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Dissertation

Gateways and Components for Supplementary IP Telephony Services in Heterogeneous Environments

12 Aug 2003-
TL;DR: This work combines the investigation of a novel signaling gateway and infrastructure components for its integration with the design and realization of end-system with unique functionality and results in a model that facilitates the identification of general gateway structures and mechanisms that are appropriate for specific interworking requirements and scenarios.
Abstract: IP Telephony is a demanding interactive real-time service that already supplements the traditional telephony system to a considerable extent. It is expected to become a genuine alternative with a variety of new attractive services in the future. The recent situation and developments in the IP Telephony area are characterized by a variety of different usage environments, signaling approaches, protocols, devices and applications. We show that this situation, that is typically referred to as heterogeneity, has a number of inherent reasons and is not going to vanish within the near future. In many cases the different telephony components are not directly interoperable or their interaction is restricted to just a subset of the full capabilities. These circumstances make gateways that provide adequate interworking significant. Our central tenet is that gateways are appropriate and powerful means for dealing with heterogeneity. They are not restricted to the connection of legacy systems but play a significant constructive role for future setups as well. Their efficient design and realization is a challenging task. It is typically solved in a process that incorporates multiple steps. We investigate abstraction mechanisms that support this process. This investigation results in a model that facilitates the identification of general gateway structures and mechanisms that are appropriate for specific interworking requirements and scenarios. Our model fits between very high-level gateway descriptions and existing, but isolated best practice methods for particular gateway design problems. Our approach holistically covers multiple individual gateway aspects and tasks in the analysis and design process. We have chosen the interworking between the IP Telephony protocol suites H.323 and SIP for practical application of our methodology. Our efforts target large-scale IP Telephony deployment in real-world scenarios and the comprehensive and protocol-independent provisioning of supplementary services. The successful design and implementation of scalable interworking functionality for these services is the resulting practical contribution of this thesis. Our work combines the investigation of a novel signaling gateway and infrastructure components for its integration with the design and realization of end-system with unique functionality. Further, we categorize different types of media gateways and practically implement and investigate examples in this context. This activity and its outcome demonstrate the universality and power of our design and realization methodology. Additionally, we show that the combined and coordinated usage ofsignaling and media gateways is a powerful mechanism for future system designs. A practical example that uses this approach integrates low-resource decomposed wireless end-systems within our heterogeneous H.323 and SIP scenario. In the context of the presentation of general signaling gateways we show our contribution in the area of IP Telephony security. This includes the discussion of an IP Telephony enabled firewall that makes services usable in typical protected environments. The internal structure and the mechanisms of such a firewall are closely related to those of the investigated gateways. A practical IP Telephony vulnerability case study raises security problem awareness and motivates future activities with their implications on signaling gateways in this domain. Our contribution is practical as well as methodical. We have designed and realized new gateways and end-systems. These provide a novel quality for interworking in heterogeneous IP Telephony environments. It is not restricted to just basic call functionality but covers the very important and steadily extending range of supplementary services. Our gateway model and the problem analysis, design and realization methodology are general. The proof of concept implementations supplement it with instantiated templates for particular tasks. Model and templates together represent a framework that is applicable to solve various comparable interworking problems for IP-based communication systems efficiently.
Citations
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Book
01 Jan 2003
TL;DR: It is shown that recent security approaches are not sufficient and described how Security Patterns contribute to the overall process of security engineering, and a Security Pattern System provides linkage between Security Patterns.
Abstract: Conducting digital business requires secure network and application architectures. The recently increasing occurrence of severe attacks has shown, however, that we will still need quite some time and effort to reach security standards of IT systems alike the standard already usual in other fields. At present, there is a huge gap between theory and the code of practice. Whereas scientists work on formal approaches for the specification and verification of security requirements, practitioners have to meet the users requirements. The Pattern Community recognized this problem, too. Patterns literally capture the experience from experts in a structured way. Thus novices can benefit from know-how and skills of experts. Hence, we propose to apply the pattern approach to the security problem. We show that recent security approaches are not sufficient and describe how Security Patterns contribute to the overall process of security engineering. A Security Pattern System provides linkage between Security Patterns. Thus dependencies between specific security problems can be considered in a comprehensive way.

200 citations

Dissertation
03 Aug 2005
TL;DR: This dissertation addresses an expedient set of research challenges in the area of cellular and ad hoc networks by discussing the dependability—that is, the consistency of performance and behavior—of the routing system within such networks and analytically investigates the effects impaired by node misbehavior.
Abstract: This dissertation addresses an expedient set of research challenges in the area of cellular and ad hoc networks. In particular, we discuss the dependability—that is, the consistency of performance and behavior—of the routing system within such networks. Our restless, mobile society has inspired diverse fields of research in the area of computer communication networks. The results manifest in recent advances in the area of wireless and mobile communications, with cellular networks being an exemplar of success. Despite the fact of its supremacy in fixed networks, the Internet has not yet caught up in the mobile domain. We argue that next generation networks should overcome the dichotomy between the aforementioned networks and decide to focus our attention to the role of the routing system. We select cellular networks (closed to subscribers and based on infrastructure) and ad hoc networks (open/public and infrastructureless) to represent our objects of research. In Part I of the dissertation, we define the concept of routing dependability and identify the most important characteristics that influence this concept for the aforementioned networking paradigms. A mobility/workload model that captures the macroscopic effects of mobility for metropolitan areas is formulated and instantiated. Our results show that the effects of mobility acting upon the routing system cannot be neglected if we move towards smaller cell sizes and integration of hot spots in cellular systems. To cope with the observed mobility-induced traffic dynamics, we develop and evaluate architectures and algorithms in Part II of our work. In particular, we argue to broaden the scope of the routing domain towards the radio access tier of cellular networks ("smart edge"). In a first step, we break up today’s mainly hierarchically and treestructured cellular networks and introduce a meshed network topology, which adds flexibility to deploy distributed network control mechanisms. A comparative performance analysis of state-of-the-art routing protocols shows the feasibility of such control mechanisms for basic resource management in the surveyed networks. In a second step, a novel system architecture is designed that augments concepts from variable topology networks to cellular architectures. We also develop a routing algorithm to take advantage of the achieved flexibility. As a proof of concept, the algorithm is implemented and a simulation study is performed to obtain deeper insights in the algorithm’s operation. Our results show significant performance gains compared with current state-of-the-art algorithms. Ad hoc networks are effected by mobility as well. Moreover, they are built upon the premise of node cooperation. In Part III of this dissertation, we challenge such cooperation. Therefore, we analytically investigate the effects impaired by node misbehavior and contribute a model of the route acquisition process that includes different classes of node misbehavior. The model is formulated analytically and validated by means of an experimental analysis. Subsequently, an extensive simulation study is conducted to investigate the dependability trade-off between node mobility, routing protocol performance optimizations, and node misbehavior. Our results show clearly the performance degradation of the routing system, leading to network frailty for an increasing number of misbehaving nodes or increasing mobility, respectively.

17 citations

Dissertation
26 Jul 2006
TL;DR: In this dissertation, contributions are made towards developing a unified model for the performance analysis of QoS in the Internet, which integrates elements of system theory and queuing theory.
Abstract: Data flows belonging to multimedia applications are gaining importance in the Internet. A key characteristic of such data flows is that they require Quality of Service (QoS). An Internet populated with data flows requiring QoS constitutes a paradigm change from the Internet in its early days. This has been accounted for in many research endeavors proposing new architectures, algorithms and protocols. However, one area that has been relatively underexposed is the development of new models for QoS. Hence, the vision that has inspired this dissertation is the development of a unified model for the performance analysis of QoS in the Internet. The potential benefits of such a model can be observed in other fields: Linear system theory is widely used in the analysis of communication and control systems. In this dissertation, contributions are made towards developing a unified model for the performance analysis of QoS in the Internet. The basis of the work is network calculus. Network calculus is a system theory for deterministic queuing systems, which was developed in the 1990s. The underlying rationale is that deterministic QoS guarantees can be obtained by traffic regulation, deterministic scheduling and admission control. Beyond that, this work integrates elements of system theory and queuing theory. The latter has been the method of choice for modeling data flows in the Internet since its infancy. The main requirements of the envisioned model are that it should give insight on relevant characteristics, should have a wide range of applicability and should be transparent and easy to use. Recent research results in network calculus which address these requirements are presented. These include statistical network calculus and transforms. Further, some open issues are identified, which are then dealt with in this dissertation. A network calculus analysis is conducted for dynamically reconfigurable networks. First, the network architecture which can be found in optical networking is presented. The key feature here is that packet forwarding is not only influenced by the routing, but also by the reconfiguration. It is shown how service curves can be determined for different reconfiguration schemes, thus enabling a QoS analysis. On a more general footing, in this chapter it is illustrated how current networking research issues can be translated into network calculus models. The next contribution is the development of a new transform for network calculus and its application. With the new transform the min-plus convolution, which is an important operation in network calculus, obtains a graphical interpretation and thus becomes easier to use. Based on the transform, theorems on the computation of the min-plus convolution are set up. These theorems are then applied to network design using service curves, with an emphasis on bandwidth/delay decoupled scheduling. Furthermore, network calculus and queuing theory are brought together. While network calculus focuses on the worst case analysis, queuing theory deals mainly with average behavior. It is examined whether the best of both worlds can be combined to achieve better models. First, analytical approaches are presented, which are then followed by a simulation. Finally, the achieved progress is summarized and some conclusions drawn.

12 citations

Patent
28 Sep 2005
TL;DR: In this paper, a method for supporting advanced features in a core SIP network when the calling party is in a network operating with the H.450.323 protocol is disclosed.
Abstract: A method for supporting advanced features in a core SIP network when the calling party is in a network operating with the H.323 protocol is disclosed. Specifically, after processing the calls by collecting information associated with the advanced features, a REFER message is sent by an application server to an ingress border element associated with the calling party. The ingress border element then sends an H.450.2 FACILITY message containing the information in the SIP REFER message to an application gateway associated with the calling party. Upon receiving a SETUP message from the application gateway, the ingress border element then translates that SETUP message into a SIP INVITE message to establish the call.

8 citations

Patent
23 Jul 2008
TL;DR: In this article, a call transfer technique between multiple application servers in a SIP-based network or other type of communication network is disclosed. But it is assumed that a first call is established between a first user device and a second user device via a first server, and the second user devices, wishing to initiate call transfer to a third user device, establishes a second call between itself and the third user devices via a second server.
Abstract: Call transfer techniques between multiple application servers in a SIP-based network or other type of communication network are disclosed. In accordance with one example technique of the invention, it is assumed that a first call is established between a first user device and a second user device via a first server, and the second user device, wishing to initiate a call transfer to a third user device, establishes a second call between itself and the third user device via a second server. Thus, the technique includes the following steps. Upon the first server receiving a call transfer request from the second user device such that the first user device and the third user device can communicate, it is determined whether the first server has information that matches the second call. Upon determining that the first server does not have information matching the second call, a message is sent from the first server to the second server so as to obtain information from the third device such that the first user device and the third user device can communicate via the first server. The message sent from the first server to the second server indicates that the call transfer request was referred by the second user device.

8 citations

References
More filters
01 Jul 2003
TL;DR: RTP provides end-to-end network transport functions suitable for applications transmitting real-time data over multicast or unicast network services and is augmented by a control protocol (RTCP) to allow monitoring of the data delivery in a manner scalable to large multicast networks.
Abstract: This memorandum describes RTP, the real-time transport protocol. RTP provides end-to-end network transport functions suitable for applications transmitting real-time data, such as audio, video or simulation data, over multicast or unicast network services. RTP does not address resource reservation and does not guarantee quality-of-service for real-time services. The data transport is augmented by a control protocol (RTCP) to allow monitoring of the data delivery in a manner scalable to large multicast networks, and to provide minimal control and identification functionality. RTP and RTCP are designed to be independent of the underlying transport and network layers. The protocol supports the use of RTP-level translators and mixers.

7,183 citations


"Gateways and Components for Supplem..." refers methods in this paper

  • ...The Real-time Transport Protocol RTP [149] is generally used for media transport within the various IP Telephony protocol suites....

    [...]

Journal ArticleDOI
TL;DR: A switch actuating device adapted for conjoint rotation with a rotatable assembly of a prime mover using a pair of sets of opposite surfaces to effect the axial movement of the switch operating means between its opposite positions.
Abstract: A switch actuating device adapted for conjoint rotation with a rotatable assembly of a prime mover. Means for mounting to the rotatable assembly so as to be conjointly rotatable therewith includes a pair of sets of opposite surfaces, and switch operating means conjointly rotatable with the mounting means is arranged for axial movement thereon between a pair of opposite positions. A pair of centrifugal weight members are responsive to the rotational speed of the device to effect the axial movement of the switch operating means between its opposite positions and include a pair of sets of means arranged for guiding engagement on the oppposite surface set pair upon the axial movement of the switch operating means between its opposite positions, respectively. A pair of springs are respectively biased between the centrifugal members. A method of assembling a switch actuating device is also disclosed.

1,826 citations


"Gateways and Components for Supplem..." refers methods in this paper

  • ...It uses the well known model-view-controller (MVC) pattern [103]....

    [...]

Book
Gerard J. Holzmann1
01 Jan 1991
TL;DR: Part 1 Basic: introduction protocol structure error control flow control and design tools: a protocol simulator a protocol validator using the validator.
Abstract: Part 1 Basic: introduction protocol structure error control flow control. Part 2 Specification and modeling: validation models correctness requirements protocol design finite state machines. Part 3 Conformance testing synthesis and validation: conformance testing protocol synthesis protocol validation. Part 4 Design tools: a protocol simulator a protocol validator using the validator.

1,655 citations


"Gateways and Components for Supplem..." refers methods in this paper

  • ...[67] formulates a general procedure for the successful design of computer protocols....

    [...]

Journal ArticleDOI
TL;DR: LOTOS is a specification language that has been specifically developed for the formal description of the OSI (Open Systems Interconnection) architecture, although it is applicable to distributed, concurrent systems in general.
Abstract: LOTOS is a specification language that has been specifically developed for the formal description of the OSI (Open Systems Interconnection) architecture, although it is applicable to distributed, concurrent systems in general. In LOTOS a system is seen as a set of processes which interact and exchange data with each other and with their environment. LOTOS is expected to become an ISO international standard by 1988.

1,446 citations


"Gateways and Components for Supplem..." refers methods in this paper

  • ...It uses the system description language LOTOS [35] and extends existing UML description mechanisms [26]....

    [...]

01 Jan 2003
TL;DR: Bar attributes op1() op2() Abstract Operation (in italic) is defined to describe the operation of the Bar variable.
Abstract: public class Bar{ abstract public void op1(); public void op2(){} } Bar attributes op1() op2() Abstract Operation (in italic)

1,092 citations