Software Defined Satellite Networks Research Articles

Optimized Controller Provisioning in Software-Defined LEO Satellite Networks

The controller provisioning, which adjusts the number, locations, and members of satellite controllers adaptive to the dynamic network load and topology, fundamentally impacts the performance of software-defined satellite networks (SDSNs). An ideal provisioning strategy should achieve a low total control overhead throughout the entire satellite operation period, which is extremely challenging since the network load can only be predicted in a short time scale. Existing methods can hardly achieve this goal for they greedily configure controllers in each time slot, where switches have to frequently migrate from one controller to another. In this paper, we focus on achieving globally optimized strategies with only current network load information. We firstly propose a comprehensive control overhead model and formulate the Controller Provisioning Problem (CPP) in SDSNs as a non-convex integer programming problem. To solve the problem, we propose an approximate algorithm named AROA by introducing a regularization framework and based on randomized rounding. We theoretically derive its competitive ratio. To produce strategies in time for future large satellite constellations, we further propose a more efficient heuristic algorithm HROA. Evaluations on our built simulation system show that our proposed methods significantly outperform related schemes in control overhead, latency, and scalability.

DR-SDSN: An Elastic Differentiated Routing Framework for Software-Defined Satellite Networks

Software-defined satellite networking (SDSN) has recently gained unprecedented attention due to its great controllability for traffic delivery. However, it is still facing several fundamental challenges in routing, which mainly involves effective network maintenance, heterogeneous network convergence, and customized flow steering. Hence, in this article, we propose an elastic routing framework for SDSN, aiming to first build a robust control path for signalling exchanges, then offer a transparent channel for IP services based on Loc/ID mappings and associated encapsulations, and finally enable hybrid packet forwarding manners to meet user various demands. Moreover, we define a new 8 B network header for DR-SDSN to further decrease overheads in packet encapsulations, where 16-bit addresses are used instead of 32-bit IPv4 and 128-bit IPv6 addresses. At last, we have implemented a corresponding proof-of-concept prototype with the modified Ryu and OvS, and the Linux socket application programming interface is also extended to handle our protocol with 16-bit addresses. Extensive evaluations are performed and associated results have confirmed the feasibility and advantages of the proposed DR-SDSN framework.

A Service Function Chain Deployment Scheme of the Software Defined Satellite Network

The aim of this study was to reduce the influence of highly dynamic substrate network topology and large transmission delay caused by long communication distance between satellites and ground in Software Defined Satellite Networks (SDSNs), and a Partial Observation Markov Decision Process (POMDP)-based service function chain (SFC) deployment scheme of SDSN is proposed. Under this SDSN architecture, the network topology changes could be obtained through the SDN centralized control ability. Due to the topology changes, which may cause inevitable observation errors and transmission delays, the complete actual topology and network states cannot be obtained in real time. Thus, we put forward a POMDP model–based SFC deployment scheme, and an approximate iterative algorithm to solve the problem, aiming at optimizing the end-to-end network delay in the SDSN. The simulation results show that our model can optimize the delay of SFC deployment process, and improve the resource utilization and network throughput of the SDSN.

Experimental Evaluation of Algorithms for Packet Routing in Software Defined Network

The packet routing problem in a software defined network is formulated and a greedy algorithm is proposed. An alternative approach to approximately solve this problem by means of reduction to a special case of the fractional length-bounded maximum multicommodity flow is suggested. Experimental comparison of the greedy algorithm and a fully polynomial-time approximation scheme (FPTAS) for fractional length-bounded maximum multicommodity flow is carried out on the testing instances representing prospective software defined satellite network.

Multi-Objective Optimisation in Multi-QoS Routing Strategy for Software-Defined Satellite Network.

The satellite network plays an increasingly important role in the global communication. With the development of communication technology, quality of service requirements have become more and more complex and diverse and the quality of service routing strategy of software-defined satellite network has become a more and more hot and difficult issue. In this paper, an interval-type-2 fuzzy set routing algorithm is proposed. Firstly, the multi- quality of service routing problem in software-defined satellite network is modeled. Then, the interval-type-2 fuzzy set routing algorithm is proposed to make fuzzy decisions. A series of experiments conducted in Network Simulator (Version 2.35) have proved that the proposed interval type-2 fuzzy set routing algorithm can reduce average delay, increase total throughput and reduce packet drop rate.

Reliability analysis of software-defined satellite network based on control delay

At present, there are few studies about the link failure and reliability of software defined satellite network (SDSN). However, the inter-satellite links (ISLs) may break down because of the long distance between the satellites, the high relative moving speed and the easy interference of the wireless channel. At the same time, most researches on controller deployment in SDSN only consider the transmission delay but ignore the processing delay. To solve these problems, considering the failure probability of intersatellite link, the failure probability model of ISLs is designed, the queuing delay and processing delay are added into the delay model, and the software defined satellite network reliability analysis model based on control delay is established. This model can describe the reliability of the network against link failure. The simulation results show that the model is consistent with the actual situation and can provide some reference value for controller deployment in SDSN.

A topology-based optimization method for software-defined satellite network control

Satellite network is gaining significant attention, and software-defined networking architecture is more and more popular as applied in many traditional networking fields. In order to meet the diversified user service requirements and the continuously expanding application scenario requirements, the research of software defined satellite network combining satellite network and software definition has gradually become a research hotspot. Aiming at the problem of how to optimize the control function of software-defined satellite network, this paper proposes a control optimization method based on topological structure. By quantifying the controllability of the network structure and eliminating the special characteristic structure, the controllability of the network is improved, and then the control function of software-defined satellite network is optimized. The simulation results show that the controllability of the network is improved by the method.

Elastic Resilience for Software-Defined Satellite Networking: Challenges, Solutions, and Open Issues

Satellite networks have long been regarded as a key enabler for ubiquitous Internet access and global data distribution. However, since they are highly dynamic and much more vulnerable to various failures, how to detour traffic around fault satellites and interrupted links becomes an important but challenging issue. Thanks to the emerging software-defined networking, great controllability can be introduced to the satellite networks for agile management and automation. Hence, in this article, we focus on elastic resilience for software-defined satellite networking, and propose a preliminary solution to cope with the related fundamental challenges in guarantees of controller reachability, collections of network status, and failure detection and recovery. We also discuss several key open issues to be urgently addressed, hoping to shed some light on this promising land.

Multi-QoS adaptive routing algorithm based on SDN for satellite network

With the development of communication services, satellite network services have developed from the traditional single type of services to multiple types of services. Different types of services need to meet different Quality of Service (QoS) requirements. The traditional satellite network algorithm does not distinguish the services, so the high QoS service in the network cannot get timely service. However, the architecture of Software Defined Satellite Networking (SDSN) can solve this problem well. The controller in the SDSN has a global view and can obtain the node and link information of LEO satellites. Therefore, the SDSN can more effectively meet the demand of data service for QoS. In this paper, a satellite network architecture based on Software Defined Networking (SDN) is firstly established. Then an adaptive routing algorithm that can meet various QoS requirements is proposed. The final simulation results show that compared with SDRA algorithm and Dijkstra algorithm, this optimization algorithm has better performance in QoS satisfaction rate and bandwidth utilization.

An Energy-Efficient Topology Design and DDoS Attacks Mitigation for Green Software-Defined Satellite Network

As the continuous in-depth research of sixth generation (6G) technology, the satellite networks in the Space-Air-Ground Integrated Network (SAGIN) have received more and more attention. However, since satellite nodes have the characteristics of limited resources and dynamic link switching, it is important to effectively save energy in satellite networks. In this paper, we focus on how to make Software-Defined Satellite Networks (SDSN) more energy efficient. First, we propose an energy consumption model for satellite networks. Based on this model, we put forward an improved network topology generation algorithm, which can comprehensively consider the link switching energy consumption and the inter-satellite link energy consumption. Then, considering the huge energy consumption caused by abnormal traffic in the satellite network, we propose a DDoS mitigation mechanism in the satellite network, aiming to reduce the extra energy consumption generated by processing abnormal traffic in the satellite node. Finally, through performance evaluation, the proposed network topology generation algorithm and DDoS attack mitigation strategy can effectively reduce network energy consumption.

Intelligent Quality of Service Routing in Software-Defined Satellite Networking

Software-Defined Satellite Networking (SDSN) has emerged as a new paradigm that offers the programmability required to dynamically manage a satellite network. However, the characteristics of SDSN bring several important issues to be solved in the routing scheme. First, interface protocols of the controller incur nonnegligible overhead, which affects the general traffic. Second, more than one controller is required to ensure the reliability of SDSN, which means that they should cooperate with each other to realize the routing function. Third, how to make full use of the advantage of SDSN's centralized management for routing algorithm is worth studying. In this paper, we first propose an SDSN architecture to realize flexible centralized management. Based on this architecture, Intelligent Quality of Service (QoS) Routing scheme is proposed and evaluated. Intelligent QoS Routing (IQR) scheme is composed of overhead balancing strategy, controller cooperation strategy, and IQR algorithm. Overhead balancing strategy effectively reduces the impact of overhead on general traffic, which improves the performance of IQR algorithm. Controller cooperation strategy adopts the ensemble Support Vector Regression (SVR) from artificial intelligence tools to enhance the consistency of different controllers' network views under low frequency situation, which will provide a more accurate reference for IQR algorithm and other management strategies. IQR algorithm takes full advantage of SDSN's centralized control and rich data to offer fine-grained QoS guarantee intelligently. Simulation results show that IQR scheme achieves better overhead balancing performance, more effective controller cooperation, and better QoS guarantee compared with the existing methods.

A Satellite Handover Strategy Based on the Potential Game in LEO Satellite Networks

In a low earth orbit (LEO) satellite network, handover management across satellite spot beams needs to be addressed to decrease handover times while using network resources efficiently since the speed of LEO satellites is much higher than that of mobile nodes. In this paper, we propose a novel satellite handover strategy based on the potential game for mobile terminals in a LEO satellite communication network. To continue communication with the counterpart, the user has to switch among the covered LEO satellites. In a software-defined satellite network (SDSN) architecture, the satellite handover can be viewed as a bipartite graph. To balance the satellite network workload, we propose a terminal random-access algorithm based on the target of userspace maximization. The simulated handover conducted on a typical LEO satellite network, Iridium, corroborates the effectiveness of the proposed handover strategy.

On three approaches to length-bounded maximum multicommodity flow with unit edge-lengths

The paper presents a comparison between three approaches to solving the length-bounded maximum multicommodity flow problem with unit edge-lengths. Following the first approach, Garg and K?nemann?s, we developed an improved fully polynomial time approximation scheme for this problem. As the second alternative, we considered the well-known greedy approach. The third approach is the one that yields exact solutions by means of a standard LP solver applied to an LP model on the time-expanded network. Computational experiments are carried out on benchmark graphs and the graphs that model software defined satellite networks, to compare the proposed algorithms with an exact linear programming solver. The results of the experiments demonstrate a trade-off between the computing time and the precision of algorithms under consideration.

Cross Layer Optimization of Wireless Control Links in the Software-Defined LEO Satellite Network

The low earth orbit (LEO) satellite network can benefit from software-defined networking (SDN) by lightening forwarding devices and improving service diversity. In order to apply SDN into the network, however, reliable SDN control links should be associated from satellite gateways to satellites, with the wireless and mobile properties of the network taken into account. Since these characteristics affect both control link association and gateway power allocation, we define a new cross layer SDN control link problem. To the best of our knowledge, this is the first attempt to explore the cross layer control link problem for the software-defined satellite network. A logically centralized SDN control framework constrained by maximum total power is introduced to enhance gateway power efficiency for control link setup. Based on the power control analysis of the problem, a power-efficient control link algorithm is developed, which establishes low latency control links with reduced power consumption. Along with the sensitivity analysis of the proposed control link algorithm, numerical results demonstrate low latency and high reliability of control links established by the algorithm, ultimately suggesting the feasibility, both technical and economical, of the software-defined LEO satellite network.

A routing strategy for software defined satellite networks considering control traffic

A routing strategy for software defined satellite networks considering control traffic

Data evacuation from data centers in disaster-affected regions through software-defined satellite networks

Large-scale disasters can severely disrupt Information Technology (IT) infrastructure, e.g., Data Centers. Earthquakes, hurricanes, tsunamis, and other natural catastrophes may lead to such a scenario. Man-made threats, e.g., a High-Altitude Electromagnetic Pulse (HEMP), can also provoke such an aftermath. In the HEMP case, however, the aftermath might include damage even to non-terrestrial IT infrastructure, such as satellites. After any disaster, it is important that critical data located in the affected region be evacuated to secure locations where it can be useful for emergency operations, mission-critical activities, rescue and relief efforts, and society and businesses in general. To minimize the time it takes to perform this evacuation, we must use all available resources as efficiently as possible. This includes using the remaining satellites to connect the affected regions of the network to the unaffected ones. Utilizing the Software-Defined Network (SDN) paradigm applied to satellite networks, we propose an algorithm that can be executed by the SDN controller. This algorithm generates an evacuation plan for data located in possibly-isolated terrestrial systems, such as Data Centers, through the satellite network, towards final destinations in the main network. The evacuation plan is a transmission schedule that maximizes the amount of evacuated data. Considering the current industrial interest in mega satellite constellations, we compare how two constellations of 66 and 720 satellites perform in terms of amount of data evacuated. Our results show how the evacuation is affected by different satellite constellation configurations (i.e., buffers, inter-satellite link capacities, etc.). Since our approach allows for Traffic Engineering (TE) to be performed, we also demonstrate how it enables fair resource utilization among different affected infrastructures during data evacuation. Our illustrative examples also compare our method to an approach designed for Delay-Tolerant-Vehicle networks and show how our solution can evacuate up to 60% more data after a disaster.

Dynamic and static controller placement in Software-Defined Satellite Networking

Software-Defined Satellite Networking (SDSN) [1], similar to Software-Defined Networking (SDN) [2], has emerged as a new paradigm that offers the programmability required to dynamically configure and control a satellite network. As SDSN is large-scale network, recent proposals have advocated deploying multiple controllers that work cooperatively to enhance performance and scalability [3,4]. Nonetheless, this approach introduces a new problem: how many controllers are needed, and where should they be deployed? We call this controller placement problem, which can be divided into dynamic and static types. The former assumes that the network operator has already placed plenty of back-up controllers throughout the network. By changing the on-off status of them, it realizes adapting the number and location of active controllers with changing network conditions. On the contrary, the latter decides the controller deployment only for once before building SDSN. Related work only focuses on ground network and several important factors affecting the controller placement are not taken into account comprehensively. In this paper, we propose the framework and mechanism of SDSN, define the Dynamic Controller Placement Problem (DCPP) as well as Static Controller Placement Problem (SCPP), and introduce a heuristic method to solve them. Simulation results show that our solution improves the performance of SDSN.

Service function chain in small satellite-based software defined satellite networks

Software Defined Satellite Networks (SDSN) are proposed to solve the problems in traditional satellite networks, such as time-consuming configuration and inflexible traffic scheduling. The emerging application of small satellite and research of SDSN make it possible for satellite networks to provide flexible network services. Service Function Chain (SFC) can satisfy this need. In this paper, we are motivated to investigate applying SFC in the small satellite-based SDSN for service delivery. We introduce the structure of the multi-layer constellation-based SDSN. Then, we describe two deployment patterns of SFC in SDSN, the Multi-Domain (MD) pattern and the Satellite Formation (SF) pattern. We propose two algorithms, SFP-MD, and SFP-SF, to calculate the Service Function Path (SFP). We implement the algorithms and conduct contrast experiments in our prototype. Finally, we summarize the applicable conditions of two deployment patterns according to the experimental results in terms of hops, delay, and packet loss rate.

Fast lightweight reconfiguration of virtual constellation for obtaining of earth observation big data

Earth observation (EO) big data is playing the increasingly important role in spatial sciences. To obtain adequate EO data, virtual constellation is proposed to overcome the limitation of traditional EO facilities, by combining the existing space and ground segment capabilities. However, the current configuration pattern of virtual constellation is tightly coupled with the specific application requirements. This leads to the costly reconfigurations. Although the pattern of software defined satellite network can decouple topology reconfigurations from application requirements, it cannot be directly applied to the reconfigurations of virtual constellations because of some drawbacks. To address the problem, we propose a model of LEO-ground links control-covering (LGLC) to implement fast and lightweight reconfiguration for virtual constellation. LGLC uses a bipartite graph model to formalize the dispatch problem of the control information of virtual constellation reconfiguration, and the optimum solution can be got by the classical algorithm in polynomial time. According to the strategy obtained, only if a few satellites and stations receive the control information, virtual constellation can be reconfigured quickly. We also establish some metrics to evaluate the effect of LGLC. Extensive experiments are conducted to confirm the above claims.

SAT-FLOW: Multi-Strategy Flow Table Management for Software Defined Satellite Networks

Software-defined satellite network (SDSN) is a novel framework, which brings softwaredefined network technologies in the satellite networks. It has great potential to achieve effective and flexible management in the satellite networks. There are two burning issues to be solved for the flow table management in SDSN. First, the ternary content addressable memory (TCAM) space is limited on satellites and the flow table size should be reduced. Second, the frequent handovers will lead to an increase in the flow table size in SDSN. Due to the limited flow table space, a lot of flows will be dropped if the flow table is full during the handover. To address these issues, we first give a description of our focused flow table management problems. Then, we propose SAT-FLOW, a multi-strategy flow table management method for SDSN. SAT-FLOW considers three key points, limited TCAM space, classified traffic, and handover. SAT-FLOW contains two heuristic algorithms, named dynamic classified timeout (DCT) algorithm and timeout strategybased mobility management (TSMM) algorithm. DCT aims to reduce the flow table size and TSMM aims to reduce the drop flows during the handover. We implement SAT-FLOW and conduct contrast experiments. The experimental results verify the good performance in terms of transmission quality, idle_timeout values distribution, a 15.27%-24.34% decrease in flow table size, an 8.2%-10.4% decrease in drop-flow rate, and a 4.92%-5.7% decrease in table misses for the high priority traffic during the handover.