Mirjana D. Stojanovic

End-to-end quality of service specification and mapping: The third party approach

This article addresses an open issue of end-to-end service specification and mapping in next generation networks. A centralized approach has been considered, via the third party agent that manages negotiation process in a group of domains. We suggest a general structure of the service specification form, which contains technical parameters related with a particular service request. Relying on such general form, we further propose and evaluate an efficient algorithm for service class selection. The algorithm selects the most appropriate class for each domain by determining the closest conformance between the required and offered service level. We also present a numerical example that demonstrates operating of the algorithm. Performance evaluation has been performed on the prototype implementation. Results of the analysis have pointed out the following important advantages of our approach: fairness in resource consumption, flexibility in class selection according to specific management policy and adaptability to different quality of service models.

Influence of Soil Type and Physical–Chemical Properties on Uranium Sorption and Bioavailability

This work was undertaken to study the influence of soil type and its physical and chemical properties on uranium sorption and bioavailability, in order to reduce the uncertainty associated with this parameter in risk assessment models and safe food production. The tests were conducted on three types of Serbian soils: alluvium, chernozem, and gajnjaca, from which 67 samples were taken. Dominant factors of uranium mobilisation: the specific content of total/available form of uranium and phosphorus, the degree of acidity (pHKCl), and humus content and their correlation, were analysed. Content of available uranium form, according to the type of soil decreases in the following order: gajnjaca > alluvium > chernozem. It was found the medium correlation between pH values and available content of uranium in chernozem and gajnjaca, statistically significant at the level of significance of 99% and the alluvium at the level of significance of 95%. Correlation coefficients in all cases were negative, indicating that the reduction in pH increases the mobility of uranium and thus its availability for the adoption of the plants. Soil pH was the only dominant factor that significantly controlled the uranium value with no further significant contribution of other soil parameters.

A simulation analysis of statistical multiplexing in frame relay and ATM interworking

This paper presents a simulation analysis of statistical multiplexing of virtual connections at the ATM access node. We analyze the bandwidth assignment implications assuming various service interfaces (FR and ATM). The important conclusion that we draw from the simulation results is that the allocation of bandwidth in the multiplexer is strongly dependent on the type of service interface.

SLA-controlled interconnection charging in next generation networks

Next generation network (NGN) should facilitate a single party to establish quality of service (QoS) enabled path between the two IP providers mutually interconnected by one or more transit providers. For that purpose, an end-to-end service level agreement (SLA) should be negotiated and maintained. In this article, we propose interconnection charging, which is controlled by the end-to-end SLA. Relationships between the required, offered, and actually achieved inter-provider QoS are quantified through the degrees of offering and provisioning, at both end-to-end and per-domain levels. Nominal retail price offered to end users and interconnection costs related with particular SLA are then corrected if needed, depending on the offered and provisioned QoS levels. We further propose five policies for interconnection charging and compare them under different QoS provisioning scenarios. Results of the analysis indicate that a properly selected SLA-controlled interconnection charging policy should encourage providers: (1) to offer services with different QoS levels; (2) to offer service that perfectly or most approximately matches the required QoS and (3) to achieve the contracted QoS level.

Analysis of SCADA system vulnerabilities to DDoS attacks

Several factors have contributed to the escalation of risks specific to novel control systems, including the network architecture, adoption of standardized technologies with known vulnerabilities and connectivity of control systems to other networks. This paper considers SCADA (Supervisory Control And Data Acquisition) system vulnerabilities as well as securing the infrastructure of power utility information-telecommunication systems. We first present a concept of SCADA architecture in the hydropower plants. The simulation model assumes Distributed Denial of Service (DDoS) attack to SCADA system. A comprehensive simulation points to SCADA performance deterioration under DDoS attack. Possible security solutions have also been discussed.

An efficient QoS mapping algorithm in multi-provider networks

This paper addresses the problem of service specification and mapping across providers, supposing centralized approach, via the third party agent that manages negotiation process in a group of domains. A general structure of the service specification form is suggested. It contains technical parameters related with a particular service request. Based on such general form, we further propose, implement and evaluate an efficient algorithm for service class selection. The algorithm selects the most appropriate class for each domain by determining the closest conformance between the required and offered service level.

Quality of Service Negotiation in Next Generation Networks

This paper addresses different aspects of quality of service (QoS) negotiation in next generation networks. The differentiated services (DiffServ) framework is assumed in a multi-domain network core, while access networks may implement other QoS models. QoS negotiation results in service level agreement (SLA), i.e., a contract between the provider and the user, which defines technical, financial and legal aspects related with particular service. Solutions for SLA structure and format are discussed, with respect to mapping algorithms on the network-to-network interface. Considering conditions of contract violation, different traffic conditioning policies have been compared by computer simulation. We further provide a brief overview of the recently proposed next steps in signaling (NSIS) framework. The paper also addresses possibilities to achieve efficient usage based pricing in accordance with negotiated technical parameters from the SLA. Finally, we briefly present the object-oriented design and implementation of the application SLA Manager (SLAM), which is intended for QoS negotiation in DiffServ IP network.

SLAM: an Object-Oriented Application for IP Quality of Service Negotiation

In the first part of this paper, we propose a formal service level specification in IP-based networks with differentiated services. The specification encompasses technical part of the service level agreement between the Internet service provider (ISP) and the user (either end user or another ISP). In the second part of the paper, design of the application SLAM (service level agreement manager) has been presented, relying on the proposed formal specification. SLAM has been developed for Windows environment, using object oriented design and C++ programming language. SLAM consists of the following three agents: the first agent is user-oriented and is responsible for service negotiating; the second agent simulates functions of the network resource manager, while the third agent is intended to the network administrator and provides an access to all negotiated agreements.

Approaches to Quality of Experience management in the future Internet

Previously dominating research on the Internet Quality of Service (QoS), focused on network performance, has now been shifted towards the customer experience. This paper addresses Quality of Experience (QoE) management issues in the future Internet. We provide a brief overview of QoE metrics and assessment methodologies, and discuss potential relationships between the QoE and network performance parameters. Further, we discuss open technical issues in achieving the inter-provider QoS, including large scale end-to-end measurements. User-centric management assumes a layered approach that includes network infrastructure, network performance, and the user awareness. Business opportunities for service providers in the context of QoE management are also emphasized. We conclude the paper with a list of the most important directions for further research in the area.

Load balance routing for interconnected next generation networks performances improvement

In this paper, results of extensive research concerning synergy of dynamic routing and interconnection charging methods are presented. The impact of various dynamic traffic routing methods on different performances of interconnected telecommunications network with the application of bill-and-keep interconnection charging is analysed. For the purpose of our research, we developed the software for Routing and Interconnection Simulation — RIS. Analysing obtained results we noticed that with application of some routing methods, there are several links completely unused. We introduce the new load balance routing method in order to improve some performances of interconnected next generation networks — NGN.