first forwards the selected-flows by KP-PSO, and the non-selected-flows second. To address the shortcomings of these methods in the event of dense parallel flow detection, the present study puts the link under the threshold of a 70% load by simultaneous requests. Experimental results indicate that the proposed method outperforms Sonum, Hedera, and ECMP in terms of flow completion time, packet loss rate, and goodput regarding flow size requirements.

/pdf/flow-aware-forwarding-in-sdn-datacenters-using-a-knapsack-36yc0zyjg9.pdf

Flow-Aware Forwarding in SDN Datacenters Using a Knapsack-PSO-Based Solution

Software-Defined Networking (SDN) emerges as one of the leading technologies to address the pressing networking problems such as network virtualization and data center complexity issues using programmable switches and controllers. To well exchange information and have coordinated control for the SDN environment, the multi-controller SDN network has been proposed. Unfortunately, this network architecture still faces the problem of faulty controllers that may forge the command arbitrarily, and then the whole network will be broken down easily. Thus, it is important to propose the fault-tolerance scheme under the SDN network system. In this paper, a new SDN environment called the Multi-Controller Overlay Groups (MCOG) where each device is managed by the controllers is proposed. Besides, the degree of the faulty influence will be revised to define the different bounds of fault tolerance in the MCOG environment. Furthermore, the new protocol named General Dynamic Multi-Controller Agreement (GDMCA) protocol is proposed to solve the Byzantine Agreement (BA) problem in the MCOG environment. Based on the proof of complexity, it can show that the proposed GDMCA protocol is optimal under the MCOG environment.

Improving the fault-tolerance of software-defined networks with dynamic overlay agreement

The issue of non-controller based data center network highlights the limitation of programmability, reconfiguration and network devices overhead which consists of both control and data plane coupling inside. This limitation causes difficulty in reconfiguration and resources management of network and devices overhead, leading to decreasing in throughput, bandwidth and losses in packet data traffic. This paper draws attention to the features of controller based Software Defined Network (SDN) network and its ability to enhance the network performance and management. Simulation using Gns3 is done for two comparison scenarios applied to simple tree data center topology: a) non-controllers based network using cisco router and switch, and b) controller based SDN network on Opeflow switch, Opendaylight controller and Openflow manager (OFM). Using Iperf tool, Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) traffics generation is applied and measured in both scenarios. The result of application has shown that the controller based SDN network provides high performance in throughput, bandwidth and low value of Jitter. In contrast, the non-controller based network provides low performance in throughput and bandwidth and high value of Jitter. In addition, simulation has shown the ability of controller based network in programming, softwarizing and Application Programmable Interfaces management resources.

Performance Evaluation of Controller Based SDN Network Over Non-controller Based Network in Data Center Network

The blooming of cloud computing leads to the rapid expansion of data center networks (DCN) Conventional link state routing algorithms like OSPF are widely adopted in data center networks, however, those routing algorithms bring great control overheads and long convergence time Recently, topology-aware routing methods are considered to be efficient especially in data center networks with regular topologies Lots of topology-aware routing methods (eg, Fat-Tree and BCube) have been proposed for specific data center network topologies This paper first proposes a formalized method to describe regular topologies and a regular Topology Description Language (TPDL) based on this method TPDL is well designed to accurately define regular network topologies in a clear way leveraging their regularities Based on the Software-Defined Networking (SDN) technology, this paper also proposes a novel topology-aware routing scheme: cRetor (controller-side REgular TOpology Routing scheme) Different from other topology-aware routing methods, cRetor is a TPDL-based general routing method, which means it is expected to work on different kinds of regular topologies In this scheme, TDPL files are used as a priori knowledge to build an initial topology in the SDN controllers, which eliminates the process of topology discovery via Link Layer Discovery Protocol (LLDP) and hence relieves the bandwidth and processing burdens on controllers Besides, we also apply the A-star algorithm to SDN controllers to speed up the routing selection, where TPDL's distance formulas act as the heuristic function The experimental results show that cRetor outperforms LLDP-based SDN, OSPF and DCell in routing calculation performance, convergence speed, routing overheads and fault tolerance

/pdf/cretor-an-sdn-based-routing-scheme-for-data-centers-with-cjepwkxu8x.pdf

Chengxin Liu

Papers

cRetor: An SDN-Based Routing Scheme for Data Centers With Regular Topologies