Computer Networks

In this paper a mathematical model for predicting traffic in computer networks based on heterogeneous differential equations describing the oscillatory motion was proposed. It is suggested that the solution to the equation should be modified on the basis of the sum of Dirac functions which have different arguments at different points of time to simulate bursts of network traffic. Based on this model, the software implementing network monitoring and forecasting of traffic on the network on the grounds of mathematical calculations and collected data was developed. Testing of models based on real network data from LPNU ACS Department was presented. Also, the simulation results have been compared with real traffic data. The results are illustrated in the form of both tables and plots.

Nowadays, many IT products are created as distributed solutions that consist of many parts, such as mobile applications, web-based back-ends, as well as APIs that connect various parts of the system. It is a crucial task to apply a suitable architecture to provide users of mobile applications with satisfactory operation, especially when the Internet connection is necessary to get or send some data. The simulation of network architecture and configuration using a high-level model of the system described with dedicated Domain-Specific Language (DSL), enabled by the Timed Colored Petri Nets (TCPNs) formalism is a beneficial approach that could be applied in real case studies. The already proven research method has been applied to one of the scenarios regarding the system offered by TITUTO Sp. z o.o. [Ltd.] company (Rzeszow, Poland). The first obtained results were not sufficiently precise for detailed analysis of the system. Thus, the case study was used to improve the simulation method in order to more accurately model data transmissions over the network. After modifications were implemented in the simulation tool, significantly better results have been received, as discussed in the paper.

In the paper, the method for determining the diagnostic structures for effective fault detection within military IoT networks is proposed. The method is based on partitioning IoT network among disjoint clusters and applying comparison approach for diagnosis of misbehaving nodes within network clusters. Common communication and diagnostic structures are determined on the basis of the nodes attainability characteristics and subsequent generation of subset of dendrites. The procedure for choosing the most effective diagnostic structures is proposed in the paper. In the procedure for selecting the diagnostic structure the following measures are used: the global dendrite attainability, the number of elementary comparison tests and the number of stages for performing all required tests. Also, influence of diagnostic tests on the values of performance metrics for some real-time services is investigated. The usefulness of the method has been verified through simulation experiments prepared and performed in Riverbed Modeler environment.

This paper proposes a new joint power control and resource allocation algorithm in cognitive LTE femtocell networks. The presented algorithm minimizes the transmit power of each femtocell, while satisfying a maximum number of users with QoS requirements. The optimization problem is multi-objective NP-hard. Hence, in the paper a joint channel assignment and power control allocation scheme is proposed, solving the problem so formulated. Especially, a Gale-Shapley method is involved in this scheme to address the co-tier femtocell interference issue. In order to find a pareto optimal solution, a weighted sum is used. The performance of this method is evaluated by simulation.

The growing number of mobile devices and the popularity of Internet of Things (IoT) applications have caused an increase of local-area location-aware protocols and applications. Localization has become a popular topic in the literature and many localization algorithms in wireless sensor networks (WSN) have been proposed. However, the most of them are vulnerable to common wireless attacks. In this article, we introduce the secure localization protocol based on a RSSI-mapping, which uses symmetric cryptography. The security attributes of the protocol have been proved using the Scyther tool. We present the experimental results that demonstrate the ability to estimate sensor’s location in the environment, where other networks are available. The results show, that the introduction of security mechanisms to localization protocols may significantly increase the execution time and exceed strict time restrictions in some real-time applications. Nevertheless, the existence of insecure protocol in hostile environment is unacceptable. To achieve a better efficiency, we suggest to use the hardware encryption provided in CC2420 radio chip.

The paper presents the evaluation of the GQP algorithm in AMI networks using real map based network topologies (low, medium and high density of buildings). The algorithm was compared to the reference algorithms: CB, SBA and DP. It was shown that the GQP algorithm presents the good scalability, relatively optimal number of selected forwarders and by introducing the redundancy factor, good fault tolerance. An improvement to GQP algorithm to add a redundancy factor is proposed, what allows to execute fault tolerant broadcast transmission.

In this study, performances of classification algorithms N-Nearest Neighbors (N3) and Binned Nearest Neighbor (BNN) are analyzed in terms of indoor localizations. Fingerprint method which is based on Received Signal Strength Indication (RSSI) is taken into consideration. RSSI is a measurement of the power present in a received radio signal from transmitter. In this method, the RSSI information is captured at the reference points and recorded for creating a signal map. The obtained signal map is knows as fingerprint signal map and in the second stage of algorithm is creating a positioning model to detect individual’s position with the help of fingerprint signal map. In this work; N-Nearest Neighbors (N3) and Binned Nearest Neighbors (BNN) algorithms are used to create an indoor positioning model. For this purpose; two different signal maps are used to test the algorithms. UJIIndoorLoc includes multi-building and multi floor signal information while different from this RFKON includes a single-building single floor signal information. N-Nearest Neighbors (N3) and Binned Nearest Neighbors (BNN) algorithms are presented comparatively with respect to success of finding user position.

Many organizations and research working groups, including among others IEEE, ITU, ETSI and IMO are currently working towards improvements in communication of different types of vehicles (cars, trains, planes and vessels) and upgrading utilities and services offered to their crews and passengers travelling all over the world. The paper deals with selected aspects of the TCP protocol connectivity in maritime wireless networks. The authors show results of measurements performed in a real-world maritime environment consisting of on- and off-shore devices and transmission systems, partly located on vessels. Based on the collected measurements, the authors provide statistical analysis, including connectivity periods and connectivity gaps observed as a result of vessels motions. The obtained statistical results were used, in turn, in a simulation test-bed to verify efficiency of TCP connections, assuming the use of Reno algorithm, together with F-RTO enhancement (Forward RTO-Recovery), Cubic algorithm, and further adjustments proposed by the authors. The results show significant increase of the average throughput (up to 3 times) and decrease of the average download time (up to 53%), as compared to the pure Reno TCP solution. The proposed modifications seem to be especially important and attractive for highly unreliable wireless links - expected to be very common in a maritime environment.

The paper presents path loss model for a WSN in an open space on the basis of measurements. The measurements were performed in different weather conditions i.e. temperature and humidity in agricultural area. Theoretical path loss models are always flawed because of their exponential relationship. This causes an increase in error during the localization process. Thus, the determination of the path loss exponent constant based on measurement results become so important. The study focused on designation of the path loss model for different weather conditions. The influence of the temperature and the humidity on the RSSI distribution was analysed.

New Internet threats emerge on daily basis and honeypots have become widely used for capturing them in order to investigate their activities. The paper focuses on a detailed analysis of the behavior of various attacks agains 7 Linux–based honeypots. The attacks were analyzed according to the threat type, session duration, AS, country and RIR of the attack origin. Clusters of similar objects were formed accordingly and certain typical attack patterns for potential detection automation as well as some aspects of threat dissemination were identified.

In the paper, we present enhancements of the encryption method for secure data transmission used in Secure Data Exchange method (SDEx) [1–3]. Potential weaknesses and possible attacks have been previously described in [4]. The new version of the encryption method is immune to indicated in [4] vulnerabilities connected with the potential knowledge of the part of the original message and uneven distribution of bits in the message blocks. In the new solution, we use also Davies-Meyer scheme in order to enhance immunity to meet-in-the-middle attacks.

For many years the detection of malware and preparation of the ways of preventing them have been treated as two distinct issues. Malware monitoring should provide information on how to detect the presence of malware and attempts to infect the system. The protecting systems using this information should identify and stop malware operation. This paradigm led to current solutions, where protecting systems focus on detection of incoming threats and do not pay attention on the presence of not previously detected malware in the system. Malware authors have developed various methods of circumventing the defense lines of protecting systems, what results in a growing stream of information of systems security breaches. This indicates the need for additional line of defense, focused on detection of the malware, which penetrated defenses of the system. The paper presents the concept of such additional defense line, discusses the sources of necessary informations, method for detection of unknown malware and possible method of blocking malware operation.

Thanks to its ability to face unknown attacks, anomaly-based intrusion detection is a key research topic in network security. In this paper anomalies are addressed from an Information theory perspective: in a nutshell, it is assumed that attacks determine a significant change in the distribution of relevant traffic descriptors and this change is measured in terms of Shannon entropy. In more detail, the traffic is first aggregated by means of random data structures (namely three-dimensional reversible sketches) and then the entropy associated to different traffic descriptors (for sake of brevity, we focus on the numbers of flows and bytes) is computed by using two alternative constructions of the corresponding empirical distributions, one based on the flows destination address and the other on their volume. The experimental results obtained over the MAWILab dataset validate the system and demonstrate the relevance of the way in which the histogram is built.

A new information technology for botnets detection based on the analysis of the botnets’ behaviour in the corporate area network is proposed. Botnets detection is performing combining two ways: using network-level and host-level analysis. One approach makes it possible to analyze the behaviour of the software in the host, which may indicate the possible presence of bot directly in the host and identify malicious software, and another one involves monitoring and analyzing the DNS-traffic, which allows making conclusion about network hosts’ infections with bot of the botnet. Based on this information technology an effective botnets detection tool BotGRABBER was constructed. It is able to detect bots, that use such evasion techniques as cycling of IP mapping, “domain flux”, “fast flux”, DNS-tunneling. Usage of the developed system makes it possible to detect infected hosts by bots of the botnets with high efficiency.

Redundancy is the main method for achieving high reliability level in networked control systems NCSs. It is often applied in network interfaces in order to maintain operability of communication subsystems even when faults occur. In most cases, redundant communication buses realize exactly the same functionality as the initial non-redundant bus. That makes the system more reliable but the additional throughput of the redundant buses is not exploited even if the system condition would allow it. The idea of taking advantage of that throughput had made the authors to work on multi-network interface node which on the other hand maintain the high reliability of the communication subsystem, and on the other, makes it possible to manage the additional communication resources more efficiently, and therefore increases some parameters of the communication network.

With the spread of Dynamic Adaptive Streaming over HTTP (DASH) systems, appeared the problem related to the resources management in end-users’ networks. The article proposes a new solution for the distribution of Scalable Video Coding (SVC) video streams in home networks. It relies on a Software Defined Network (SDN) controller, which based on the parameters of transmitted SVC video and the usage status of network resources allows for dynamic traffic shaping. At the same time, it was assumed that the proposed solution is compatible with Server and Network Assisted DASH (SAND) standard and its implementation is possible without the use of additional, dedicated hardware. The article presents the analysis of influence of proposed SDN on the improvement of the SVC video quality received by DASH clients in a typical home network. Test results confirm the superiority of the proposed system over the conventional solutions.

In this paper the connectivity is analysed of vehicular ad hoc networks (VANETs) in arterial roads with signalised intersections. A method is proposed to derive an estimate of minimum transmission range (MTR), i.e., a minimum value of the vehicles transmission range that allows all vehicles in a given road section to be connected via multihop communication. The introduced method takes into account the impact of traffic signals coordination on formation of vehicle platoons. It is applicable for both the under-saturated and the over-saturated traffic conditions. The main contribution in this paper is formulation of a relationship, which allows the upper bound of MTR to be estimated for VANETs in unidirectional and bidirectional signalized arterial roads. The conducted experiments confirm that the derived estimate fits well with results of simulation experiments.

This article verifies the applicability of the convolution algorithm for modelling multi-service network systems with different call streams, including non-Poissonian streams. The study includes investigations of traffic streams that are state-dependent and independent. The service time is determined by the following distributions: Pareto, uniform, gamma, normal and exponential. The results of the simulation experiments are compared with the results of modelling by convolution algorithm. The results obtained in this study allow limits for the applicability of the convolution algorithm to be determined and identified.

The recent innovations in connecting hardware and smart encoding schemes make it possible the old copper installations are capable to support T1/E1 bit rates. It is obvious that old networks destined for POTS, will intensively dissipate energy transmitted by new wideband services and they should be regarded as a potential source of electromagnetic hazards. This note reports results of the study towards developing a computer-aided method for numerical modeling of an electromagnetic environment in a close vicinity of cables carrying signals of wideband transmission systems. The proposed method is formulated in the frequency domain and uses multiconductor transmission line theory for determination of field sources. Subsequently, fullwave approach is applied to find near electromagnetic field in the vicinity of the cable.

Last years, videoconferencing systems are rapidly evolving and they are becoming more and more popular as a real time communication tool among users. A technology such as VoIP can be used in conjunction with desktop videoconferencing systems to enable low-cost face-to-face business meetings without a necessity to travel, especially for internationally oriented companies that have offices all around the word. In this paper, we focus on and discuss a videoconferencing platform based on the WebRTC technology. We analyze an impact on the multiplexing server’s CPU load and memory requirements for different number of communicating users while taken into account different HW/SW configurations of end-point devices.

In the paper, a new analytical model of multi-service communication networks with traffic overflow is elaborated. It is assumed that both: primary resources and alternative resources, forming networks with traffic overflow, are distributed, as, e.g. in mobile networks in which traffic from a group of 4G cells is overflowed to a group of 3G cells. The paper proposes also a new method for determining parameters of multi-service traffic that overflows from the distributed primary resources to the distributed alternative resources, as well as a method for occupancy distribution calculation and blocking probability calculation in the alternative resources servicing overflow traffic. The results of the analytical calculations are compared with the results of the simulation experiments of some selected structures of overflow systems with the distributed primary and alternative resources.

Traditional networks are often quite static, slow to modify, dedicated for a single service and very difficult to scale, what is typical for a large number of different network devices (such as switches, routers, firewalls, and so on), with many complex protocols implemented or embedded on them. Software Defined Network (SDN) is a new technology in communication industry that promises to provide new approach attempting to overcome this weakness of the current network paradigm. The SDN provides a highly scalable and centralized control architecture in which the data plane is decoupled from the control plane; this abstraction gives more flexible, programmable and innovative network architecture. However, centralization of the control plane and ability of programming the network are very critical and challenging tasks causing security problems. In this paper we propose a framework for securing the SDN by introducing an application as an extension to the controller to make it able to check every specific flow in the network and to push the security instructions in real-time down to the network. We also compare our proposal with other existing SDN-based security solutions.

The analyses of the ping-pong communication paradigm anticipated possibility to undetectably wiretap some variants of quantum direct communication. The only proposed so far instantiation of attacks of this type is formulated for the qubit based version of the protocol and it implicitly assumes the existence of losses. The essential features of undetectable attack transformations are identified in the study and the new generic eavesdropping scheme is proposed. The scheme does not refer to the properties of the vacuum state, so it is fully consistent with the absence of losses assumption. It is formulated for the space of any dimension and it can be used to design the family of circuits that enable undetectable eavesdropping.

The chapter contains information about a construction of quantum switch for qutrits. It is an expansion of the idea of quantum switch for qubits. For the networks based on quantum effects the switch could realize an operation of changing the direction of transferred information. A presented definition of quantum switch may be easily generalized to qudits. The chapter contains also the figures representing circuits realizing the quantum switch and a proof of its correctness. Additionally, there is an analysis of entanglement level in the circuit which also characterizes the correct operating of the switch.

Cloud service providers mostly offer service level agreements (SLAs) in descriptive format which is not directly consumable by a machine or a system. Manual management of SLAs with growing usage of cloud services can be a challenging, erroneous and tedious task especially for the cloud service users (CSUs) acquiring multiple cloud services. The necessity of automating the complete SLA life cycle (which includes SLA description in machine readable format, negotiation, monitoring and management) becomes imminent due to complex requirements for the precise measurement of quality of service (QoS) parameters. In this work, the complete SLA life cycle management is presented using an extended SLA specification to support multiple CSU locations. A time efficient SLA negotiation technique is integrated with the extended SLA specification for concurrently negotiating with multiple cloud service providers (CSPs). After a successful negotiation process, the next major task in the SLA life cycle is to monitor the cloud services for ensuring the quality of service according to the agreed SLA. A distributed monitoring approach for the cloud SLAs is elaborated, in this work, which is suitable for services being used at single or multiple locations. The discussed monitoring approach reduces the number of communications of SLA violations to a monitoring coordinator by eliminating the unnecessary communications. The presented work on the complete SLA life cycle automation is evaluated and validated with the help of experiments and simulations.

In this paper, a performance model is used for studying distributed web systems (an J2EE web application with Oracle backend-database). Performance evaluation is done by obtaining load test measurements. Queueing Petri Nets (QPN) formalism supports modeling and performance analysis of distributed World Wide Web environments. The proposed distributed web systems modeling and design methodology has been applied for evaluation of several system architectures under different external loads. Experimental analysis is based on benchmark with realistic workload. Furthermore, performance analysis is done to determine the system response time.

In this paper the performance of fractional order PID controller as AQM mechanism and impact of traffic self-similarity on network utilization are investigated with the use of discrete event simulation models. The researches show the influence of selection of PID parameters and degree of traffic self-similarity on queue behavior. During the tests we analyzed the length of the queue, the number of rejected packets and waiting times in queues. In particular, the paper uses fractional Gaussian noise as a self-similar traffic source. The quantitative analysis is based on simulation.

In this work, the fluid limit approach methodology is applied to find a sufficient and necessary stability condition for the Basic Collaboration (BC) system with feedback allowed, which is a generalization of the so-called W-model. In this queueing system, some customer classes need cooperation of a subset of (non-overlapping) servers. We assume that each customer class arrives to the system following a renewal input with general i.i.d. inter-arrival times, and general i.i.d. service times are also assumed. Priority is given to customer classes that can not be served by a single server but need a cooperation.

We investigate the $$M/G/n\le \infty /(0,V)$$-type Erlang loss service system with $$n\le \infty $$ independent service stations and Poisson arrival stream in which volumes of entering demands and their processing times are generally distributed and, in general, are dependent random variables. Moreover, the total volume of all demands present simultaneously in the system is bounded by a non-random value V (system memory capacity). The enqueueing process is controlled by an AQM-type non-increasing accepting function. Two different acceptance rules are considered in which the probability of acceptance is dependent or independent on the volume of the arriving demand. Stationary queue-size distribution and the loss probability are found for both scenarios of the system behavior. Besides, some special cases are discussed. Numerical examples are attached as well.

We investigate queueing systems with demands of random space requirements and limited buffer space, in which queueing or sojourn time are limited by some constant value. For such systems, in the case of exponentially distributed service time and Poisson entry, we obtain the steady-state demands number distribution and probability of demands losing.

Electrical and electronic systems have been getting raising importance for innovations in the automotive industry. Networking issues are a key factor in this process since they enable distributed control functions and user interaction bringing together nodes from different vendors. This paper analyses available and emerging network technologies for in-vehicle communication from a requirements driven perspective. It reviews successful network technologies from other application areas regarding a possible deployment in vehicular communication and distinguishes passenger car and commercial vehicle sectors as far as possible. This contribution is oriented to the OSI reference model showing the state of the art and future opportunities at the level of the several communication layers with a focus on physical layer issues and medium access protocols and including information modeling aspects.

Indoor Positioning Systems are more and more attractive research area and popular studies. They provide direct access of instant location information of people in large, complex locations such as airports, museums, hospitals, etc. Especially for elders and children, location information can be lifesaving in such complex places. Thanks to the smart technology that can be worn, daily accessories such as wristbands, smart clocks are suitable for this job. In this study, the earth’s magnetic field data is used to find location of devices. Having less noise rather than other type of data, magnetic field data provides high success. In this study, with this data, a positioning model is constructed by using Artificial Neural Network (ANN). Support Vector Machines(SVM) was used to compare the results of the model with the ANN. Also the accuracy of this model is calculated and how the number of hidden layer of neural network affects the accuracy is analyzed. Results show that magnetic field indoor positioning system accuracy can reach 95% with ANN.

Elements of cloud infrastructure like load balancers, instances of virtual server (service nodes), storage services are used in an architecture of modern cloud-enabled systems. Auto scaling is a mechanism which allows to on-line adapt efficiency of a system to current load. It is done by increasing or decreasing number of running instances. Auto scaling model uses a statistics based on a standard metrics like CPU Utilization or a custom metrics like execution time of selected business service. By horizontal scaling, the model should satisfy Quality of Service requirements (QoS). QoS requirements are determined by criteria based on statistics defined on metrics. The auto scaling model should minimize the cost (mainly measured by the number of used instances) subject to an assumed QoS requirements. There are many reactive (on current load) and predictive (future load) approaches to the model of auto scaling. In this paper we propose some extensions to the concrete reactive auto scaling model to improve sensitivity to load changes. We introduce the extension which varying threshold of CPU Utilization in scaling-out policy. We extend the model by introducing randomized method in scaling-in policy.

This paper presents a solution of the problem of the route calculation for garbage removal trucks. The entire system architecture including algorithms of the route calculation, server and client part software, electronic devices on the garbage containers, mobile solution and collaboration with other routing services is presented. The dynamic network model and the optimization criterion on containers status and road traffic as well as the knowledge base which form the hybrid control system responsible for time of the garbage collection are introduced.

The rising number of vehicles and slowly growing transport infrastructure results in congestion issue. Congestion becomes an important research topic for transportation and control sciences. The recent advances in vehicular ad-hoc networks (VANETs) allow the traffic control to be tackled as a real-time problem. Recent research works have proven that the VANET technology can improve the traffic control at the intersections by dynamically changing sequences of traffic signals. Transmission of all vehicle positions data in real-time to a traffic lights controller can generate a significant burden on the communication network, thus this paper is focused on the reduction of data transmitted to a control unit by vehicles. The time interval between data transfers from vehicles is defined by zones that are tuned for a given traffic control strategy using the proposed algorithm. The introduced zone-based approach reduces the number of transmitted messages, while maintaining the quality of traffic signal control. The results of experiments firmly show that the proposed method can be successfully used for various state-of-art traffic control algorithms.