Prof. Dr. Dieter Hogrefe
Position:
Head of Telematics Group
Phone:
+49 (551) 39-1 44 01/02
Fax:
+49 (551) 39-1 44 03
Office:
SW 0.120
Email:
Address:
How to find us Links Citations Publications Research Projects Service to the Scientific Community Exchange OWA Curriculum Vitae Dieter Hogrefe is full professor (C4) for Telematics at the University of Göttingen since 2002. He graduated at Philips Exeter Academy, USA, in 1976 and studied Computer Science and Mathematics at the University of Hannover, Germany, where he graduated with a diploma degree and PhD. His research activities are directed towards Computer Networks and Communication Software Engineering. He published numerous papers and two books on Internet technology, analysis, simulation and testing of formally specified communication systems. Prof. Hogrefe held full professor positions at the Universities of Dortmund, Bern, Lübeck, and Göttingen and visiting positions at UC Berkeley and Hamilton University.
From 1983 to 1986 he was with the SIEMENS research centre in Munich and worked in the area of analysis of telecommunication systems. He was responsible for the protocol simulation and analysis of the CCS No. 7. Since 1996 Prof. Hogrefe is chairman of the Technical Committee Methods for Testing and Specification at the European Telecommunication Standards Institute, ETSI. He is married to Susan Hogrefe and has four children (Christian 1989, Luise 1990, Georg 1993 and Katharina 1998).
Research Projects
Publications
2008
Performance Study of PANA Pre-authentication for Interdomain Handover ,
Omar Alfandi , Henrik Brosenne , Patryk Chamuczynski , Dieter Hogrefe , Constantin Werner , The Fourth International Conference on Networking and Services (ICNS 2008), Gosier, Guadeloupe,
March 2008.
Read abstract
To provide seamless mobility to the wireless user, a
continuous connection to the Internet is required while moving from one administration domain to another. To enable continuous connectivity, one prerequisite is the incorporation of seamless handover. The make-before-break approach facilitates seamless handover by means of executing an authentication to a new domain simultaneously while maintaining connection to current domain. The connection is only terminated after the handover to the new domain is successfully completed.
However, the duration of the authentication is critical for
the handover process because if the mobile nodes move very
fast the remaining amount of time of connection to the current domain can become very limited. Therefore, it is a vital issue for seamless mobility to study the authentication performance of a pre-authentication framework.
In this paper we model an authentication infrastructure
and consider a scenario in which a high number of nodes
handover to a new administration domain. The simulation of the authentication process shows the relation between authentication performance and traffic intensity. Furthermore we identify some critical points and potential bottlenecks of this pre-authentication approach.
PDF [344.3 kB]
Fast Re-Authentication for Inter-Domain Handover using Context Transfer ,
Omar Alfandi , Henrik Brosenne , Dieter Hogrefe , Constantin Werner , The International Conference on Information Networking 2008 (ICOIN 2008), Busan, Korea,
January 2008.
Read abstract
The exponential growth of wireless mobile systems in recent years has created strong demand to handover between different administration domains. Such movement suffers from limited resources such as limited bandwidth and high latency. Furthermore, authentication is the key factor when providing mobile roaming services, so fast re-authentication is one of the important issues to achieve a short overall handover delay. Therefore, it is important to develop techniques that utilize the available bandwidth efficiently. One way of utilizing the wireless resources efficiently is by transferring the required context that authenticates the user in new visited domain of the running session rather than establishing the connection from scratch. Current approaches only consider a repeated authentication process run for a new visited domain and therefore, can potentially introduce high latency by communicating with authorization services of a home domain. In this paper, we propose a novel way to authenticate a mobile node without the necessity to communicate with the home domain while maintaining a high level of security. We provide an overview of the method, show the improvement to related approaches in terms of message flows and discuss security aspects.
PDF [422.0 kB]
2007
Comparative Studies on Authentication and Key Exchange Methods for 802.11 Wireless LAN ,
Xiaoming Fu , Dieter Hogrefe , Jun Lei , Jianrong Tan, Computers & Security, Volume 26, Issue 5, Pages 401-409,
Elsevier, ISSN 0167-4048, August 2007.
Read abstract
IEEE 802.11 wireless LAN has become one of the hot topics on the design and development of network access technologies. In particular, its authentication and key exchange (AKE) aspects, which form a vital building block for modern security mechanisms, deserve further investigation. In this paper we first identify the general requirements used for WLAN authentication and key exchange (AKE) methods, and then classify them into three levels (mandatory, recommended, and additional operational requirements). We present a review of issues and proposed solutions for AKE in 802.11 WLANs. Three types of existing methods for addressing AKE issues are identified, namely, the legacy, layered and access control-based AKE methods. Then, we compare these methods against the identified requirements. Based on the analysis, a multi-layer AKE framework is proposed, together with a set of design guidelines, which aims at a flexible, extensible and efficient security as well as easy deployment.
PDF [116.1 kB]
E2T: End-to-End Tunnelling Extension to Mobile IPv6 ,
Xiaoming Fu , Dieter Hogrefe , Deguang Le , and Xiaoyuan Gu, in Proceedings of the 4th IEEE Consumer Communications and Networking Conference (CCNC 2007), Las Vegas, Nevada, USA,
IEEE Communications Society, January 2007.
Read abstract
In the standard Mobile IPv6 (MIPv6), the bidirectional tunnelling through the home agent or the route optimization show inefficiency in per-packet routing, especially when both communicating endpoints are mobile. To be scalable and compatible, mobile devices? packets should be routed efficiently with minimal changes to the network infrastructure. However, the current solutions do not provide any means for the end systems to perform optimized packet routing during the operation of the mobile devices. In this paper, we present an end-to-end tunnelling extension to MIPv6 (E2T) for mobile routing packets, which reduces the per-packet routing cost for the communications of mobile devices through the lower packet routing overhead. Besides, our approach requires little change to MIPv6, but allows the more efficient routing behavior with the shorter end-to-end transmission latency between communicating endpoints. The simulation results show our approach is suitable for real-time multimedia applications.
PDF [357.5 kB]
DMMP: A New Dynamic Mesh-based Overlay Multicast Protocol Framework ,
Xiaoming Fu , Dieter Hogrefe , Jun Lei , Proceedings of the 2007 IEEE Consumer Communications and Networking Conference - Workshop on Peer-to-Peer Multicasting (P2PM 2007), Las Vegas, Nevada, USA,
IEEE Communications Society, January 2007.
Read abstract
Multicasting can provide an efficient way of delivering data from a sender to a group of receivers. It has received much attention over the past decade because of an increasing demand for group communication applications such as multimedia streaming. However, native IP multicast has not become widespread largely due to its technical and operational issues. To overcome these obstacles of deployment, various application layer and overlay multicast approaches have been proposed. Compared with IP multicast, they provide a new way of handling multicast without upgrading the infrastructure in a large scale. Nevertheless, they introduce a number of challenges and are still plagued with concerns on scalability, heterogeneity and dynamic performance. In this paper we propose a new protocol framework for addressing these issues, so-called the Dynamic Mesh-based Overlay Multicast Protocol or DMMP, which intends to provide an efficient and resilient multicast support by dynamically managing an overlay core comprised of end hosts. Moreover, DMMP can be used for media streaming which is contracted by a limited resource in stream supplying entities and requires good scalability and reliability. Initial analysis shows that DMMP has the potential to efficiently deliver multicast services for large groups.
PDF [311.3 kB]
2006
Beyond QoS Signaling: a Generic IP Signaling Framework ,
Xiaoming Fu , Dieter Hogrefe , and Hannes Tschofenig, Computer Networks, Volume 50, Issue 17, pages 3416-3433,
Elsevier, December 2006.
Read abstract
This paper describes the design principles and an introduction of a framework and protocols for generic IP signaling, namely the Cross-Application Signaling Protocol (CASP) and its signaling applications. While reusing certain features of the existing RSVP protocol, CASP overcomes its shortcomings and may be deployed as a replacement technology to provide simpler, mobility-supported, more extensible and more secure signaling services in IP based networks. This paper discusses challenges of today?s IP signaling protocols and addresses fundamentals and key aspects of CASP and its current signaling applications. In addition, a comparison with previous signaling protocol proposals and an outlook of future work in this area are also given.
PDF [272.8 kB]
A UML Profile for Communicating Systems ,
Dieter Hogrefe , Constantin Werner , Sebastian Kraatz, in: Gotzhein, Reed: System Analysis and Modeling: Language Profiles, 5th International Workshop, SAM 2006, Kaiserslautern, Germany, May 31 - June 2, 2006, Revised Selected Papers, pp. 1-18,
Springer Verlag, ISSN 0302-9743, December 2006.
Read abstract
This paper presents a UML 2 profile for communicating systems. It is driven by the experience of SDL and uses formal constraints for profile definition and mapping rules by means of OCL. It features language elements for high-level specification and description of Internet communication and signaling protocols where SDL is not optimally suited. Due to its support of several concrete notations, this profile is aligned to work with several UML 2 compliant modeling tools. In addition, an implementation by an XSLT-based mapping from UML to behavioral and structural SDL specifications is available. The intention of the paper is to present the main work done which is defining an actual profile and mapping this to SDL.
Internet und Kommunikation: zuverlässig, sicher, allgegenwärtig? ,
Dieter Hogrefe ,
Vandenhoeck & Ruprecht, December 2006.
Read abstract
Wir alle nutzen heute das Internet auf vielfältige Arten und Weisen: Bankgeschäfte, Telefonieren, Kaufen/Verkaufen, Informationen aller Art beschaffen oder Spielen. Inwieweit kann man dem Medium eigentlich trauen, das man da nutzt, wie verlässlich ist es eigentlich im Sinne der Bereitstellung eines Dienstes zu einer bestimmten Zeit an einem bestimmten Ort in der gewünschten Qualität und Sicherheit?
Es ist davon auszugehen und wird sogar von den Nutzern zunehmend erwartet, dass das Internet in der Zukunft allgegenwärtig ist, wir also ständig und überall darauf Zugriff haben, so wie wir heute ständig und überall telefonieren können, wenn wir möchten, ohne auf Telefonzellen und Kleingeld angewiesen zu sein. Wenn man mal kein ?Handynetz? hat, sich z.B. in einem Funkloch befindet, wird das bereits als großer Mangel empfunden: ?Wo sind wir denn hier gelandet??. Was heute für das Telefonieren gilt, wird morgen für den Zugriff auf das Internet mit all seinen Informationsmöglichkeiten gelten. Eigentlich befinden wir uns bereits in diesem Zustand, ohne dass die Gesellschaft das wirklich realisiert. Allerdings hat der ubiquitäre (allgegenwärtige) Internetzugang derzeit noch immer Experimentiercharakter, ist also derzeit eher etwas für eingeweihte Bastler. Das wird sich allerdings ändern. Es ist dabei festzustellen, dass der ubiquitäre Internetzugang eine ökonomische Fragestellung ist, d.h. immer und überall online sein, wird generell teurer sein, als z.B. gelegentlich vom häuslichen DSL-Anschluss das Internet zu nutzen.
In dieser Situation des allgegenwärtigen Internets, stellt sich schnell die berühmte ?Big Brother is watching you?-Frage: Was ist eigentlich mit Vertraulichkeit, Privatsphäre, also Sicherheit im Allgemeinen?
Es gibt eine Reihe von Sicherheitsinstrumenten wie Verschlüsselung, Authentifizierung, etc., die viele von uns nutzen. Im Allgemeinen soll ein Sicherheits-Mechanismus dazu da sein, gegen böswillige Beteiligte zu schützen. Wenn man das so versteht, dann gibt es aber eine ganze Menge Sicherheitsherausforderungen, denen nicht mit herkömmlichen Instrumenten begegnet werden kann. Traditionelle Instrumente schützen typischerweise Ressourcen vor böswilligen Nutzern, indem der Zugriff nur den autorisierten Nutzern gewährt wird. Allerdings muss sich der einzelne Benutzer selbst auch oft gegen solche Beteiligte schützen, die böswillige Dienste anbieten. Technisch gesehen geht das in manchen Fällen mit Firewalls, allerdings nur auf sehr niedriger semantischer Ebene. Es geht z.B. dann nicht, wenn wir explizit Dienste in Anspruch nehmen möchten und nicht wissen, ob sie böswillig sind oder nicht. So könnte z.B. ein Informationsanbieter zu seinem eigenen Vorteil absichtlich falsche Informationen anbieten. Dagegen können die traditionellen Sicherheitsmechanismen nicht schützen.
Um diesen Sicherheitsherausforderungen zu begegnen, geraten sog. Vertrauens- und Reputationssysteme immer mehr in den Blickpunkt. Man bezeichnet das neuerdings auch als ?Soft-Security? im Gegensatz zu der herkömmlichen ?Hard-Security?.
Akademievortrag-Publ.pdf [103.7 kB]
Dynamic Mesh-based overlay Multicast Protocol (DMMP) ,
Xiaoming Fu , Dieter Hogrefe , Jun Lei , Internet Research Task Force, Internet draft (draft-lei-samrg-dmmp-01), work in progress, Scalable Adaptive Multicast (SAM) Research Group,
October 2006.
Read abstract
This document describes a Dynamic Mesh-based overlay Multicast Protocol (DMMP) to support multicast data delivery applications without relying on classic IP multicast, including multicast group management, overlay hierarchy establishment, multicast tree construction and data forwarding scheme from the source to a number of receivers. The DMMP framework builds on control plane functions which dynamically manage an overlay core and a multicast tree layer. The key idea is a number of end hosts self-organize into an overlay mesh, and dynamically maintain such a mesh. Based on the constructed mesh, some core-based clusters are built with capacity-aware trees inside. Then, a multicast tree consisting of DMMP-aware end hosts (and/or specific routers) is built on the top of the overlay core for the efficient delivery of the multicast data.
PDF [64.0 kB]
An Evaluation of Multi-Role Access Routers: Specification and Validation of an IDKE aware Access Router ,
Dieter Hogrefe , Rene Soltwisch , Constantin Werner , Proceedings of the IEEE International Conference on Networks (ICON) 2006, Singapore,
September 2006.
Optimising WiMAX Business Models using Incentive Engineering ,
Dieter Hogrefe , André Riedel , Timo Fischer, IEEE International Conference on Networks (ICON?06),
September 2006.
DMMP: A New Dynamic Mesh-based Overlay Multicast Protocol Framework ,
Xiaoming Fu , Dieter Hogrefe , Jun Lei , Technical Report No. IFI?TB?2006?05, Institute for Informatics, University of Goettingen, Germany,
ISSN 1611-1044, July 2006.
Read abstract
Multicasting provides an efficient way of delivering data from a sender to a group of receivers. It has been gained much attention over the past decade because of an increasing demand for group communication applications such as multimedia streaming. Compared with network layer multicast solutions, recent application-layer multicast and overlay multicast approaches provide a new way of handling multicast without upgrading the infrastructure in a large scale. Meanwhile, they introduce a number of challenges and are still plagued with concerns pertaining to scalability, deployment, heterogeneity and dynamic performance. In this paper we propose a new protocol framework for relieving these issues, so-called the Dynamic Mesh-based Overlay Multicast Protocol or DMMP, which intends to provide an efficient and reliable multicast support by dynamically managing an overlay core comprised of end hosts. Although more analysis and evaluation is necessary, this paper sheds light on several identified design issues with DMMP and initially analyzes its performance.
PDF [689.2 kB]
UML Profile for Communicating Systems ,
Dieter Hogrefe , Constantin Werner , Sebastian Kraatz, Proceedings of SAM'06 -- Fifth Workshop on System Analysis and Modelling (formerly SDL and MSC Workshop), May 31st-June 2nd 2006, University of Kaiserslautern, Kaiserslautern, Germany, pp. 81-90,
June 2006.
Modelling Soft-State Protocols with SDL ,
Xiaoming Fu , Dieter Hogrefe , IEE Proceedings Communications,
ISSN 1350-2425, Volume 153, Issue 3, pages 365-375, June 2006.
Overhead and Performance Study of the General Internet Signaling Transport (GIST) Protocol ,
Xiaoming Fu , Dieter Hogrefe , Henning Schulzrinne, Hannes Tschofenig, and Christian Dickmann, IEEE INFOCOM 2006, Bacelona, Spain,
IEEE, April 2006.
Read abstract
The General Internet Signaling Transport (GIST) protocol is currently being developed as the base protocol component in the IETF Next Steps In Signaling (NSIS) protocol stack to support a variety of signaling applications. In this paper we present our study on the protocol overhead and performance aspects of GIST. We quantify network-layer protocol overhead and observe the effects of enhanced modularity and security in GIST. We developed a first open source GIST implementation at the University of Göttingen, and study its performance in a Linux testbed. A GIST node serving 45,000 signaling sessions is found to consume small amounts of CPU and memory (on average 1.1ms for processing a signaling message and 2.4KB memory for a session). Individual routines in the GIST code are instrumented to obtain a detailed profile of their contributions to the overall system processing. Important factors in determining performance, such as the number of sessions, state management, refresh frequency, timer management and signaling message size are further discussed. We investigate several mechanisms to improve GIST performance so as to be comparable with an RSVP implementation.
PDF [181.9 kB]
UML Profile for Communicating Systems ,
Dieter Hogrefe , Constantin Werner , Technical Report No. IFI-TB-2006-03, Institute for Informatics, University of Goettingen, Germany,
ISSN 1611-1044, March 2006.
Read abstract
This report presents a UML2 profile for communicating systems. It is driven by the experience of SDL and provides XMI based mapping from UML to SDL-2000 but it is not limited to SDL. It features language elements for high-level specification and description of Internet communication and signaling protocols where SDL is partly cumbersome. Due to its support of several concrete notations, this profile is aligned to work with most UML 2 compliant modeling tools. This report describes all stereotypes which are defined in this profile, gives an informal semantic description and proposes concrete notations.
Wirtschaftliche Erfolgspotenziale von WiMAX-Geschäftsmodellen in Deutschland ,
Dieter Hogrefe , André Riedel , Marco Zibull , Stephan Müller, Björn Ortelbach, Robert Schmaltz, Matthias Schumann, Multikonferenz Wirtschaftsinformatik 2006, Teilkonferenz Mobilität und Mobile Informationssysteme (MMS 2006),
February 2006.
Read abstract
Mit dem IEEE 802.16-2004 Standard, der auch als WiMAX (Worldwide Interoperability for Microwave Access) bezeichnet wird, kommt eine neue drahtlose Übertragungstechnologie auf den Markt, die die Lücke zwischen schmalbandigen, aber reichweitenstarken Mobilfunknetzen und schnellen in ihrer Reichweite, jedoch beschränkten Wireless Local Area Networks füllen kann. Es stellt sich die Frage, inwieweit der Einsatz dieser Technologie in Deutschland auch aus wirtschaftlicher Sicht erfolgreich gestaltet werden kann. Unter Beachtung der Spezifik des deutschen Breitbandmarktes werden in dieser Arbeit mögliche Geschäftsmodelle untersucht, die im deutschen Markt Erfolgspotenziale aufweisen. Die vorliegende Studie leistet einen Beitrag zur Einschätzung der Potenziale der WiMAX-Technologie in Deutschland und kann als Entscheidungshilfe bei der Strategieentwicklung für die im Wettbewerb stehenden TK-Unternehmen dienen.
Case study on the use of SDL for specifying IETF micro mobility ,
Dieter Hogrefe , Telemaco Melia , Rui Aguiar, Amardeo Sarma, COMSWARE 2006 International Conference on Communication Systems,
New Delhi, India, IEEE Communications Society, January 2006.
Read abstract
Recent protocols are become increasingly complex, and lead to further level of complexity when used in combination, often resulting in ambiguous behavior. This paper, starting from a case study, presents an improved approach to validate protocols in a tight loop, leading to faster and higher quality standards. The formal specifications can be used as supplementary material to resolve behavior that is ambiguous from only reading the standards, mostly specified in ASCII text. Further, it addresses how to validate the behavior of several protocols running together without the need for several independent implementations. The approach allows early validation using a large number of environmental triggers, including external unexpected behavior. Finally, useful guidelines are provided to allow easy development of such mobility environments by means of SDL tools.
PDF [180.4 kB]
A Review of Mobility Support Paradigms for the Internet ,
Xiaoming Fu , Dieter Hogrefe , Deguang Le , IEEE Communications Surveys and Tutorials, Volume 8, No. 1, First Quarter, pages 38-51,
IEEE, ISSN 1553-877X, 2006.
Read abstract
With the development of mobile communications and Internet technology, there is a strong need to provide connectivity for roaming devices to continuously communicate with other devices on the Internet ? at any time and anywhere. The key issue of this vision is how to support mobility in TCP/IP networks. In this paper, we review the TCP/IP protocol stack and analyze the problems associated with it in the mobile environment. We then investigate the mobility support techniques and existing solutions for providing mobility support on the Internet. We classify the proposed solutions based on the protocol layers and present paradigms for each category of layer. We also provide a comparison of the different solutions belonging to different categories, including their advantages and disadvantages. Results have shown that there is no single solution that perfectly addresses mobility support for the Internet. Finally, we conclude this survey with a recommendation of features that ought to be met in Internet mobility support.
PDF [235.5 kB]
2005
Formal Specification and Security Verification of the IDKE Protocol using FDR Model Checking ,
Dieter Hogrefe , Rene Soltwisch , Florian Tegeler, IEEE International Conference on Networks (ICON), Kuala Lumpur, Malaysia,
IEEE, November 2005.
Read abstract
The IDKE protocol is a mechanism aiming to provide authentication and session key establishment for mobile nodes after an inter domain handover. Credentials are forwarded from a previous access router to the new access router whereas initially no trust relationship exists. The IDKE protocol utilizes an IP based infrastructure to transfer a session-key due to mobile handover. In this paper, we give a formal specification of the IDKE protocol, its properties, pre- and post-conditions. Verification of security properties such as secrecy and authentication is performed by utilizing the model checker FDR. We optimize the specification, prove the capability, and figure out the limits of our optimized specification. We show that the IDKE protocol is capable to provide authenticated and secured key establishment. Furthermore we prove that the IDKE protocol also provides forward secrecy for the session key and for a secured tunnel in between two access routers.
Architectural Thoughts and Requirements Considerations on Video Streaming over the Internet ,
Xiaoming Fu , Dieter Hogrefe , Ingo Juchem , Jun Lei , Technical Report No. IFI?TB?2005?06, Institute for Informatics, University of Goettingen, Germany,
ISSN 1611?1044, November 2005.
Read abstract
With increasing demands of multimedia information over the Internet, video streaming has been received explosive attentions. With respect to the real-time nature of video streaming, instable bandwidth, latency, noise, packet loss, retransmission and out of order packet delivery are all problems that can affect video streaming over the Internet. However, the traditional Internet traffic is not sensitive to these problems. Based on the general video streaming architecture, we give out some considerations on design and architectural mechanisms, namely, media server, media compression, media QoS control, media distribution services, media security mechanisms and protocol stacks for video streaming. For each of these areas, we present some existing methods and implementations. Then we propose architecture via overlay multicast integrated with proxy caching to achieve efficiency, flexibility and scalability. Finally, we conclude this issue and point out the research direction.
PDF [503.1 kB]
NSIS: A New Extensible IP Signaling Protocol Suite ,
Xiaoming Fu , Dieter Hogrefe , Henning Schulzrinne, Attila Bader, Cornelia Kappler, Georgios Karagiannis, Hannes Tschofenig, and Sven Van den Bosch, IEEE Communications Magazine, Internet Technology Series, pages 133-141,
IEEE, October 2005.
Read abstract
In the last few years, a number of applications have emerged that can benefit from network-layer signaling, i.e., the installation, maintenance and removal of control state in network elements. These applications include path-coupled and path-decoupled quality of service (QoS) management and resource allocation, as well as network debugging, NAT and firewall control. These applications call for an extensible and securable signaling protocol. This paper discusses some of the recent standardization efforts in the IETF for a new extensible IP signaling protocol suite (NSIS). We describe the design of the NSIS protocol suite, and compare them with RSVP, the current Internet QoS signaling protocol.
PDF [159.9 kB]
Voice over Wireless LAN - A Fine-Scalable Channel-Adaptive Speech Coding Scheme ,
Dieter Hogrefe , André Riedel , Marco Zibull , to appear in Proceedings of The Third ACM International Workshop on Wireless Mobile Applications and Services on WLAN Hotspots (WMASH 2005), Cologne, Germany, ACM,
September 2005.
Read abstract
Achieving a fine-scalable and channel-adaptive speech coding scheme to provide reliable voice communication in wireless IP networks is an important challenge that opens new directions for research. In this proposal we review the problems and issues in supporting voice over wireless networks and examine the role of new speech coding techniques and the proper use of existing network protocols aimed at providing adequate quality of service in this difficult environment. We propose a new coding scheme, that fulfills the requirements of robust and reliable VoWLAN expectantly.
E2T: End-to-End Tunneling Extension to Mobile IPv6 ,
Xiaoming Fu , Dieter Hogrefe , Deguang Le , and Xiaoyuan Gu, Technical Report No. IFI-TB-2005-05, Institute for Informatics, University of Göttingen,
ISSN 1611-1044, September 2005.
Read abstract
In the standard Mobile IPv6, route optimization or bidirectional tunnelling through the home agent show inefficiency in per-packet forwarding, especially when both communicating endpoints are mobile. To be scalable and compatible, mobile devices? packets should be forwarded in a way with minimal changes to the network infrastructure. However, the current solutions do not provide any means for the end systems to perform optimized packet routing during the operation of mobile devices.
In this paper, following a performance analysis of Mobile IPv6 routing mechanisms, we present the E2T - an extension to Mobile IPv6 for routing packets. It reduces per-packet forwarding cost for the communications of mobile devices. With this approach, packets are routed thorough end-to-end tunnelling between communicating endpoints, which requires little change to Mobile IPv6, but allows more efficient forwarding behavior. The numerical analysis and simulation results show it requires less overhead than the standard route optimization and it helps to achieve a low end-to-end traffic delay.
PDF [323.6 kB]
Modeling Route Change in Soft State Signaling Protocols Using SDL: a Case of RSVP ,
Xiaoming Fu , Dieter Hogrefe , Constantin Werner , in A. Prinz, R. Reed and J. Reed (eds.), Proceedings of the 12th SDL Forum (SDL 2005), Grimstad, Norway, Lecture Notes in Computer Science, Volume 3530, pages 174-186,
Springer Verlag, ISBN 3-540-26612-7, June 2005.
Read abstract
Soft state signaling protocols install and maintain states in network nodes, expiring without receiving refreshes. These states require proper reparation when the flow path changes, especially in case of link or node failures. As the specifications usually do not describe in detail how to handle these failures, we present insights by developing SDL models for RSVP on this issue.
PDF [269.3 kB]
Video Image-based Intelligent Architecture for Human Motion Capture ,
Dieter Hogrefe , Jun Lei , Jiangrong Tan, ICGST International Journal on Graphics, Vision and Image Processing (GVIP),
Volume 5, May 2005.
Read abstract
The study of human motion is a fascinating subject in computer vision and has been developed quite a few years. Traditional methods to realize human motion capture mainly use equipments of machinery, electromagnetic, acoustics, optics, graphics and so on. Whereas these are some defects existed in these methods e.g. expensive equipments, the place limited by sensors and localization of sport range, and it has no consistent standards because of different purposes and requirements. Most importantly, they always need a person to execute the long and sterile work for surveillance. Sometimes only by manual operation cannot accord with desires that data should be collected without redundant or unhelpful information. In view of video characters which bring about changes and new opportunities in the human motion capturing technology, this paper presents an actual architecture to automatically capture human motion by comparing video images and extracting surveillant area. Then we provide an effective method for storage. Furthermore, the functionalities of architecture are realized in GOLF sport education example.
PDF [286.2 kB]
Modeling Soft State Protocols with SDL ,
Xiaoming Fu , Dieter Hogrefe , In: R. Boutaba et al. (Eds.), Proceedings of the 4th IFIP International Conference on Networking (Networking 2005), Waterloo, Canada, Lecture Notes in Computer Science, Volume 3462, pp. 289-302,
Springer Verlag, ISBN 3-540-25809-4, May 2005.
Read abstract
Soft state provides new services to packet-switching networks by introducing a type of state in the network nodes which is refreshed by periodical messages and otherwise expires. The operations of soft state protocols, which are being designed with ever greater complexity, need to be error-free and deadlock-free to avoid misusing network resources. Thus, verification, formal analysis and validation of these protocols become a vital task. In this paper we utilize formal techniques, specifically Specification and Description Language (SDL) and Message Sequence Charts (MSCs), for modeling, analysis and validation of various soft state protocols. We propose a general architecture for state management systems and find employing these techniques can help identify and correct possible design errors, which may be caused by informal specifications.
PDF [162.9 kB]
A Review of Mobility Support Paradigms for the Internet ,
Xiaoming Fu , Dieter Hogrefe , Deguang Le , Technical Report No. IFI-TB-2005-01, Institute for Informatics, University of Göttingen,
ISSN 1611-1044, January 2005.
Read abstract
With the development of mobile communication and Internet technology, there is a strong need to provide connectivity for roaming devices to communicate to other communication end points in the Internet at any time and anywhere. The key issue of this vision is how to support mobility in TCP/IP networks. In this paper, we review the TCP/IP protocol stack and analyze the problems associated with it in a mobile environment. We then investigate the mobility support techniques and existing solutions to provide mobility support in the Internet. We classify the proposed solutions based on the protocol layers and present examples for each category. We also provide a comparison of the different solutions belonging to different categories and in the same category, including their advantages and disadvantages, and conclude that there is no single solution perfectly addresses mobility support for the Internet.
PDF [347.0 kB]
Mobile Anwendungen - Eine interdisziplinäre Herausforderung ,
Dieter Hogrefe , André Riedel , Marco Zibull , Thomas Hess, Stefan Figge, Heidemarie Hanekop, Thomas Hess, Iris Hochstatter, Christian Kaspar, Barbara Rauscher, Markus Richter, WIRTSCHAFTSINFORMATIK 47 (2005) 1, 6-16,
January 2005.
Read abstract
Mobile data communication applications, referred to in this paper as mobile applications, were one of the technological innovation and investment targets in recent years. From the past it became obvious that mono-disciplinary approaches to investigate mobile applications have shortcomings when it comes to successful innovation and investment decisions as interdependencies are insufficiently addressed. The paper therefore aims at structuring the scientific contributions of computer science, business economics and sociology in the context of mobile applications to approximate a holistic understanding comprising technological feasibility, economic opportunities and human needs.
Telecommunications and UML Languages ,
Dieter Hogrefe , Reed, R., International Journal of Computer and Telecommunications Networking,
Elsevier, 2005.
2004
A Method for Authentication and Key Exchange for Seamless Inter-Domain Handovers ,
Xiaoming Fu , Dieter Hogrefe , Rene Soltwisch , and Sathya Narayanan, Proceedings of 12th IEEE International Conference on Networks (ICON 2004), Singapore, pp. 463-469,
ISBN 0-7803-8783-X, November 2004.
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With the rapid growth of the Internet and mobile wireless technologies, an ever-increasing requirement on securing services between mobile users and access networks has become especially important. When a user roams into a foreign network, in addition to data confidentiality, mutual authentication between the user and the provider is also a vital issue. These concerns and the desire to stay seamlessly connected lead to the demand of fast authentication and key establishment mechanisms, which are particularly difficult in inter-domain handover scenarios. In this paper, we introduce a novel mechanism to provide a simple but effective method, which forwards the key from the previous access router to the new access router that the mobile node attaches to. With this mechanism, trust relationship can be re-established even if the access routers do not trust each other in such an inter-domain scenario. Compared with the classical authentication method us
