Link Overload Research Articles

Impact of Communication Link Overload on Power Flow and Data Transmission in Cyber–Physical Power Systems

Impact of Communication Link Overload on Power Flow and Data Transmission in Cyber–Physical Power Systems

Режими роботи маніпулятора ремонтно-евакуаційної машини

With modern methods of conducting military operations, the system of technical support of the troops is of great importance. One of the ways to increase the effectiveness of the system of technical support of troops is the use of armored repair and evacuation vehicles. It is possible to increase the technical capabilities of armored repair and evacuation vehicles by modernizing existing models, or creating qualitatively new vehicles that take into account the specifics of use and characteristic combat damage of modern weapons and military equipment, the type of engine of the military vehicle, its weight and dimensions and other characteristics. Improvement and modernization of armored repair and evacuation vehicles allows to ensure their effectiveness. Armored repair and evacuation vehicles demonstrate high efficiency when carrying out operations to extract or lift damaged or stuck, blocked, bogged down, sunken military equipment. In these cases, the traction force of the armored recovery vehicle's own engine is used or its own specialized means of evacuation: crane winches, polyspatch systems, crane booms together with power hydraulic cylinders of their drive, levers, other evacuation equipment. Features of the lifting and loading equipment include such modes of operation as lifting loads from a solid surface, detaching the load from a viscous surface, dragging at different angles to the support surface, and getting stuck. The most difficult in terms of dynamic overloads of all elements of the hydraulic manipulator is the mode of partial immersion and dense sticking of the load in clay soil, when after separation from it, the load under the action of the forces of elastic deformations of the suspension flies up to the height of a significant relaxation of the suspension and reaching the upper point, where its speed is zero, falls down on an elastic suspension. At the same time, a three-fold overload of the manipulator links is observed.

Simulation Study of Network Reconfiguration and Load-balancing Method for the Xinjiang Astronomical Observatory Data Center

The Xinjiang Astronomical Observatory Data Center faces issues related to delay-affected services. As a result, these services cannot be implemented in a timely manner due to the overloading of transmission links. In this paper, the software-defined network technology is applied to the Xinjiang Astronomical Observatory Data Center Network (XAO-DCN). Specifically, a novel reconfiguration method is proposed to realise the software-defined Xinjiang Astronomical Observatory Data Center Network (SDXAO-DCN), and a network model is constructed. To overcome the congestion problem, a traffic load-balancing algorithm is designed for fast transmission of the service traffic by combining three factors: network structure, congestion level and transmission service. The proposed algorithm is compared with current commonly load-balancing algorithms which are used in data center to verify its efficiency. Simulation experiments show that the algorithm improved transmission performance and transmission quality for the SDXAO-DCN.

OPLA-Tool-ASP: a Tool to Prevent Architectural Smells in Search-based Product Line Architecture Design

Search-based algorithms have been successfully employed in Product Line Architecture (PLA) design in the seminal approach named Multi-Objective Approach for Product-Line Architecture Design (MOA4PLA). This approach generates a set of alternative PLA designs, which optimize different architectural properties. In addition to these properties, the alternative PLA designs should have as few architectural smells as possible. Architectural smells can negatively impact PLA variability, PLA extensibility, SPL maintainability, and other non-functional attributes. However, one of the main findings of a previous study is that the tool that automates the application of MOA4PLA adversely introduces architectural smells in the automatically generated solutions. In this work, we present OPLA-Tool-ASP, which is a tool that implements guidelines to detect and prevent the architectural smells Unused Interface, Unused Brick, Concern Overload, and Link Overload in the context of MOA4PLA. An empirical study was carried out to assess the effectiveness of OPLA-Tool-ASP in preventing the aforementioned smells in the resulting PLA designs. The obtained results pointed out that the proposed tool is effective in both preventing the smells and improving the architectural properties selected for optimization.

FLOW-BASED ROUTING MODEL WITH LOAD BALANCING UNDER NETWORK SECURITY PARAMETERS

Background. In modern telecommunication networks, the functioning of network protocols is aimed at achieving a high level of Quality of Service and network security. Therefore, an urgent scientific and applied problem is the adaptation of routing solutions with load balancing to the requirements of network security. The novelty of the proposed model is the modification of the load balancing conditions, in which, in addition to the link bandwidth (Quality of Service indicator), the probability of its compromise (network security indicator) is also taken into account. The routing solutions obtained within the framework of the proposed model are aimed at reducing the overload of network links that have a high probability of compromise by switching traffic to more secure links.Objective. Developing the flow-based routing model with load balancing, which takes into account the parameters of network security.Methods. Analysis of all known publications on load balancing and network security. Synthesis of a load balancing flowbased routing model. Study of the influence of network security parameters of communication links on routing and load balancing processes.Results. A new condition for load balancing is proposed, which is a modification of the existing Traffic Engineering solution based on accounting the network security parameters - the probabilities of compromising communication links.Conclusions. In routing with load balancing, parameters of network security should be considered. Depending on the network state and user requirements, different models of network security parameters for load balancing processes can be used.

Flow-based information security risk-aware routing model using base score metrics of criticality vulnerabilities

The paper proposes an improved flow-based routing model taking into account information security risks using basic vulnerability criticality metrics. The model is based on the conditions for the implementation of single- and multipath routing, flow conservation, and prevention of overload of communication links of the telecommunications network (TCN). Within the proposed model, the problem of secure routing is formulated in an optimization form. The novelty of the developed model is that expressions are used to calculate routing metrics, which characterize the risk of information security in communication links of the TCN and in accordance with the NIST recommendations, take into account damages from the violation of confidentiality and integrity of information, availability of network resources in case of use of existing vulnerabilities; indicators of the complexity of exploiting vulnerabilities at network nodes and gaining access to network elements and the network as a whole due to the use of these vulnerabilities. As shown by the results of the study, the use of the proposed model of secure routing allows ensuring the calculation and use of routes with minimal risk of information security, thereby ensuring the maximum level of network security for packets transmitted in the TCN. The proposed approach to the formation of routing metrics can also be used to ensure comprehensive consideration in the process of solving routing problems of both network security indicators and quality of service indicators. The prospects for the development of the obtained solutions include the synthesis of models and methods of secure routing by which it would be possible to provide (guarantee) a given level of network security based on the calculation and use of appropriate routes in TCN.

Flow-based Routing Model with Load Balancing on the Traffic Engineering Principles Taking into Account the Information Security Risks

A practical approach to load balancing in a telecommunication network (TCN) is implementing Traffic Engineering (TE) technology principles to reduce link utilization and improve QoS level. In order to adapt TE solutions with network security requirements, this paper proposes a mathematical model for secure routing, which belongs to the class of flow-based optimization solutions. The model is based on the conditions of multi-flow routing implementation, flow conservation, and TCN link overload prevention. Due to this, the problem of secure routing is formulated in an optimization form. The model’s novelty is the modified conditions of load balancing in TCN. Along with the indicators of link capacity with the help of weighting coefficients, the network security (NS) indicators of TCN elements are also taken into account. The network security (NS) indicators in the TCN modeling process include information security risks of routers and communication links, losses from breach of confidentiality and integrity of information, probability of existing vulnerabilities exploitation, etc. The study confirmed the effectiveness of the proposed solution. On the test TCN topology, it is demonstrated that the use of a secure routing model allows to calculate the routes and provide such an order of load balancing, which compromises meeting the requirements of both QoS and NS. In the routing process, information security risk reduction in packet transmission by about 11.3% was accompanied by an increase (on average by 26%) in the upper bound of the network link utilization

DART: Data Plane Load Reduction for Traffic Flow Migration in SDN

In this paper, we present a traffic-aware flow migration approach, which reduces data plane load in Software-Defined Networking (SDN) during a network update. SDN update involves rerouting of multiple traffic flows to accommodate new flows. An unplanned flow migration schedule overloads the data plane by burdening the data links and flooding the rule-space of capacity-constrained SDN switches. The overload of data links and switches blocks the update process, and the network fails to address the Quality of Service (QoS) demands of the traffic flows, especially latency-sensitive flows. Prior approaches migrate flows without considering load reduction of the data plane along with QoS demands of the flows. In this work, we propose a load reduction strategy that prioritizes traffic flows based on QoS demands and aims to avoid link congestion and rule-space overflow during flow migration. The proposed scheme significantly reduces the maximum data link bandwidth usage. In particular, the maximum data link bandwidth usage is 13.22% less than the two-phase update approach.

Enhancement of the adaptive routing tensor model in the infocommunication network with providing quality of experience by the R-factor

The object of research is the routing processes and ensuring the quality of experience in the infocommunication network. To conduct research an improvement of the adaptive routing tensor model in an infocommunication network with quality of experience by the R-factor is proposed. The basis was a floe-based routing model that took into account possible packet losses caused by congestion of network elements and was represented by the conditions for implementing a multipath routing strategy, conditions of the flow conservation and conditions for preventing overload of communication links. To obtain in an analytical form the conditions for ensuring the quality of experience in terms of the R-factor, a tensor description of the infocommunication network is carried out. This allowed obtaining of analytical expressions for calculating the average end-to-end delay and the probability of packet loss, which were used to formulate the QoE conditions in terms of the R-factor.In the framework of the proposed model, solving the technological problem of adaptive routing solutions are reduced to solving the optimization problem of nonlinear programming for calculating route variables. The introduced optimality criterion allowed it possible to ensure the adaptive nature of route decisions, when an increase in QoE requirements led to an increase in the amount of network resource used. To solve the problem, methods of mathematical programming were used, which are implemented in the MatLab package.A study on a fragment of the infocommunication network made it possible to evaluate the adequacy and effectiveness of the proposed model. Using the obtained research results, it was possible to ensure the fulfillment of the specified QoE requirements in terms of the R-factor for the services provided to end users. Using the proposed model is characterized by high efficiency on load balancing across multiple routes in the infocommunication network. This was evidenced by the fact that at a given value of the R-factor, with an increase in the intensity of traffic entering the infocommunication network, there was a gradual increase in the number of routes involved. In other words, the network resource was distributed evenly and efficiently by 7–10 % relative to known analogues, which, when solving the same problem, immediately use all possible routes.

Modeling and analysis of cascading node-link failures in multi-sink wireless sensor networks

Due to the prominent advantages in network lifetime and energy balance, the application of multi-sink wireless sensor networks (WSNs) is becoming more and more widespread. However, their cascading robustness is still rarely studied. Therefore, in this paper, a realistic cascading model for multi-sink WSNs is proposed. In this model, two load metrics are proposed to characterize the load distributions of sensor nodes and wireless links, and the cascading process of the network is jointly promoted by node overload events and link overload events, which can better reflect the cascading characteristics of multi-sink WSNs in practical scenarios. In addition, we focus on the cascading robustness of the network in the face of node attacks and link attacks. Through extensive experiments, we found that there are critical thresholds for both node capacity and link capacity, which can determine whether capacity expansion is helpful; there is a critical threshold for network load distribution, which can determine whether cascading failures occur; node attacks are more likely to trigger cascading failures than link attacks; increasing node capacity can more effectively reduce the damage of cascading failures to the network. The discovery of the above results can provide theoretical guidance for users to build a more robust multi-sink WSN against cascading failures.

Mice flow aggregation approach for Green networking

Studies have shown that most of the flows in data centres are mice flows and last short time. However, existing green networking solutions do not consider this traffic characteristic. A mass of mice flows may be rerouted after network equipment is put into sleep mode and this can result in significant degradation of network performance. In this study, the authors propose a novel solution for green networking called energy-efficient flow scheduling approach (EFSA). EFSA aggregates mice flow into a minimal set of links, and the largest flows that result in an overload of links in the set are rerouted in time. Instead of managing every mice flows, only a few numbers of largest flows are rerouted. Unused switches/links will be put into sleep mode for energy saving. The evaluation of EFSA shows that it can significantly reduce the number of rerouted flows and improve the performance of data centre networks while saving network energy efficiently.

Service traffic engineering: Avoiding link overloads in service chains

Emerging technologies such as software defined networks (SDN) and network function virtualization (NFV) enable flexibility in operation and a significant reduction of the costly hardware deployment in networks and improve service agility too. Virtual network functions (VNF) are running as virtual machines on servers, and are organized in chains using service function chaining (SFC). Though many SFC algorithms were introduced, they mostly neglect the state of the underlying networking layers and infrastructure, considering static costs for the connections among the VNFs. In this paper, we apply a model that considers also the topology and current load information of the IP layer below. We formulate the problem using an integer linear program (ILP) and propose also a heuristic algorithm with the objective of avoiding link overloads in the networking layer. Thus, we solve the stated VNF-SFC problem similar to the basic traffic engineering (TE) problem in networks. We define different architectures to classify the solutions according to the amount of networking layer information applied in VNF-SFC solutions. We analyze the operation of the proposed solutions and show their benefits and drawbacks by numerical results of a case study.

On the Interplay of Link-Flooding Attacks and Traffic Engineering

Link-flooding attacks have the potential to disconnect even entire countries from the Internet. Moreover, newly proposed indirect link-flooding attacks, such as ``Crossfire'', are extremely hard to expose and, subsequently, mitigate effectively. Traffic Engineering (TE) is the network's natural way of mitigating link overload events, balancing the load and restoring connectivity. This work poses the question: Do we need a new kind of TE to expose an attack as well? The key idea is that a carefully crafted, attack-aware TE could force the attacker to follow improbable traffic patterns, revealing his target and his identity over time. We show that both existing and novel TE modules can efficiently expose the attack, and study the benefits of each approach. We implement defense prototypes using simulation mechanisms and evaluate them extensively on multiple real topologies.

Power Control and Soft Topology Adaptations in Multihop Cellular Networks With Multi-Point Connectivity

The LTE standards account for the use of relays to enhance coverage near the cell edge. In a traditional topology, a mobile can either establish a direct link to the base station (BS) or a link to the relay, but not both. In this paper, we consider the benefit of multipoint connectivity in allowing User Equipment (UEs) to split their transmit power over simultaneous links to the BS and the relay, in effect transmitting two parallel flows. We model decisions by the UEs as to: (i) which point of access to attach to (either a relay or a relay and the BS or only the BS); and (ii) how to allocate transmit power over these links so as to maximize their total rate. We show that this flexibility in the selection of points of access leads to substantial network capacity increase against when nodes operate in a fixed network topology. Individual adaptations by UEs, in terms of both point of access and transmit power, are interdependent due to interference and to the possibility of over-loading of the backhaul links. We show that these decisions can converge without any explicit cooperation and derive a closed-form expression for the transmit power levels.

Improving the Network Load Balance by Adding an Edge

Some previously proposed ways of improving the network load balance are reducing the link overload or reducing the node overload. Traffic load of a node or traffic load of a link can be characterized by betweenness of the node or betweenness of the edge respectively. Congestion mainly happens on nodes with maximum betweenness, so one way to improve the network load balance is mainly to minimize the maximum betweenness of node in the network. We present four edge addition strategies to minimize the maximum node betweenness by adding an edge. We do experiments on three benchmark networks to verify the effectiveness of the four edge addition strategies. By analyzing the experimental results, we confirm that adding an edge at the suitable location in the network can significantly minimize the maximum betweenness of node and improve the network load balance. It is very useful to mitigate the heavy burden of the most congested router only by adding one link with small cost without changing the network topology massively. Also, our work is helpful for service providers to optimize their network performance by adding an edge or to make good network planning by optimizing the existing network topology incrementally.

Precedence-enabled per-hop behaviour: impact on TCP and UDP flows

The author proposes and analyses an approach to support both precedence and preemption (P&P) and QoS handling in common packet transport infrastructures. Precedence has to do with the relative importance of the information content, whereas preemption has to do with mechanisms to deny lower precedence traffic access to network resources in favour of higher precedence traffic, when necessary. The author's approach to this duality is to enhance active queue management (AQM) techniques to provide P&P capabilities and rely on standard, well-studied QoS schedulers, for example, Weighted Round Robin, Class-Based Weighted Fair Queuing, etc., for handling QoS requirements. The present scheme allows low-order queues (within the context of QoS handling) to plead up to the next higher-order queue for help in alleviating queue congestion under periods of communication link overload. The scheme is referred as the cross-queue-AQM (CQ-ACM) scheme and can be extended to higher numbers of queues and any type of scheduler. Through extensive simulation studies, the performance of CQ-AQM scheme under heavy traffic limits is investigated, where preemption is required. The performance metrics of interest to this analysis are packet delay, packet loss and throughput as a function of the packet QoS class and P-L. Further, two new metrics of merit, Gain and System Efficiency, are defined, which are specific to P&P considerations. The studies concentrated on both flow-controlled and non-flow-controlled traffic, as well as mixed traffic conditions. Simulation results show that the algorithms perform extremely well for all cases studied.

An Inquiry-led Personalised Navigation System (IPNS) using multi-dimensional linkbases

The simplicity of the hypertext model behind the World Wide Web is a factor in its success, but this simplicity brings limitations. One of these limitations is embedding links in documents. Open Hypermedia addresses this by instead storing them in separate link databases. Meanwhile, the Adaptive Hypermedia approach seeks to enhance a user's experience by inserting personalised additional content and links on the web page. However, these techniques do not offer the user any control over the adaptation. In this paper, we propose the concept of a multi-dimensional linkbase for adaptive links presentation. Links are created and stored in a single, multi-dimensional, linkbase that provides presentation links based on the user's preferences and profile. We present a web-based system Inquiry-led Personalised Navigation System that implements this multi-dimensional concept for controlling its personalisation of hyperlinks. We give the results of our evaluation, which confirm that user-controlled adaptation is a satisfactory approach to providing users with control over personalisation, and can alleviate the link overload problem.

Optimal transport on complex networks

We present a heuristic algorithm for the optimization of transport on complex networks. Previously proposed network transport optimization algorithms aim at avoiding or reducing link overload. Our algorithm balances traffic on a network by minimizing the maximum node betweenness with as little path lengthening as possible, thus being useful in cases when networks are jamming due to node congestion. By using the resulting routing, a network can sustain significantly higher traffic without jamming than in the case of shortest path routing.

Increasing Internet Capacity Using Local Search

Open Shortest Path First (OSPF) is one of the most commonly used intra-domain internet routing protocol. Traffic flow is routed along shortest paths, splitting flow evenly at nodes where several outgoing links are on shortest paths to the destination. The weights of the links, and thereby the shortest path routes, can be changed by the network operator. The weights could be set proportional to the physical lengths of the links, but often the main goal is to avoid congestion, i.e. overloading of links, and the standard heuristic recommended by Cisco (a major router vendor) is to make the weight of a link inversely proportional to its capacity. We study the problem of optimizing OSPF weights for a given a set of projected demands so as to avoid congestion. We show this problem is NP-hard, even for approximation, and propose a local search heuristic to solve it. We also provide worst-case results about the performance of OSPF routing vs. an optimal multi-commodity flow routing. Our numerical experiments compare the results obtained with our local search heuristic to the optimal multi-commodity flow routing, as well as simple and commonly used heuristics for setting the weights. Experiments were done with a proposed next-generation AT&T WorldNet backbone as well as synthetic internetworks.

A nonlinear emergency control strategy for HVDC transmission systems

A novel nonlinear emergency control method for HVDC transmission systems is presented in this paper. First, an observation-decoupled state space model of AC and DC interconnected power systems, which allows estimation or computation of the state components from local measurements, is developed. Secondly, the nonlinear control rules of HVDC links are derived using optimal-variable-aim strategy, which not only improves the first-swing stability, but also effectively damps the subsequent power oscillation. Finally, the simulation results of a three-machine six-bus system show that the proposed method can enough use the capabilities of fast response and short-time overload of HVDC links to improve the transient stability of power systems.