Computer Networks

This paper describes the method of orchestrating behavior of two discrete-event simulators: Timed Colored Petri Net (TCPN) simulator and popular Ns-2. The simulators are connected to provide reliable model of distributed systems based on TCPN formalism supported with precise TCP model from the Ns-2, based on real implementation. Consequently, precise results of network transmission time estimation can be combined with reliable model of distributed application in order to obtain credible estimations of its efficiency on the basis of simulation. Data passing interface together with clock synchronization algorithm is described and discussed. Results of experiments are compared with simulations.

The online Data Acquisition system of the Compact Muon Solenoid (CMS) experiment at CERN’s Large Hadron Collider is designed to collect data corresponding to a single collision of particles, referred to as an event, from about 500 detector Front-Ends. Each of those Front-Ends delivers event-fragments of an average size of 2 KB at a rate of 100 kHz. The event-fragments are statically distributed (usually in round robin fashion) between 8 identical computing farms, which construct the whole events. In this paper we present experimental results of employing a distributed, asynchronous load scheduling algorithm in place of the static event allocation mechanism. The research focuses in particular on balancing the event flow in case of degradations in computing power or network throughput. The discussed studies prove that the proposed method meets the requirements of CMS experiment and has a positive impact on the resource utilization and overall fault tolerance.

Distributed processing is an important issue of numerical calculations, in particular concerning the problems of time-consuming calculations. Solving this problem requires appropriate software, which is more complicated than the implementation in parallel environments. This article presents a proposal of distributed processing solution based on web browsers. This method, unlike the commonly used, does not require installing any software on the compute nodes. This is achieved through the distribution and execution of the code in the container, which is a web browser.

The paper presents the study of the traffic nature collected from APRS port in AX.25 network. Theoretical foundations of stochastic self-similar processes are presented. Four samples of collected traffic are analysed for the presence of self-similarity; the research used two common methods:

R

/

S

method and variance analysis method. The article ends with conclusions based on correlations found in the study.

Traffic’s periodic processes in computer networks based on Ateb-functions without perturbation were simulated. The types of small perturbations that influence the traffic’s vibration were considered. Appropriate software that outputs the results in graphical and tabular forms was developed.

In recent years we saw, how desirable is possibility of mobile communications in modern society. The consequence of this is to have Internet more reliable and predictable in context of Web access. Thus, there is a need to analyzing Web server’s performance and trying to predict future demand on given server’s. This kind of research requires spatial methods of analysis of such data. Therefore we decided using spatial econometrics methods to explore Web server’s performance.

This paper contains description the spatial regression models: Classic Regression Model (CRM), Spatial Lag Model (SLM) and Spatial Error Model (SEM). We use these models to predict total download time of data from Web servers. The real-life dataset was obtained in active experiments performed by the Multiagent Internet Measurement System (MWING), which monitored web transactions issued by MWING’s agent located in Gdańsk, Poland and targeting Web servers in Europe. Data analyzed in this paper contains the measurements, which were taken every day at the same time: at 6:00 a.m., 12:00 a.m. and 6:00 p.m. We presented our analysis of measurement data and created spatial econometric models. Next, influences on prediction errors in regression models were described. After that we compared econometric with geostatistical methods. At the end, conclusions and future research directions to Web performance predictions were given.

This paper presents the Turning Bands method (TB) as a geostatistical approach for making spatio-temporal Web performance analyses and forecasts. The first part of this paper briefly introduces and characterizes the Multiagent Internet Measuring System (MWING) whose main task involves collecting data necessary for making the aforementioned analyses and forecasts. MWING comprises of many agents located in different parts of the globe; however, for the purpose of this paper the data that had been collected only by the agent in Wrocław were used. The measurements were taken every Monday in two periods: the first, three times a day (at 6:00 am, 12:00 pm and 6:00 pm), between 1 February 2009 and 28 February 2009; the second, at the same hours, but between 1 December 2012 and 24 December 2012. The subsequent part of this paper briefly elucidates TB algorithm; the final part commences with data analysis which is followed by presenting sample analyses and forecasts of web servers performance made using TB.

The Local Minimum Problem occurs in geographic routing scenarios. In this paper two solutions to this problem for certain network topologies are proposed. By using the notion of virtual coordinates a theoretical and a practical constructions are presented. A distributed algorithm for the practical approach is proposed.

Many theoretical works focus on maximizing the lifetime of a measurement-gathering sensor networks by researching different aspects of energy conservation or details of self-organizing network algorithms. In our practical deployment of such a network we learned that software and hardware reliability, as well as anticipation of worst-case scenarios, are the equally important factors for successful experiments. We describe our experiences with implementing a WSN for long-time unattended operation in a greenhouse data-collecting application.

The growing popularity of wireless sensor networks increases the need for optimal and energy efficient routing protocols. Among many hierarchical routing protocols, the one which is really worth noticing is the Low Energy Adaptive Clustering Hierarchy (LEACH) protocol. Because of its simplicity and distributed operation it has been used as a base for several further protocols such as PEGASIS, HEED, TEEN and APTEEN. This article presents an analysis of the LEACH protocol and suggests a modification to improve its effectiveness by far.

Performance analysis of the 802.11 EDCA and DCF using simulation and analytical model is presented. An impact of different number of ACs in the network performance is studied under nonsaturation and saturation network condition. Additionally, it is shown that the EDCA doesn’t provide a good prioritized access in contrast to the DCF, when only one traffic type is being transmitted through the wireless network.

Battery-powered nodes have limited energy reserves therefore applications and protocols used for WSNs, should be designed, concerning the optimized energy consumption in order to prolong the network lifetime. Data reception and transmission are the main energy consuming operations and they are regulated by the network layer, hence the routing protocol plays very important role in network optimization.

In this paper information concerning the LEACH routing protocol is gathered and the classification of LEACH-based modifications is presented. Furthermore this paper focuses on improvements to the LEACH protocol that address problems of the cluster head selection, load balancing and lifetime enhancement as well as presents the simulation results for the selected group of LEACH-based protocols.

In this paper, we study proper routing protocols for border surveillance missions using wireless sensor networks (WSNs). We assume that the sensor nodes are equipped with ZigBee transceivers for wireless communications. Three well known routing algorithms (AODV, DSR, and OLSR) are simulated in a WSN surveillance scenario. The performances of these routing algorithms are compared in terms of traffic load, delay, packet loss, and energy consumption. Our results indicate that DSR performs better than other algorithms for border surveillance applications. Moreover, a novel algorithm called “DSR_OP” is proposed for improving DSR routing in terms energy management in the network and extending the network life time. However Comparisons of WSN routing protocols (DSR, AODV, OLSR and others) are presented since many years ago, but there is no simulation with OPNET, so our novelty is that the validity of proposed method and the comparisons are confirmed by simulations in OPNET.

In IT systems quantitative risk analysis is a method for security risk assessment used as a part of risk management process which in turn is a part of security policy. The main advantage of the method (in comparison to other techniques) is its accuracy – a better start point for security policy definition. Obviously the accuracy is directly related to input data dependability. The basic problem of the method is related to acquisition of input data necessary to perform the analysis. Data should be complete and reliable. The main purpose of the paper is to define comprehensive set of data necessary for the quantitative risk analysis for data storage systems (including magnetic disks and solid state disks) and to discuss trustworthiness of the data. Such comprehensive set of data should include data related to storage technology, features of storage processes (e.g. compression, deduplication), security events probabilities. Some of the parameters are dynamic, they change in time, they are related to environmental conditions. Different sources, different means of data acquisition are presented together with discussion on trustworthiness and dependability of the acquired data in the second part of the paper.

Web traffic anonymization is hiding the originator of the web request. Although is required in some circumstances, such feature is not included in the WWW service. Anonymization can be reached using various commercial and public domain tools. The obvious adverse aspect of anonymization is the significant slowing down of the anonymized traffic compared to the normal traffic. This study focuses on measurement of the parameters of such slowing down (in terms of transmission speed and latency). This study is based on previous studies concluding that TOR (The Onion Routing) is the best available free web anonymization tool. Nevertheless the TOR’s cost of operation in terms of response time increase is still too high so the main goal of this paper is to find ways how to make them lower. The extensive set of WWW pages and files was formed and the latency and response time during their download was measured repeatedly both with anonymization in various configurations and without it. The result showed that there are some ways how to improve the TOR efficiency but despite them the cost still remains too high for ordinary use.

A new botnet technique based on multi-agent system with the use of fuzzy logic is proposed. The analysis of the botnets’ actions demonstrations in the situation of the intentionally computer system reconnection with the use of fuzzy logic is performed. Fuzzy expert system for making conclusion of botnet presence degree in computer systems is developed. It takes into account the demonstration degree of reconnected computer system, demonstration degree of probably infected computer systems and demonstration degree of other computer systems available in the corporate area network that probably weren’t infected.

Contemporary malware authors attempt many ways to make its products “invisible” for antymalware programs, and after infection deeply conceal its operation from users sight. The presence of concealed malware can be detected many ways. Most of them operate “on demand” and provides high scanning overload of the system, blocking the chances for normal users operation. The paper presents new method of rootkit operation detection, suitable for continuous operation, based on the analysis of network activity pictures viewed from two sources (internal and external to system), along with the results of method tests on virtual machines infected with the selected rootkits code samples.

The paper presents the results of empirical tests, which examine the algorithm of failure detection in transmission line or network node in dual bus system. The implemented algorithm is the base that use the second bus for parallel data transmission. It also presents the research results, which refer to measuring the duration of basic transaction in the network system, duration of the bus failure detection A(B) and slave station failure.

The paper presents the considerations on the method which enables to accelerate the exchange of data in distributed control system, using multi-protocol nodes. The method presented in this paper is related to hardware and software, and based on new original communication protocol, which is used by the node for supporting various communication protocols to simultaneous data exchange via different buses. This method will enable to increase not only network bandwidth, but also the security of data transmission.

Manufacturing Execution Systems (MES) require the communication services, which allow for easy access to information processed in industrial control systems. Contemporary distributed control systems are based on the IEC 61131 and IEC 61158 standards. This situation causes a bottleneck in communication between control and MES systems. This paper deals with the problem of large data block acquisition between the distributed control system and MES. Authors have put a special focus on Master PLC – Station PLC communication realised in a distributed control system. The limited bandwidth of existing fieldbus network was used. Presented approach has been developed to support data collection process in existing distributed control system used in automotive production. Considered MES functions are related to energy efficiency analysis on machine and production line level. The OPC UA (IEC 62541) standard has been taken into account during large data block size estimation.

The paper presents a concept and implementation of Communication Performance Tests (CPT) for small distributed control systems. Requirements for the communication performance are specified using SysML notation. Test cases included in the specification are translated into a dedicated test definition language CPTest+. System implementation is then verified by executing the tests generated from the specification and analyzing results of test runs. The procedure is supported by specialized tools integrated with IEC 61131-3 development environment, including SysML model editor and CPTest testing environment.

In this paper, the authors present methods for connection Service Oriented Architecture with OPC UA to control systems. Different disciplines such as data science, communication theory and control systems have different viewpoint on the properties of communication systems. Requirements of the control systems and requirements of information systems are presented. The integration of the two systems is analysed. Problem is formulated: how it is possible to get new functionality without losing existing features. Most important parameter is time. The control systems have to achieve fixed time of data sampling, regardless of situation. For Service Oriented Architecture time is not so important. SOA emphasizes openness, modularity and compatibility. Integration of two different systems and integration problems in distributed control systems are presented and analysed.

High-quality information exchange between upper layers of the communication network (e.g. TCP, IP layers) requires reliable connection of communicating devices on the physical layer. Any non-corrected errors at this level force the upper layers to perform proper action to recover transmitted information. It reduces data throughput and increases delay to unacceptable level for some services. Among physical media, wireless one is the most hostile environment, due to its unpredictable behavior. In that case, OFDM (Orthogonal Frequency Division Multiplex) modulation and LDPC (Low Density Parity Check) error correction codes appear the best choice to provide high transmission quality on the physical layer. This paper presents the results of the authors’ simulation of a LDPC-coded OFDM system with particular emphasis on codes over high order Galois fields (non-binary) which are not commercialized yet.

In this paper, the competitive interactions of radio devices dynamically accessing the radio spectrum in the cognitive radio network are studied. The dynamic spectrum access is modelled by a game with incomplete information. The notion of incomplete information means that some players do not completely know the structure of the game. This paper provides a spectrum auction to address the problem of radio channel allocation for cognitive radio networks. The VCG auction to maximise the auctioneer’s revenue or maximise social welfare in the spectrum auction is also examined. A dynamic programming algorithm is then applied to solve the spectrum auction problem. Some simulation results are provided.

The influence of node mobility in Mobile Ad hoc NETworks (MANETs) has significant implications for system performance. A class of MANETs characterised by a sparse density of nodes coupled with a relatively short range of radio communication, results in a network topology that is disconnected most of the time.This wireless mobile ad hoc network is called an “opportunistic network” or “delay-tolerant” network. This paper presents some models in which the rate of information propagation within the opportunistic network is considered. Furthermore, a characterisation of the multicast time in the opportunistic network is developed.

In Wireless Optical Systems (WOS), Multi-pulse Pulse Position Modulation and Differential Pulse Position Modulation are two famous modulation schemes compatible with free space optical communication system. In this paper we present a modified form of the existing DPPM based on MPPM coding, called Differential Two-Pulses Position Modulation (D2PPM). In this new form, every symbol ends with a pulse, thus it doesn’t require any synchronization, and moreover it shows an improvement in terms of spectral efficiency and data rate. We present the expressions of spectral efficiency, power requirements, and the data rate improvement normalized to PPM, and we present also comparison results to MPPM modulation scheme.

The Extensible Authentication Protocol, or EAP, is an authentication framework used frequently in wireless networks and point-to-point connections. The Transport Layer Security (TLS) provides a secure communication layer, using asymmetric cryptography for key exchange, symmetric encryption for privacy and message authentication codes for message integrity. In this work we propose to replace the TLS handshake mechanism with the EAP authentication, which allows authentication to be easily integrated into multiple wireless network technologies using EAP-TLS.

The article presents a new approach in the field of automatic Physical Cell Id (PCI) assignment in LTE-advanced Self Organized Networks. The presented algorithm allows for multi-target optimization for different network deployment scenarios in order to minimize the number of PCI conflicts and confusions. Unlike some other competitive algorithms, the presented mechanism does not require any changes in the LTE specification, as the operation is based on standard information already available in the management system. The algorithm allows for specific limitations of the physical layer, e.g. setting the maximum number of co-existing PCIs in range in order to restrain interference. The presented algorithm is compared with other solutions through numerous simulations.

In this paper first the problem of secure minimum-cost multicast with network coding is studied, while the maximum end-to-end parameters, such as security, delay, and rate are assumed to be bounded in one multicast session. We present a decentralized algorithm that computes minimum-cost QoS flow subgraphs in network coded multicast networks. In next stage we generalize this idea to interference-limited dynamic networks where capacities are functions of the signal-to-noise-interference ratio (SINR). Since dynamic link capacities can be controlled by varying transmission powers, minimum-cost multicast must be achived by jointly optimizing network coding subgraphs with power control schemes. Simulation results shows this approach provides an efficient way for solving the optimization problem. The optimization numerical results show that using power control algorithm, higher success ratio is obtained, in comparison with previous algorithms.

Individual components of the communication system can be implemented in different environments on the stage of design and prototyping. Some of them are simulated in a high-level language environment, like matlab, and some are implemented in a target device, FPGA or signal processor, using evaluation boards. The verification of hardware implementation needs the communication interface sufficiently fast to transmit high amount of data. The Ethernet interface widely available on modern boards seems to be useful. The paper presents a set of modules, compiled as applications as well as implemented in FPGA, used to send data between PC and FPGA device over Ethernet omitting the TCP/IP protocol stack. The data are send and received by direct access to the Ethernet frames. Simple transmission protocol with acknowledgment was proposed to provide reliable data transmission.

The following paper describes some common aspects of stream data processing systems. The paper consists of two main parts – first showing the short description, tests results and conclusions of an implemented system – the AGKPStream, while the second part focuses on proposed solutions, created upon experiences gained during development of mentioned system, as well as knowledge collected during learning about some concepts of a StreamAPAS system. The first discussed issue is a tuple construction – basic data representation. It concerns tuple time model, tuple schema and a tuple decorator. Afterwards, the stream query and scheduling problems are described.

The growing importance of data warehousing [1-3] and the need to provide up-to-date information, changed procedures of data processing [4-8]. Classic data warehouses which are based on a traditional ETL process, proved to be ineffective and limited further development, due to the need of time-sharing of an access time between updates and analysis [9,10]. Introduction of the zero-latency data warehouse, solved the problem of data mining time limit, however it enforces the need to use larger computing power for processing updates and queries in the ETL process. The article presents two ETL systems for zero-latency data warehouses which implement the WINE-HYBRIS algorithm. The first ETL system processes tasks in CUDA and CPU architectures, while the second uses Cloud Computing. The purpose of the article is to describe advantages and disadvantages of each solution.

Molecular viewers allow visualization of spatial structures of proteins and other biological molecules. However, most of them are not able to read molecular structures stored in the PDBML format provided by the world-wide Protein Data Bank (PDB). In the paper, we present main features of the MViewer that we have designed and developed in order to support a man-protein structure interaction. The unique feature of the MViewer is the ability to open, read and visualize structures stored in all three formats (i.e. PDB, mmCIF, and PDBML) available from the PDB repository.

Protein structure alignment allows assessment of protein similarities and leads to the knowledge of the nature of proteins themselves. In this paper, we present a new version of the two-phase alignment algorithm for matching protein structures, called CASSERT. The algorithm can be used in scanning databases of protein structures while searching protein similarities. Effectiveness of the CASSERT was studied comparing its results to those returned by DALI algorithm. Performed tests confirm that the CASSERT algorithm exhibits high effectiveness in protein structure similarity searching and can be a useful tool in the identification of proteins and their functions.

The issue of quantum states’ transfer – in particular, for so-called Perfect State Transfer (PST) – in the networks represented by the spin chains seems to be one of the major concerns in quantum computing. Especially, in the context of future communication methods that can be used in broadly defined computer science. The paper presents a definition of Hamiltonian describing the dynamics of quantum data transfer in one-dimensional spin chain, which is able to transfer the state of unknown qudits. The main part of the paper is the discussion about possibility of entangled states’ perfect transfer, in particular, for the generalized Bell states for qudits. One of the sections also contains the results of numerical experiments for the transmission of quantum entangled state in a noisy quantum channel.

A generalized approach to Ping-Pong protocol analysis is introduced. The method is based on investigation of the density operator describing joint systems of communicating parties and an eavesdropper. The method is more versatile than approaches used so far as it permits on incorporation of different noise models in a unified way and make use of well grounded theory of quantum discrimination in estimation of eavesdropper’s information gain. As the proof of the method usefulness an example of its application to the analysis of the protocol execution over depolarizing and dephasing channels is given.

In the article we examine a model of TCP connection with Active Queue Management in an intermediate IP router. We model a system where CHOKe or gCHOKe are the AQM policy. We use the fluid flow approximation technique to model the interactions between the set of TCP/UDP flows and two variants of the CHOKe algoithms. The obtained results confirm the superiority of these algorithms over a standard RED algorithm.

In recent years energy market has changed. Consumers in many countries are free to buy energy from any of the available providers. This requires continuous reading from a huge number of energy meters to evaluate the amount of energy being bought from a particular provider. In this paper we present a fault-tolerant distributed stream processing system for continuous meter readings. The main goal of the system is to store the readings in a stream data warehouse for further analysis. We focus on modeling of the data stream intensity in order to estimate the size of buffers in a network of components composing the system. We present both the mathematical model of the intensity and the simulation results to prove the correctness of the theoretical analysis.

This paper presents studies of modeling operation of Web service containing Web and database servers. The first part of the paper describes the method to obtain parameters of real servers. Additionally, detailed description of experiments and the results are presented. In the second part of the paper the Web and database servers models are introduced. In both of the presented models it is taken into account that the server processors are multi-core. Presented models can be used to evaluate proposed Web systems via simulation experiments.

We investigate multiserver queueing systems with Poisson arrivals, identical servers and random capacity demands under assumption that demand’s service time is proportional to its capacity having an exponential distribution. For such systems statistical characteristics of the total demands’ volume are determined.

We consider a multi-server queueing system with session arrivals that operates in random environment. A session consists of a random number of customers. Sessions arrive to the system in Markovian arrival flow. Inter-arrival times of customers within each session are random. The service time of a customer has a phase type distribution. A numerically stable algorithm for calculation of the stationary distribution of system states is presented. The main performance measures are calculated.

In this paper, we analyze a tandem queueing system consisting of

R

multi-server stations without buffers. The input flow at the first station is a

MAP

(Markovian arrival process). The customers from this flow aim to be served at all

R

stations of the tandem. For any

r

-th station, besides transit customers proceeding from the (

r

 − 1)-th station, an additional

MAP

flow of new customers arrives at the

r

-th station directly, not entering the previous stations of the tandem. Customers from this flow aim to be served at the

r

-th station and all subsequent stations of the tandem. The service time of any customer arriving at the

r

-th station is exponentially distributed with the service rate depending of

r

. We present the recursive scheme for calculating the stationary distributions and the loss probabilities associated with the tandem.

Transient queue analysis is needed to model the influence of time-dependent flows on congestion in computer networks. It may be applied to the networks performance evaluation and the analysis of the transmissions quality of service. However, the exact queuing theory gives us only few practically useful results, concerning mainly M/M/1 and M/M/1/N queues. The article presents potentials of three approaches: Markovian queues solved numerically, the diffusion approximation, and fluid-flow approximation. We mention briefly a software we implemented to use these methods and summarise our experience with it.

The paper presents a new model of a multiservice queueing system with limited queue and state-dependent dynamic resource sharing of the server between individual classes of calls. The advantage of the proposed model is the possibility to evaluate the average parameters of queues for individual classes of calls. The proposed model can be taken as a basis for further research on multiservice queueing systems.

In this paper we study a scheduler for creating several virtual links on one physical link. The scheduler provides partial isolation of the performance between the virtual links in a sense that the volume of traffic offered to one virtual link may influence the performance of other virtual links, but only up to some extent. Namely, the virtual links have guaranteed boundaries of the performance characteristics, no matter what happens with other links. Contrary to schedulers with full performance isolation, the studied scheduler is partially work conserving – some heavily loaded virtual links may benefit from the light load of other virtual links. We give a description of the scheduler, compute boundaries of its performance characteristics and present the actual performance in several simulated scenarios.

This paper presents research on automatic speaker identification based on structural risk minimization and kernel functions. New approach, known as a Fuzzy Kernel Ho-Kashyap classifier FKHK, to speaker identification was applied. Instead of the most popular kernel functions like gaussian or polynomial, data dependent kernel matrix which may be interpreted in terms of linguistic values from the premises of if-then rules was applied. Classifier was tested on polish speech corpora ROBOT and obtained results were discussed.

The article presents selected, effective speech signal processing algorithms and their use in order to improve the automatic speech translation. Automatic speech translation uses natural language processing techniques implemented using algorithms of automatic speech recognition, speaker recognition, automatic text translation and text-to-speech synthesis. It is very possible to improve the process of automatic speech translation by using effective algorithms for automatic segmentation of speech signals based on speaker recognition and language recognition.

The paper discusses the possibility of application and modification of a sink movement strategy for multiple object tracking, with use of a wireless sensor network (WSN). Based on an extended Nagel-Schreckenberg 2D road traffic model various traffic conditions was obtained. Next, current methods of mobile sink control were used to research the energy consumption, its balance and efficiency. Finally, two modification was proposed to improve the WSN network utilisation. Simulation was performed on over 160 thousand nodes and compared against state-of-the-art approaches. The results show that the proposed modification to control strategies decreases energy consumption and improves uniform utilisation of nodes in WSN.

In this paper some modifications are proposed to optimize an algorithm of object tracking in wireless sensor network (WSN). The task under consideration is to control movement of a mobile sink, which has to reach a target in the shortest possible time. Utilization of the WSN resources is optimized by transferring only selected data readings (target locations) to the mobile sink. Simulations were performed to evaluate the proposed modifications against state-of-the-art methods. The obtained results show that the presented tracking algorithm allows for substantial reduction of data collection costs with no significant increase in the amount of time that it takes to catch the target.

Protection of computer systems from an unauthorized access to the classified information is a very essential issue. Security of IT systems can concern various aspects, such as software security, connected with ensuring its confidentiality, as well as preventing its modification. Thanks to the developed methods, it is possible to analyze the program code based on the disturbances of voltage supply, which occur during the execution of the program. Moreover, it also enables to recognize the numbers of bits changes on microcontroller data bus, as a result of realized instruction. In such context, it can constitute a potential threat for data processed by microcontroller program or embedded systems. The presented method is very similar to simple power analysis method, which is very effective in relation to cryptographic algorithms, whose execution in many cases depends on processed data. The results indicate that presented method is an effective and low-cost attack, due to its simplicity in many real applications. Moreover, the research results inspire to study carefully the ways and methodology for developing software and hardware, which should reduce the possibility of software reverse engineering.

The essential feature of modern IT systems, related to a device reliability, is their immunity to electromagnetic disturbances. The paper deals with the software-based techniques used for detecting disturbances, which can appear during the microcontroller work. The use of presented techniques allows the system to response appropriately to the threat.

The diversity and commonness of the sensors used for monitoring industrial processes and the widespread use of the digital data processing methods for the measurements are crucial issues related to the communication and data collection. The popular technical solutions for fast and reliable transmission of large packets of information cannot be directly applied in an environment where the risk of explosion appears. The paper shows the physical layer limitations for the transmission links with the potential danger of explosion of methane and coal dust that are characteristic for coal mines. Areas of mine-specific applications for data transmission were summarized and an example of safety parameters calculation for the RS485 communication standard was presented.

Data streaming is often used for video and sensor data delivery, nowadays gaining in popularity along with the development of mobile devices. In this paper we briefly describe a platform for automated composition of distributed data stream processing services. It decreases the complexity of composite service building process from the users point of view by introducing automation mainly in appropriate service selection and their communication protocols negotiation. This paper is focused on automated negotiation of communication protocols, which will be further used to transfer data among services. Data stream processing services are designed independently, often with many possible communication methods and not pointing directly to other services. With the use of the platform, they can be loosely coupled, forming a composite service od-demand. We present several approaches to communication protocol negotiation in a composition of data stream processing services and introduce planning-based approach. Finally, we discuss consequences of various approaches on an example composite service from image processing domain.

The rise of the Internet has increased the business transformation. Companies want to communicate with customers and partners in real-time. On the other side, Internet users demand speedy, well fitted access to actual information as well as to business applications. The paper focuses on user participation in the development of business information system (BIS). The paper includes the analysis of the empirical research results on user support software preferences.

This paper attempts to address the problem of the automatic customer segmentation by processing data collected in Social Customer Relationship Management (Social CRM) systems using Kohonen networks. Presented segmentation approach comprises classic loyalty-profitability link model that is explicit for CRM, and new social media components direct to Social CRM. The result of presented approach is an analysis tool with data visualization for managers which significantly improves the process of customer segmentation. Presented research is supported by implementation of proposed approach by which experiments were conducted. Additionally, the experimental results showed that proposed method performed very close to k-means algorithm which indicate the correctness of the proposed approach.

The paper concerns Web server log file analysis to discover knowledge useful for online retailers. Data for one month of the online bookstore operation was analyzed with respect to the probability of making a purchase by e-customers. Key states and characteristics of user sessions were distinguished and their relations to the session state connected with purchase confirmation were analyzed. Results allow identification of factors increasing the probability of making a purchase in a given Web store and thus, determination of user sessions which are more valuable in terms of e-business profitability. Such results may be then applied in practice, e.g. in a method for personalized or prioritized service in the Web server system.

Indexing is a key element of optimization of relational database systems (RDBMS). Commercial tools supporting index selection (e.g. SQL Access Advisor, Toad, SQL Server Database Tuning Advisor, DB2 Advisor) are based on the methods dedicated to individual queries. This paper presents a new approach to tables indexing for the SQL queries group that take into account the size of the indexes and their creation time. Examples illustrate that the use of the group concept reduces the query execution time by 44,% compared to classical methods.

In this paper an auction based scheduling algorithm with the options of three different pricing policies is presented and investigated. The Quality of Service as assuring bandwidth on a proper level during transmission of resources is analyzed. Presented experiments were performed in a real-life web service and three performance indexes were evaluated (service income, mean value of

RFM

and number of offers with lower account price than offered price).