Udo R. Krieger

Udo R. Krieger

About

135
Publications
7,468
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
903
Citations

Publications

Publications (135)
Chapter
We consider a scale-free model of the Web network that is evolving by preferential attachment schemes and derive an explicit formula of its PageRank vector. Its \(i^{th}\) element indicates the probability that a surfer resides at a related Web page i in a stationary regime of an associated random walk. Considering the growth of a directed Web grap...
Book
Full-text available
This book constitutes the refereed proceedings of the 21st International Conference on Innovations for Community Services, I4CS 2021, held in Bamberg, Germany, in May 2021 as a hybrid event. The 14 full papers and 2 short papers presented in this volume were carefully reviewed and selected from 43 submissions. One short invited paper is also includ...
Chapter
We consider a fog computing approach with function virtualization in an IoT scenario that uses an SDN/NFV protocol stack and multipath communication between its clients and servers at the transport and session layers. We analyze the reliability of the associated redundant transport system comprising two logical channels that are susceptible to rand...
Chapter
Full-text available
The paper is devoted to the statistical analysis of the end-to-end (E2E) delay of packet transfers between source and destination nodes in a peer-to-peer (P2P) overlay network. We focus on the identification of the E2E delay and the longest per-hop delay distributions and the stochastic dependence of the associated random process. The E2E delay is...
Chapter
We consider the multipath communication between a client and a server that is established at the transport and session layers of an SDN/NFV protocol stack in a fog computing scenario. We analyze the reliability function of an associated redundant transport system comprising two logical channels that are susceptible to failures. The failure processe...
Article
Full-text available
In recent years we have realized a rapid development regarding the Internet of Things (IoT). Its goal is to interconnect all possible devices to the Internet and to enhance these physical objects by new functionalities. In this way a user's life standard shall be improved. Regarding the application of Internet of Things concepts, there are some com...
Chapter
We consider a permissioned blockchain and analyze the dissemination and commitment processes of blocks among its corresponding miner nodes in the underlying peer-to-peer network. We propose a Markovian non-purging (n, k) fork-join queueing model to analyze the delay performance of the synchronization process among these miner nodes that apply a vot...
Chapter
In the field of computer systems the world has entered an era of Internet of Things, which consists in connecting all possible devices to the Internet in order to provide them with new functionalities and in this way to improve the user life standard. There are lot of systems which required the possibility for monitoring their condition. One of the...
Conference Paper
We consider the transmission of protocol data units in an LTE eNodeB in downlink direction and focus on the radio link control (RLC) and hybrid Automatic-Repeat-Request functionality at layer 2 of the transmission system. We model the associated window flow control of RLC frames in terms of an open queueing network with two stations and describe RL...
Article
First we discuss the numerical aspects of a computational approach for the performance evaluation of advanced telecommunication networks by finite continuous-time Markov chains. Then we illustrate by two examples the benefits and difficulties of direct and iterative methods that are applied for the solution of the singular systems arising in this f...
Conference Paper
We analyze the cluster structure in large networks by means of clusters of exceedances regarding the influence characteristics of nodes. As the latter characteristics we use PageRank and the Max-Linear model and compare their distributions and dependence structure. Due to the heaviness of tail and dependence of PageRank and Max-Linear model observa...
Conference Paper
Fog computing constitutes currently a challenging effort to establish the concepts and services of cloud computing at the edge of converging wireless networks and wired high-speed backbones. We discuss the concepts of our fog computing platform HCL-BaFog. It is built on top of Hypriot Cluster Lab (HCL) which has been developed by the Hypriot Pirate...
Conference Paper
Full-text available
We investigate the performance of a LRU cache replacement policy. Regarding the hit and miss ratios of Zipf-distributed frequencies of object requests in a cascade of LRU caches, new explicit, computationally tractable formulae are derived.
Conference Paper
We consider the efficiency of dynamic resource pooling and allocation in a cloud computing system offering infrastructure-as-a-service (IaaS). We assume that the demand for service computing by virtual machines (VMs) follows a Poisson load pattern and that the response times of the provided computing services can be classified into several service...
Conference Paper
The paper is devoted to caching of popular multimedia and Web contents in Internet. We study the Cluster Caching Rule (CCR) recently proposed by the authors. It is based on the idea to store only popular contents arising in clusters of related popularity processes. Such clusters defined as consecutive exceedances of popularity indices over a high t...
Conference Paper
Today, most mobile devices are equipped with multiple wireless network interfaces, but are constrained to use only one network at the same time. In this paper, we show that using multiple access networks simultaneously can improve user-perceived QoS and cost-effectiveness. We present a system architecture that exploits the adaptive forwarding plane...
Conference Paper
Current IP-based networks are unable to fully exploit the capabilities of the increasing number of multihomed mobile terminals. We argue that Content-Centric Networking (CCN), a novel networking architecture based on named information objects, can fill the gap. In this paper, we elicit requirements for CCN packet forwarding on multihomed mobile ter...
Conference Paper
Full-text available
Modeling the overlay graph of peer-to-peer (P2P) data dissemination is inherently difficult due to the high dynamics of the peer behavior and the high degree of connectivity if we regard a mesh-pull architecture. We present a solution of the latter issue using the mathematical tools of Kronecker graphs.We are able to capture accurately the static s...
Chapter
Video streaming currently dominates global Internet traffic and will be of even increasing importance in the future. In this paper we assess the impact of the underlying transport protocol on the user perceived quality for video streaming using YouTube as example. In particular, we investigate whether UDP or TCP fits better for Video-on-Demand deli...
Chapter
Full-text available
Packet video and voice are the dominant traffic sources in today’s Internet. Numerous studies have dealt with the influence of packet loss on video and voice quality. We elaborate on the root causes of packet loss in the Internet and show by statistical methods how that affects the quality of transmitted real-time data. We evaluate the mean number...
Article
We present a performance analysis concerning the application of Raptor codes as forward error correction mechanism at the application layer of Android devices. At first, a short overview on practical aspects of the implementation of Raptor coding is given. Subsequently, methods to increase the coding performance on ARM processors are presented and...
Conference Paper
This study investigates two innovative content delivery proposals of next generation Internet, namely Libswift and CCN. We present results of a measurement campaign performed on a realistic network testbed to evaluate and compare their performance in relation to reference measurements obtained by the traditional client/server approach. The results...
Conference Paper
The success of peer-to-peer live video streaming in wireline networks has inspired the development of mobile peer-to-peer streaming technologies. However, the traditional peer-to-peer live streaming techniques have been found to perform sub-optimal in wireless networks. Furthermore, the increasing energy consumption in wireless networks due to inef...
Conference Paper
Full-text available
Mobile data consumption establishes as a massively growing market, because the proliferation of powerful smartphones and tablets on mobile networks is a major traffic generator nowadays. In order to guarantee an acceptable quality of experience to the end user, current studies try to improve data transmissions on air interfaces. However, the bottle...
Conference Paper
Full-text available
The proliferation of smart devices for mobile networks is a major traffic generator nowadays. These devices provide the ability to receive media content in nearly every situation. Despite that video streaming in high quality is getting more and more popular in mobile scenarios, the performance and bottlenecks of mobile applications over wireless ne...
Conference Paper
The amount of mobile video streaming traffic is rapidly growing and a potential candidate to reduce the load on the content delivery infrastructure is given by the peer-to-peer (P2P) paradigm. One might argue about the adequacy of P2P in this mobile context, yet, it has already become reality. Popular P2P streaming networks like SopCast or TVU netw...
Conference Paper
Full-text available
Applying advanced statistical techniques, we characterize the peculiarities of a locally observed peer population in a popular P2P overlay network. The latter is derived from a mesh-pull architecture. Using flow data collected at a single peer, we show how Pareto and Generalized Pareto models can be applied to classify the local behavior of the pop...
Conference Paper
The paper contributes to the development of a framework concerning the teletraffic modeling and analysis of peer-to-peer systems that are based on a mesh-pull architecture. We look at the packet transmission processes induced by a swarm of peers disseminating multimedia objects. We provide a survey on some statistical techniques that are used to ch...
Conference Paper
In this paper we present the first distributed measurement campaign conducted by the P2P framework Seattle. Seattle is a distributed PlanetLab like network testbed that easily enables everyone to participate. The contributions of the paper are the following: First, we conduct a thorough analysis of the prevalent conditions in the Seattle network an...
Conference Paper
Full-text available
In this paper we present the architecture of the first mobile P2P streaming prototype for the operating system Android. At first, we discuss the application of P2P streaming in the scenario of mobile networking. Then, the system and software architecture of our prototypical implementation is elaborated. In addition, an initial field test to evaluat...
Article
Full-text available
Motivated by the current integration of radio access net-works and the IP-based high-speed data communication in core networks, we have developed a new quality-of-service management concept for mobile environments. Following the IntServ service model, it provides resource reservation, control and signaling mechanisms and is able to interwork with R...
Conference Paper
The specification and development of models for Internet traffic is mainly conducted by measurement-driven performance modeling based upon statistical analysis. Yet, this type of analysis can be a challenging task, due to the complexity and especially, with large sample sizes, the sheer quantity of the data. For this reason, preliminary data examin...
Conference Paper
Full-text available
In this paper, we present a first analysis of the application of Raptor codes in the domain of P2P streaming. With the help of fountain codes, such as Raptor codes, it is possible to completely omit content reconciliation in P2P networks. Hereby, the scheduling complexity of the data dissemination is greatly reduced. The contributions of the paper...
Article
Polling systems provide performance evaluation criteria for a variety of demand-based, multiple-access schemes in computer and communication systems [1]. For studying this systems it is necessary to find their important characteristics. One of the important characteristics of these systems is the k-busy period [2]. In [3] it is showed that analytic...
Chapter
Full-text available
In Web information retrieval stochastic link analysis provides important supplementary means to generate a ranking of searched objects. Considering a hierarchical algebraic description of a Web graph with host-oriented clustering of pages or a role-oriented perspective, we propose an efficient computation of the stationary distribution of the under...
Article
Full-text available
A non-Markovian feedback single-server retrial queue with collisions and general retrial times is investigated. A necessary and sufficient condition for the system to be stable is studied. Using the supplementary variable technique, the joint distribution of the server state and the orbit length under steady-state is obtained. Some interesting and...
Chapter
We study peer-to-peer packet traffic arising from passive VoIP and video measurements that are generated by Skype and IPTV clients. We provide a common methodology for the statistical characterization of the packet flows, discuss the user’s satisfaction and load estimation. Two main ideas are used in our analysis. Due to the dependence of the data...
Conference Paper
The extensive growth of peer-to-peer video applications (P2PTV) indicates the evolutionary path towards the next generation of networking. To enhance the quality of experience for P2PTV users, new P2P video traf?c models are required. These models are often developed by measurement-driven performance modeling based upon statistical analysis. Howeve...
Conference Paper
We consider measurements that are arising from a next generation network and present advanced mathematical techniques to cope with the analysis and modeling of the gathered data. These statistical techniques are required to study important performance indices of new real-time services in a multimedia Internet such as the demanded bandwidth or delay...
Article
Full-text available
Mobile peer-to-peer (P2P) traffic is rapidly growing, but present P2P applications are not specifically designed to operate under mobile conditions. To assess the performance of the prevalent file sharing application BitTorrent in a mobile WiMAX network, we performed a measurement and analysis campaign. In this study, we use the obtained measuremen...
Article
The traffic characterization of adaptive real-time applications provides a challenging engineering task of the current Internet. Here the arrival and packet length processes arising from a unidirectional VoIP flow of Skype packets are investigated by statistical means. The mean traffic load offered by the packet flow to a virtual link of limited ca...
Conference Paper
Currently, the rapid development of new multimedia services including VoIP, video streaming and video on demand as well as IPTV and the integration of triple play into the service portfolios of ISPs and network operators indicate an evolutionary path towards next generation networking. Peer-topeer (P2P) overlay networks are used with growing intens...
Conference Paper
Full-text available
In this study we examine statistical properties of traffic generated by the popular P2P IPTV application SopCast. The analysis aims at a better understanding of the mechanisms used by such applications and their impact on the network. Since the most popular P2P IPTV applications use proprietary unpublished protocols, we look directly at the generat...
Conference Paper
Full-text available
We present a comprehensive traffic measurement and analysis concept to cope with the rapid deployment of peer-to-peer multimedia applications and their overlay structures. It integrates four orthogonal dimensions: traffic measurements at the packet layer, data extraction, flow analysis and inspection of peer-to-peer overlays based on a hierarchical...
Article
The analysis of QoE and QoS of adaptive real-time applications provides a challenging task in the current Internet. Here, we study major characteristics of Skype user satisfaction. For this purpose we estimate the loss and delivery time variation by inter-arrival times (IAT) between packets and packet lengths (PL) of an individual unidirectional fl...
Conference Paper
Full-text available
This paper introduces the CPP/M/c model with working vacations to describe queueing phenomena that arise in an advanced computing environment of virtualized servers operated by the infrastructure owners. In the proposed queue the inter-arrival times of jobs requesting servers follow a Generalized Exponential distribution. To model a maintenance act...
Article
Full-text available
In the current Internet the performance of service delivery crucially depends on the proper and efficient operation of Web servers. It is determined by their software architecture and characterized by the applied processing model. Here we consider the Unix software architecture of an Apache Web server with its non-threaded multi-processing module P...
Conference Paper
At present, Web portals offering streaming of stored video contents or live TV channels have become a rapidly emerging new Internet service. We investigate the traffic characteristics, performance and perceived quality of available IPTV services which use peer-to-peer (P2P) overlay networks, called P2PTV. We analyze gathered traces of a comprehensi...
Article
Full-text available
We consider an estimate of the renewal function (rf) H(t) using a limited number of independent observations of the interarrival times for an unknown interarrival-time distribution (itd). The nonparametric estimate is derived from the rf-representation as a series of distribution functions (dfs) of consecutive arrival times using a finite summation...
Article
In teletraffic engineering, the effective design of wireless networks providing voice and data services at hot spots is of great practical importance. This paper presents a model of such networks in terms of a BMAP/PH/N retrial queue. Due to the batch occurrence and high correlation of the traffic, it is decisive to choose the correct Batch Markovi...
Article
Feedback queues play an important role in real-life service systems, where customers may require repeated services. In this paper, we consider a feedback queue with batch Markovian arrivals and phase type services. We further assume that both the arrival process and service times are influenced by an external finite state Markovian environment. The...
Article
Full-text available
p align="LEFT">Queueing systems with feedback are well suited for the description of message transmission and manufacturing processes where a repeated service is required. In the present paper we investigate a rather general single server queue with a Markovian Arrival Process (MAP), Phase-type (PH) service-time distribution, a finite buffer and fe...
Article
Using an object-oriented simulation model of a basic client–server scenario in a wireless ATM network, we study the impact of handover and error-control protocols on the performance of high-speed data communication by the ABR service class. We present performance results of the ABR flow-control protocols ERICA and ERICA+ and discuss some implicatio...
Conference Paper
We sketch a QoS framework for adaptive mobile multi-media environments that integrates mobility- and quality-of-service management with new connection admission control (CAC) schemes. Refering to measurement-based CAC procedures applied in mobile access networks, we discuss their extension to adaptive mobile applications and describe the integratio...
Article
Full-text available
This paper is devoted to the estimation of heavy-tailed probability density functions (p.d.f.s), their mixtures and high quantiles. We discuss the relevance of this issue in teletraffic engineering and propose a new combined estimation technique for such p.d.f.s. The “tail” of the p.d.f. is estimated by a parametric tail model and its “body” by a n...
Article
Full-text available
The fuzzy explicit rate marking (FERM) is a rate-based algorithm for the ow control and congestion avoidance of ABR connections in an ATM network. In this paper we describe a promising adaptation of FERM and its use in a wireless ATM (WATM) network simulation scenario.
Article
Using an object-oriented simulation model of a basic client-server scenario in a wireless ATM network, we evaluate the performance of different handover protocols. They are combined with different error-control protocols to support high-speed data communication by the ABR service class. We present simulation results of the ABR flow-control protocol...
Article
Considering the realistic teletraffic analysis in advanced telecommunication networks, the estimation of basic characteristics of arrival processes by empirical data is an important subject of current research. Using independent observations of the interarrival times between events and the mean numbers of events in intervals of fixed length, we pro...
Article
this document, several methods of AC for stream traffic based on declared parameters and using bufferless multiplexing are proposed

Projects

Projects (2)