There is a growing interest in the development of broadband services and networks for commercial use in both local area and wide area networks. The primary reasons for this is a pressing need to meet the demand for increased bandwidth for remote sites interconnection, and in high speed data transfer of bulk data such as images etc. There has also been a significant change in the characteristics of network traffic. It is increasingly taking the form of bursty traffic characterized by an unpredictable demand for bandwidth of several megabytes. A new generation of networking technologies have emerged to meet the demand of growing and uncertain bandwidth requirements. One such technology is called Asynchronous Transfer Mode (ATM) for use on broadband networks under the banner of broadband ISDN. ATM enables interconnection at high speeds in the range of Mbit/s or Gbit/s over wide areas, which effectively moves the bottleneck from networks to end systems. Furthermore, the user is able to access bandwidth on demand and the user is only charged for the bandwidth actually used. As more and more information (audio, image and data) is transferred over ATM networks, security issues are becoming increasingly critical. The rapidly growing use of the Internet to transfer confidential and sensitive information only enhances the importance of security services. One may even argue that the success of ATM will be determined not by its cost effectiveness but also to the level of trust that can be placed on its performance, security and availability. The objective of this dissertation is to address the issues involved in the design of security services for ATM networks. / Master of Science (Hons)

The research presented in this thesis aims to demonstrate that fuzzy logic is a useful tool for developing mechanisms for controlling traffc flow in ATM based multimedia networks to maintain quality of service (QoS) requirements and maximize resource utilization. The study first proposes a hierarchical, multilevel control structure for ATM networks to exploit the reported strengths of fuzzy logic at various control levels. Then, an extensive development and evaluation is presented for a subset of the proposed control architecture at the congestion control level. An ATM based multimedia network must have quite sophisticated traffc control capabilities to effectively handle the requirements of a dynamically varying mixture of voice, video and data services while meeting the required levels of performance. Feedback control techniques have an essential role for the effective and efficient management of the resources of ATM networks. However, development of conventional feedback control techniques relies on the availability of analytical system models. The characteristics of ATM networks and the complexity of service requirements cause the analytical modeling to be very difficult, if not impossible. The lack of realistic dynamic explicit models leads to substantial problems in developing control solutions for B-ISDN networks. This limits the ability of conventional techniques to directly address the control objectives for ATM networks. In the literature, several connection admission and congestion control methods for B-ISDN networks have been reported, and these have achieved mixed success. Usually they either assume heavily simplified models, or they are too complicated to implement, mainly derived using probabilistic (steady-state) models. Fuzzy logic controllers, on the other hand, have been applied successfully to the task of controlling systems for which analytical models are not easily obtainable. Fuzzy logic control is a knowledge-based control strategy that can be utilized when an explicit model of a system is not available or, the model itself, if available, is highly complex and nonlinear. In this case, the problem of control system design is based on qualitative and/or empirically acquired knowledge regarding the operation of the system. Representation of qualitative or empirically acquired knowledge in a fuzzy logic controller is achieved by linguistic expressions in the form of fuzzy relational equations. By using fuzzy relational equations, classifications related to system parameters can be derived without explicit description. The thesis presents a new predictive congestion control scheme, Fuzzy Explicit Rate Marking (FERM), which aims to avoid congestion, and by doing so minimize the cell losses, attain high server utilization, and maintain the fair use of links. The performance of the FERM scheme is extremely competitive with that of control schemes developed using traditional methods over a considerable period of time. The results of the study demonstrate that fuzzy logic control is a highly effective design tool for this type of problems, relative to the traditional methods. When controlled systems are highly nonlinear and complex, it keeps the human insight alive and accessible at the lower levels of the control hierarchy, and so higher levels can be built on this understanding. Additionally, the FERM scheme has been extended to adaptively tune (A-FERM) so that continuous automatic tuning of the parameters can be achieved, and thus be more adaptive to system changes leading to better utilization of network bandwidth. This achieves a level of robustness that is not exhibited by other congestion control schemes reported in the literature. In this work, the focus is on ATM networks rather than IP based networks. For historical reasons, and due to fundamental philosophical differences in the (earlier) approach to congestion control, the research for control of TCP/IP and ATM based networks proceeded separately. However, some convergence between them has recently become evident. In the TCP/IP literature proposals have appeared on active queue management in routers, and Explicit Congestion Notication (ECN) for IP. It is reasonably expected that, the algorithms developed in this study will be applicable to IP based multimedia networks as well.

We have chosen to look closer at the area of security for electronic invoices. The purpose of this inquest is to provide our case study with a security analysis of three suggestions and a recommendation of the best solution, according to our test. The three solutions are ISDN via a third party, X.25 via Internet bank and Mail server. The company in our case study is in this report referred to as X, has a strong market position and a large clientele and therefore we were interested in analysing and improving X?s electronic invoice system. X was in the position of testing an electronic invoicing system towards a selective group of business customers. The major problem with the system was the security issue regarding transferring the file.

Der Asynchronous Transfer Mode (ATM) stellt die zukünftige und einheitliche Basistechnologie für das Breitband-ISDN dar. Da nahezu alle wesentlichen Protokollfunktionen in Hardware realisierbar sind, soll nachfolgend ein Überblick über bereits angebotene VLSI-Schaltkreise gegeben werden. Eine Systematisierung und Einordnung vorhandener ATM-Chips hinsichtlich ihrer Leistungsfähigkeit und ihres Funktionsumfangs erfolgt in Hinblick auf das sogenannte B-ISDN-Referenzmodell. Dieses Schichtenmodell definiert die notwendigen Protokolle und Schnittstellen für den Asynchronous Transfer Mode. Zum grundlegenden Verständnis wird einleitend eine kurze Einführung in die Basisprinzipien von ATM gegeben.

Within the fields of network operation and performance measurement, it is a common requirement that the technologies involved must provide the basis for an effective, reliable, measurable and controllable service. In order to comply with the service performance criteria, the constrains often lead to very complex techniques and methodologies for the simulation, control, test, and measurement processes. This thesis addresses some of the factors that contribute to the overall spectrum of statistical performance measurements in telecommunication services. Specifically, it is concerned with the development of three low complexity and effective techniques for real-time traffic generation, control and measurement. These techniques have proved to be accurate and near optimum. In the three cases the work starts with a literature survey of known methodologies, and later new techniques are proposed and investigated by simulating the processes involved. The work is based on the use of high-speed Asynchronous Transfer Mode (ATM) networks. The problem of developing a fast traffic generation technique for the simulation of Variable Bit Rate traffic sources is considered in the first part of this thesis. For this purpose, statistical measures are obtained from the analysis of different traffic profiles or from the literature. With the aid of these measures, a model for the fast generation of Variable Bit Rate traffic at different time resolutions is developed. The simulated traffic is then analysed in order to obtain the equivalent set of statistical measures and these are compared against those observed in real traffic traces. The subject of traffic control comprises a very wide area in communication networks. It refers to the generalised classification of actions such as Connection Admission and Flow Control, Traffic Policing and Shaping. In the second part of this thesis, a method to modify the instantaneous traffic profile of a variable rate source is developed. It is particularly useful for services which have a hard bound on the cell loss probability, but a soft bound on the admissible delay, matching the characteristics of some of the services provided by ATM networks. Finally, this thesis is also concerned with a particular aspect of the operation and management of high speed networks, or OAM functions plane, namely with the monitoring of network resources. A monitoring technique based on numerical approximation and statistical sampling methods is developed and later used to characterise a particular traffic stream, or a particular connection, within a high speed network. The resulting algorithms are simple and computationally inexpensive, but effective and accurate at the same time, and are suitable for real-time processing.

Στην παρούσα διπλωματική εργασία μελετάται έλεγχος της λειτουργίας ενός πλήθους διαφορετικών τεχνολογιών δικτύου, όπως το Ψηφιακό Δίκτυο Ενοποιημένων Υπηρεσιών (Integrated Services Digital Network, ISDN), ο ψηφιακός βρόχος συνδρομητή (Digital Subscriber Loop), οι τεχνολογίες SHDSL,VDSL κ.α. Αφότου έγινε μια εκτενής περιγραφή των περισσότερων τύπων δικτύων και διεξοδική μελέτη των λειτουργιών τους, προσδιορίστηκαν οι τεχνολογίες δικτύου που είναι εφικτό να μελετηθούν στα πλαίσια ενός εργαστηριακού μαθήματος. Για την επίτευξη του στόχου αυτού δη-μιουργήθηκαν μια σειρά εργαστηριακών ασκήσεων που βοηθούν στην κατανόηση τόσο των συγκεκριμένων τεχνολογιών (και των μεταξύ τους διαφορών) όσο και των πολυάριθμων ελέγχων που είναι δυνατό να διεξαχθούν για την παρακολούθηση και συντήρηση των συγκεκριμένων δικτύων. Εν κατακλείδι η εργασία αποτελεί ένα χρήσιμο εργαλείο για τη μελέτη των πιο σημαντικών τεχνολογιών δικτύου. / This diploma thesis examines the monitoring of the functions, of many network technologies such as the Integrated Services Digital Network (ISDN), the Digital Subscriber Loop (DSL), the SHDSL, VDSL technologies and more. After an extensive reference of the most network types and a comprehensive study of their functions, it has been determined which of those is possible to be examined as a part of lab course. In order for this goal to be achieved, it has been created a set of laboratory exercises that help in the understanding of these network technologies, the differences between them and the multiple tests that can be conducted for the monitoring and maintenance of those networks. In conclusion this diploma thesis is useful tool in the study of the most important network technologies.

This master’s thesis dissertate the possibilities of the linkage between Asterisk softswitch and the 4th generation private branch exchange. This should create a new generation’s network, so-called NGN, by the convergence of existing telecommunication networks with an IP computer network. This master’s thesis is divided into several chapters. In introduction is described the evolution of the private branch exchanges as well as the principles of the voice digitizing, codecs and signaling commonly used in both TDM and VoIP networks. The main aim of this project is the configuration of Asterisk software exchange for connection with PBX Alcatel 4400 as well as public phone network PSTN. Another goal of this master’s thesis was the configuration of Alcatel PBX and diagnostics of CCS and CAS signaling on E1 interface. In conclusion there are summarized advantages of NGN networks and their utilization in the future.

Der Asynchronous Transfer Mode (ATM) stellt die zukünftige und einheitliche Basistechnologie für das Breitband-ISDN dar. Da nahezu alle wesentlichen Protokollfunktionen in Hardware realisierbar sind, soll nachfolgend ein Überblick über bereits angebotene VLSI-Schaltkreise gegeben werden. Eine Systematisierung und Einordnung vorhandener ATM-Chips hinsichtlich ihrer Leistungsfähigkeit und ihres Funktionsumfangs erfolgt in Hinblick auf das sogenannte B-ISDN-Referenzmodell. Dieses Schichtenmodell definiert die notwendigen Protokolle und Schnittstellen für den Asynchronous Transfer Mode. Zum grundlegenden Verständnis wird einleitend eine kurze Einführung in die Basisprinzipien von ATM gegeben.

The end of the Twentieth Century and the start of the Twenty First Century has been a tumultuous time for the Telecommunications Industry. Even as it moves forward to embrace the new technologies the Industry finds itself embroiled in issues of governance. The Industry finds itself in a dilemma since innovations increase at a rate faster than the laws can be changed and these render its existing laws and policies to be in some cases obsolete and inappropriate for the reality of the present. In the past, the United States of America has relied on vertically integrated top down laws and methods of regulating all the different parts in its Telecommunications Industry. These laws are contained in the different numbered Titles of this Countrys Legal Codes. Since the inception of these laws, emphasis was placed in creating and documenting policies structured by industry, sector and type of content. This form of regulation is usually referred to as the Silo Method. However, in recent years, especially in the regulation of the Telephony industry, the method of law and rule formulation moved from content regulation to one in which the technologies are getting regulated in what has been described as a Layers Method. This paper first considered whether the Silo Method of regulation is in actuality the same as using the Horizontal Layers method and showed that this is the case. Then it determined that Enhanced Services are the same as Basic Services and that Telecommunications Services are the same as Information services and showed that given that the pair sets as noted were the same, it went on to conclude that all these services were essentially the same. While studying to some detail the technologies of VoIP, the paper also showed that VoIP although an Internet technology is similar to traditional telephony, and is both a Telecommunications Service and Information Service based on the definition as given in the law as well as the technologies that are used and that as a result of this, the current regulatory environment for this service with regards to telephony is inconsistent. It concluded that Telecommunications policies though now adequate may need to be modified.