Bozydar Dubalski

Assessing Measurements of QoS for Global Cloud Computing Services

Many global distributed cloud computing applications and services running over the Internet, between globally dispersed clients and servers, will require certain levels of Quality of Service (QoS) in order to deliver and give a sufficiently smooth user experience. This would be essential for real-time streaming multimedia applications like online gaming and watching movies on a pay as you use basis hosted in a cloud computing environment. However, guaranteeing or even predicting QoS in global and diverse networks supporting complex hosting of application services is a very challenging issue that needs a stepwise refinement approach to be solved as the technology of cloud computing matures. In this paper, we investigate if latency in terms of simple Ping measurements can be used as an indicator for other QoS parameters such as jitter and throughput. The experiments were carried out on a global scale, between servers placed in universities in Denmark, Poland, Brazil and Malaysia. The results show some correlation between latency and throughput, and between latency and jitter, even though the results are not completely consistent. As a side result, we were able to monitor the changes in QoS parameters during a number of 24-hour periods. This is also a first step towards defining QoS parameters to be included in Service Level Agreements for cloud computing in the foreseeable future.

Energy Greedy Protocol Suite for Smart Grid Communication Systems Based on Short Range Devices

In this paper, we present new communication protocol, named energy greedy quasi-flooding protocol. This protocol is independent from a communication media types and is mainly intended for PLC, UHF wireless and even IrDA transmission techniques. Presented solutions can be applied to EMSs based on the inexpensive SRDs, they are also suite for smart grid technologies based on hybrid networks e. g. PLC together with the wireless.

Using latency as a QoS indicator for global cloud computing services

Many globally distributed cloud computing (CC) applications and services running over the Internet, between globally dispersed clients and servers, will require certain levels of QoS in order to deliver and give a sufficiently smooth user experience. This would be essential for real‐time streaming multimedia applications such as online gaming and watching movies on a pay as you use basis hosted in a CC environment. However, guaranteeing or even predicting QoS in global and diverse networks that are supporting complex hosting of application services is a very challenging issue that needs a stepwise refinement approach to be solved as the technology of CC matures. In this paper, we investigate if latency in terms of simple ping measurements can be used as an indicator for other QoS parameters such as jitter and throughput. The experiments were carried out on a global scale, between servers placed in universities in Denmark, Poland, Brazil, and Malaysia. The results show the correlation between latency and throughput, and between latency and jitter, even though the results are not completely consistent. As a side result, we were able to monitor the changes in QoS parameters during a number of 24‐hour periods. This is also a first step toward defining QoS parameters to be included in service level agreements for CC at the global scale in the foreseeable future. Concurrency and Computation: Practice and Experience, 2013.© 2013 Wiley Periodicals, Inc.

Analysis of Degree 5 Chordal Rings for Network Topologies

This paper presents an analysis of degree 5 chordal rings, from a network topology point of view. The chordal rings are mainly evaluated with respect to average distance and diameter. We derive approximation expressions for the related ideal graphs, and show that these matches the real chordal rings fairly well. Moreover, the results are compared to that of a reference graph which presents a lower bound for average distance and diameter among all regular graphs of degree 5. It turns out that this reference graph has significantly lower distances than the degree 5 chordal rings. Based on that, we suggest that future research could deal with either finding degree 5 topologies with average distance and diameter closer to these of the reference graph, or to develop more realistic bounds than those presented by these reference graphs.

Evaluation of modified degree 5 chordal rings for network topologies

In this paper an analysis of modified degree 5 chordal rings is presented. First modified graphs and reference graphs (ideal and optimal) have been defined, and it is shown that the reference graphs are useful for estimation of average path length and diameter in both original and modified graphs. Then the comparison of basic graph parameters, diameter and average path length, is given for original and modified graphs. Our finding shows that the modified graphs contain shorter distances than the original graphs, and thus can be good candidates for network topologies.

Describing N2R Properties Using Ideal Graphs

N2R structures are a subset of Generalized Petersen Graphs and a potentially good option to be used for implementing degree three networks. The previous works on these structures verify that N2R are better than other degree three regular topologies such as Double Rings or Honeycomb in terms of path distances. The cost of this good performance is a more complex and non-planar interconnection configuration; It is complex to find analytical models to be used, for example for describing topological parameters. This paper proposes and verifies the possibility of approximating real N2R graphs to optimal and ideal graphs, which are much easier to model, obtaining fairly accurate results. A main result of the paper is a simple formula for approximating average distance and diameter given the number of nodes in a N2R graph.

Comparison of Modified Degree 6 Chordal Rings

In this paper we introduce a number of variants of modified degree 6 chordal rings, and we evaluate and compare their transmission properties in terms of average distance and diameter.We present theoretical models for calculating the distances, using optimal and ideal graphs, which are also shown to provide fairly good estimates. When comparing the distances, it turns out that the new suggestions for modification of the chordal rings results in lower distances, making them potentially interesting for use in communication networks. In the end of the paper we suggest directions for future research, in particular to investigate to what extend the topologies are suitable to implement.

A Comparison of Network Planning Strategies

In this paper we explore different strategies for planning and expanding networks based on chordal rings. For chordal rings of different sizes (10,30 and 50 nodes), and with two different traffic distributions (random and uniform) we study how average distance and diameter change as the chords are added. In the first strategy chords are added one by one, so that the distances are reduced in each step. In the second strategy a constraint is added, so that nodes can only have degree 3 or 4. In the last strategy chords are added gradually so that they fit into an initially calculated best, regular chordal ring of degree 3 or 4. The first strategy results in the best distances. The constrained node degrees comes next, whereas the regular rings have slightly larger distances through all steps.

Errors Nature in Indoors Low Power 433 MHz Wireless Network

In this paper, we present some results of long-term measurement in the 433 MHz, wireless telemetric network dedicated to watt-hour meter reading. The RSSI of received packets was measured by the sink. The sink was equipped with a half wave, 4 dBi antenna. Received and recorded data enabled us to make analysis of PER versus RSSI from all nodes within range of the sink, simultaneously. With knowledge of how many packets sink expected to receive, during the query and how long frames were, we propose the designation of the value of FER estimator. Lack of relationship between FER and frame length prompted us to investigate errors at bits level. Both the sink and other nodes were equipped with CC1101 low power RF transceiver. The paper concludes with the areas of the results application.

A hybrid Genetic and Simulated Annealing Algorithm for Chordal Ring implementation in large-scale networks

This paper presents a hybrid Genetic and Simulated Annealing algorithm to implement Chordal Ring structures in optical backbone networks. In recent years, topologies based on regular graph structures gained a lot of interest due to their good communication properties for physical topology of the networks. There have been many use of evolutionary algorithms to solve the problems which are in combinatory complexity nature, and extremely hard to solve by exact approaches. Both Genetic and Simulated annealing algorithms are similar in using controlled stochastic method to search the solution. The paper combines the algorithms in order to analyze the impact of implementation performance.