Next generation networks (NGNs) must integrate the services of current circuit-switched telephone networks and packet-switched data networks. This convergence towards a unified communication infrastructure necessitates from the high capital expenditures (CAPEX) and operational expenditures (OPEX) due to the coexistence of separate networks for voice and data. In the end, NGNs must offer the same services as these legacy networks and, therefore, they must provide a low-cost packet-switched solution with real-time transport capabilities for telephony and multimedia applications. In addition, NGNs must be fault-tolerant to guarantee user satisfaction and to support business-critical processes also in case of network failures. A key technology for the operation of NGNs is the Internet Protocol (IP) which evolved to a common and well accepted standard for networking in the Internet during the last 25 years. There are two basically different approaches to achieve QoS in IP networks. With capacity overprovisioning (CO), an IP network is equipped with sufficient bandwidth such that network congestion becomes very unlikely and QoS is maintained most of the time. The second option to achieve QoS in IP networks is admission control (AC). AC represents a network-inherent intelligence that admits real-time traffic flows to a single link or an entire network only if enough resources are available such that the requirements on packet loss and delay can be met. Otherwise, the request of a new flow is blocked. This work focuses on resource management and control mechanisms for NGNs, in particular on AC and associated bandwidth allocation methods. The first contribution consists of a new link-oriented AC method called experience-based admission control (EBAC) which is a hybrid approach dealing with the problems inherent to conventional AC mechanisms like parameter-based or measurement-based AC (PBAC/MBAC). PBAC provides good QoS but suffers from poor resource utilization and, vice versa, MBAC uses resources efficiently but is susceptible to QoS violations. Hence, EBAC aims at increasing the resource efficiency while maintaining the QoS which increases the revenues of ISPs and postpones their CAPEX for infrastructure upgrades. To show the advantages of EBAC, we first review today’s AC approaches and then develop the concept of EBAC. EBAC is a simple mechanism that safely overbooks the capacity of a single link to increase its resource utilization. We evaluate the performance of EBAC by its simulation under various traffic conditions. The second contribution concerns dynamic resource allocation in transport networks which implement a specific network admission control (NAC) architecture. In general, the performance of different NAC systems may be evaluated by conventional methods such as call blocking analysis which has often been applied in the context of multi-service asynchronous transfer mode (ATM) networks. However, to yield more practical results than abstract blocking probabilities, we propose a new method to compare different AC approaches by their respective bandwidth requirements. To present our new method for comparing different AC systems, we first give an overview of network resource management (NRM) in general. Then we present the concept of adaptive bandwidth allocation (ABA) in capacity tunnels and illustrate the analytical performance evaluation framework to compare different AC systems by their capacity requirements. Different network characteristics influence the performance of ABA. Therefore, the impact of various traffic demand models and tunnel implementations, and the influence of resilience requirements is investigated. In conclusion, the resources in NGNs must be exclusively dedicated to admitted traffic to guarantee QoS. For that purpose, robust and efficient concepts for NRM are required to control the requested bandwidth with regard to the available transmission capacity. Sophisticated AC will be a key function for NRM in NGNs and, therefore, efficient resource management concepts like experience-based admission control and adaptive bandwidth allocation for admission-controlled capacity tunnels, as presented in this work are appealing for NGN solutions. / In meiner Dissertation zum Thema “Performance Evaluation of Efficient Resource Management Concepts for Next Generation IP Networks” werden im Wesentlichen zwei miteinander verwobene Konzepte zur effizienten Nutzung von Übertragungsressourcen in zukünftigen IP Netzen untersucht. Das Management solcher Ressourcen ist zur Unterstützung qualitativ hochwertiger Netzdiensten (z.B. IP Telephonie, IP TV, etc.) in Zukunft unabdingbar. Gegenwärtig werden diese Dienste durch den Einsatz hoher Übertragungskapazitäten (engl. capacity overprovisioning) in den IP Breitbandnetzen ermöglicht. Um in Spitzenlastzeiten die Qualität der Dienste aufrecht zu erhalten, sind die Bandbreiten derart hoch angesetzt, dass unter normalen Umständen die Ressourcen nur sehr schwach ausgelastet sind (im Bereich zwischen 10 und 30 Prozent). Diese Überdimensionierungslösung ist einfach zu realisieren aber auch sehr kostenintensiv, ineffizient und vor allem nicht (zukunfts-)sicher, da bei ständig steigendem Bandbreitenbedarf, die Netzkapazitäten häufig angepasst werden müssen. Eine Effizienzsteigerung bei der Ressourcennutzung in heutigen Kommunikationsnetzen ist daher ein wichtiges Kriterium für die Wirtschaftlichkeit zukünftiger IP Netze. Erreicht werden kann dies mit den Mitteln der Netzzugangskontrolle (engl. admission control, kurz AC), welche bereits in verschiedenen Formen entwickelt, untersucht und teilweise auch in heutigen IP Netzen realisiert ist. Die AC stellt eine vergleichsweise komplexe Lösung zur Aufrechterhaltung der Dienstgüte in IP Netzen dar. Daher sind einfache und effiziente Mechanismen/Automatismen zur Durchführung der AC gefordert, um deren Einsatz an Stelle der Überdimensionierung zu rechtfertigen. Den zuvor genannten Forderungen nach effizienter Ressourcennutzung entsprechend stellt der erste Hauptbeitrag der Dissertation einen neuen Ansatz zur AC dar, die so genannte erfahrungsbasierte Netzzugangskontrolle (engl. experience-based admission control, kurz EBAC). Gegenüber den existierenden alternativen, d.h. parameter- oder mess-basierten Verfahren der AC zeichnet sich die EBAC durch effiziente Ressourcennutzung und begünstigt gleichzeitig die Aufrechterhaltung der Dienstgüte. Die genaue Funktionsweise der EBAC und die simulative Leistungsuntersuchung sind in der Dissertation nachzulesen. Der zweite Themenschwerpunkt der Dissertation greift eine tunnel-basierte Netzarchitektur auf und präsentiert mit deren Hilfe eine neue Methode zur Bewertung verschiedener Bandbreitenallokationsstrategien in Kombination mit AC. Die neue Bewertungsmethode wird zwar anhand einer speziellen tunnel-basierten AC untersucht, lässt sich aber auf alle Arten so genannter budget-basierter AC anwenden. Bei der konventionellen Leistungsbewertung verschiedener AC-Systeme dienen abstrakte Blockierungswahrscheinlichkeiten als Leistungsmaß. Im Gegensatz hierzu, bewertet die neue Methode die Leistung eines AC-Systems anhand des zugehörigen Bandbreitenbedarfs in Abhängigkeit verschiedener Einflussfaktoren, z.B. der avisierten Blockierwahrscheinlichkeit des AC-Systems, der Verkehrszusammensetzung, des Verkehrsvolumens, der Verkehrsdynamik und vor allem der angewandten Bandbreitenallokationsstrategie. In zukünftigen IP Netzen müssen die Ressourcen zur Datenübertragung besser verwaltet und kontrolliert werden. Zugelassener Verkehr mit hohen Dienstgüteanforderungen muss exklusiv Bandbreite zugewiesen werden, um die geforderte Dienstgüte garantieren zu können. Um dieses Ziel zu erreichen werden robuste und effiziente Konzepte zum Management von Netzressourcen benötigt. Intelligenter Netzzugangskontrolle wird eine Schlüsselfunktion in zukünftigen IP Netzen zukommen. Die in dieser Dissertation vorgestellten, effizienten Ressourcenmanagementkonzepte „erfahrungsbasierte Netzzugangskontrolle“ und „adaptive Bandbreitenallokation in zugangskontrollierten Kapazitätstunnel“ tragen zum Erreichen dieses Ziels bei.

Satellites are some of the most difficult links to exploit in a Quality of Service (QoS) sensitive network, largely due to their high latency, variable-bandwidth and low-bandwidth nature. Central management of shared links has been shown to provide efficiency gains and enhanced QoS by effectively allocating resources according to reservations and dynamic resource availability. In a modern network, segregated by secure gateways and tunnels such as provided by IPsec, central management appears impossible to implement due to the barriers created between a global Dynamic Bandwidth Resource Allocation (DBRA) system and the mediators controlling the individual flows. This thesis explores and evaluates various through-IPsec communications techniques aimed at providing a satellite-to-network control channel, while maintaining data security for all communications involved.

Yuen Ka-nang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 133-135). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iii / Chapter 1. --- INTRODUCTION --- p.1 / Chapter 1.1. --- Background --- p.1 / Chapter 1.2. --- Objectives --- p.1 / Chapter 1.3. --- Overview of Thesis --- p.2 / Chapter 2. --- NETWORK ASPECT OF THE VOIP TECHNOLOGY --- p.3 / Chapter 2.1. --- VoIP Overview --- p.3 / Chapter 2.2. --- Elements in VoIP --- p.3 / Chapter 2.2.1. --- Call Setup --- p.3 / Chapter 2.2.2. --- Media Capture/Playback --- p.4 / Chapter 2.2.3. --- Media Encoding/Decoding --- p.4 / Chapter 2.2.4. --- Media Transportation --- p.5 / Chapter 2.3. --- Performance Factors Affecting VoIP --- p.6 / Chapter 2.3.1. --- Network Bandwidth --- p.6 / Chapter 2.3.2. --- Latency --- p.6 / Chapter 2.3.3. --- Packet Loss --- p.7 / Chapter 2.3.4. --- Voice Quality --- p.7 / Chapter 2.3.5. --- Quality of Service (QoS) --- p.7 / Chapter 2.4. --- Different Requirements of Intranet VoIP and Internet VoIP --- p.8 / Chapter 2.4.1. --- Packet Loss/Delay/Jitter --- p.8 / Chapter 2.4.2. --- Interoperability --- p.9 / Chapter 2.4.3. --- Available Bandwidth --- p.9 / Chapter 2.4.4. --- Security Requirement --- p.10 / Chapter 2.5. --- Some Feasibility Investigations --- p.10 / Chapter 2.5.1. --- Bandwidth Calculation --- p.10 / Chapter 2.5.2. --- Simulation --- p.12 / Chapter 2.5.3. --- Conclusion --- p.17 / Chapter 2.5.4. --- Simulation Restrictions --- p.17 / Chapter 3. --- SOFTWARE ASPECT OF THE VOIP TECHNOLOGY --- p.19 / Chapter 3.1. --- VoIP Client in JMF --- p.19 / Chapter 3.1.1. --- Architecture --- p.20 / Chapter 3.1.2. --- Incoming Voice Stream Handling --- p.23 / Chapter 3.1.3. --- Outgoing Voice Stream Handling --- p.23 / Chapter 3.1.4. --- Relation between Incoming/Outgoing Voice Stream Handling --- p.23 / Chapter 3.1.5. --- Areas for Further Improvement --- p.25 / Chapter 3.2. --- Capture/Playback Enhanced VoIP Client --- p.26 / Chapter 3.2.1. --- Architecture --- p.27 / Chapter 3.2.2. --- Native Voice Playback Mechanism --- p.29 / Chapter 3.2.3. --- Native Voice Capturing Mechanism --- p.31 / Chapter 3.3. --- Win32 C++ VoIP Client --- p.31 / Chapter 3.3.1. --- Objectives --- p.32 / Chapter 3.3.2. --- Architecture --- p.33 / Chapter 3.3.3. --- Problems and Solutions in Implementation --- p.37 / Chapter 3.4. --- Win32 DirectSound C++ VoIP Client --- p.38 / Chapter 3.4.1. --- Architecture --- p.39 / Chapter 3.4.2. --- DirectSound Voice Playback Mechanism --- p.40 / Chapter 3.4.3. --- DirectSound Voice Capturing Mechanism --- p.44 / Chapter 3.5. --- Testing VoIP Clients --- p.45 / Chapter 3.5.1. --- Setup of Experiment --- p.45 / Chapter 3.5.2. --- Experiment Results --- p.47 / Chapter 3.5.3. --- Experiment Conclusion --- p.48 / Chapter 3.6. --- Real-time Voice Stream Mixing Server --- p.48 / Chapter 3.6.1. --- Structure Overview --- p.48 / Chapter 3.6.2. --- Experiment --- p.53 / Chapter 3.6.3. --- Conclusion --- p.54 / Chapter 4. --- EXPERIMENTAL STUDIES --- p.55 / Chapter 4.1. --- Pure IP-side VoIP-based Call Center ´ؤ VoIP in Education --- p.55 / Chapter 4.1.1. --- Architecture --- p.55 / Chapter 4.1.2. --- Client Structure --- p.56 / Chapter 4.1.3. --- Client Applet User Interface --- p.58 / Chapter 4.1.4. --- Observations --- p.63 / Chapter 4.2. --- A Simple PBX Experiment --- p.63 / Chapter 4.2.1. --- Structural Overview --- p.63 / Chapter 4.2.2. --- PSTN Gateway Server Program --- p.64 / Chapter 4.2.3. --- Problems and Solutions in Implementation --- p.66 / Chapter 4.2.4. --- Experiment 1 --- p.66 / Chapter 4.2.5. --- Experiment 2 --- p.68 / Chapter 5. --- A COMPREHENSIVE VOIP PROJECT 一 GRADUATE SECOND PHONE (GSP) --- p.72 / Chapter 5.1. --- Overview --- p.72 / Chapter 5.1.1. --- Background --- p.72 / Chapter 5.1.2. --- Architecture --- p.76 / Chapter 5.1.3. --- Technologies Used --- p.78 / Chapter 5.1.4. --- Major Functions --- p.80 / Chapter 5.2. --- Client --- p.84 / Chapter 5.2.1. --- Structure Overview --- p.85 / Chapter 5.2.2. --- Connection Procedure --- p.89 / Chapter 5.2.3. --- User Interface --- p.91 / Chapter 5.2.4. --- Observations --- p.92 / Chapter 5.3. --- Gateway --- p.94 / Chapter 5.3.1. --- Structure Overview --- p.94 / Chapter 5.3.2. --- Connection Procedure --- p.97 / Chapter 5.3.3. --- Caller ID Simulator --- p.97 / Chapter 5.3.4. --- Observations --- p.98 / Chapter 5.4. --- Server --- p.101 / Chapter 5.4.1. --- Structure Overview --- p.101 / Chapter 5.5. --- Details of Major Functions --- p.103 / Chapter 5.5.1. --- Secure Local Voice Message Box --- p.104 / Chapter 5.5.2. --- Call Distribution --- p.106 / Chapter 5.5.3. --- Call Forward --- p.112 / Chapter 5.5.4. --- Call Transfer --- p.115 / Chapter 5.6. --- Experiments --- p.116 / Chapter 5.6.1. --- Secure Local Voice Message Box --- p.117 / Chapter 5.6.2. --- Call Distribution --- p.118 / Chapter 5.6.3. --- Call Forward --- p.121 / Chapter 5.6.4. --- Call Transfer --- p.122 / Chapter 5.6.5. --- Dial Out --- p.124 / Chapter 5.7. --- Observations --- p.125 / Chapter 5.8. --- Outlook --- p.126 / Chapter 5.9. --- Alternatives --- p.127 / Chapter 5.9.1. --- Netmeeting --- p.127 / Chapter 5.9.2. --- OpenH323 --- p.128 / Chapter 6. --- CONCLUSIONS --- p.129 / Bibliography --- p.133

Tese de mestrado. Redes e serviços de Comunicação. 2006. Faculdade de Engenharia. Universidade do Porto

Tese de mestrado. Redes e Serviços de Comunicação. Faculdade de Engenharia. Universidade do Porto. 2004

Tese de mestrado integrado. Engenharia Civil (especialização em Via de Comunicação). Faculdade de Engenharia. Universidade do Porto. 2008

Tese de mestr.. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 1998

Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores (Telecomunicações). Universidade do Porto. Faculdade de Engenharia. 2011

Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto, Instituto Superior de Engenharia de Coimbra. 2010

A research area that has recently gained great interest is the development of network architectures relating to the tracking of wireless VoIP devices. This is particularly so for architectures based on the popular Session Initiation Protocol (SIP). Previous work, however, in this area does not consider the impact of combined VoIP and tracking on the capacity and call set-up time of the architectures. Previous work also assumes that location information is always available from sources such as GPS, a scenario that rarely is found in practice. The inclusion of multiple positioning systems in tracking architectures has not been hitherto explored. It is the purpose of this thesis to design and test SIP-based architectures that address these key issues. Our first main contribution is the development of a tracking-only SIP based architecture. This architecture is designed for intermittent GPS availability, with wireless network tracking as the back-up positioning technology. Such a combined tracking system is more conducive with deployment in real-world environments. Our second main contribution is the development of SIP based tracking architectures that are specifically aimed at mobile wireless VoIP systems. A key aspect we investigate is the quantification of the capacity constraints imposed on VoIP-tracking architectures. We identify such capacity limits in terms of SIP call setup time and VoIP QoS metrics, and determine these limits through experimental measurement and theoretical analyses. Our third main contribution is the development of a novel SIP based location tracking architecture in which the VoIP application is modified. The key aspect of this architecture is the factor of two increase in capacity that it can accommodate relative to architectures utilizing standard VoIP. An important aspect of all our tracking architectures is the Tracking Server. This server supplies the location information in the event of GPS unavailability. A final contribution of this thesis is the development of novel particle-filter based tracking algorithms that specifically address the GPS intermittency issue. We show how these filters interact with other features of our SIP based architectures in a seamless fashion.