Publications
2009
Overhead and Performance Study of the General Internet Signaling Transport (GIST) Protocol ,
Xiaoming Fu , Dieter Hogrefe , Henning Schulzrinne, Hannes Tschofenig, and Christian Dickmann, ACM/IEEE Transactions on Networking, 17(1): 158-171,
February 2009.
2008
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, 2008.
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]
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]
General Internet Signaling Transport (GIST) over SCTP ,
Xiaoming Fu , Christian Dickmann, and Jon Crowcroft, Internet Engineering Task Force, Next Steps in Signaling (NSIS) Working Group,
March 2007.
Read abstract
The General Internet Signaling Transport (GIST) protocol currently uses TCP or TLS over TCP for connection mode operation. This document describes the usage of GIST over the Stream Control Transmission Protocol (SCTP). The use of SCTP can take the advantage of features provided by SCTP, namely streaming-based transport, support of multiple streams to avoid head of line blocking, and the support of multi-homing to provide network level fault tolerance. Additionally, the support for the Partial Reliability Extension of SCTP is discussed.
PDF [19.9 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]
From Resource Reservation to Extensible IP Signaling ,
Xiaoming Fu , Habilitation Thesis, Mathematische Fakultaet, Universitaet Goettingen, Goettingen, Germany,
October 2006.
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]
Securing the Next Steps in Signalling (NSIS) Protocol Suite ,
Xiaoming Fu , and Hannes Tschofenig, International Journal of Internet Protocol Technology, Volume 1, No. 4, pages 271-282,
InderScience Publishers, ISSN 1743-8209, August 2006.
Read abstract
The Next Steps In Signalling (NSIS) protocol suite represents an extensible framework for enabling various signalling applications over IP-based networks. The framework consists of two layers that need different types of security protection; the lower layer mainly deals with the discovery of adjacent peers and establishment of channel security to protect the delivery of signalling messages between two peers, while the upper layer provides the signalling application specific functionalities. Different security properties are required at the two layers with stronger authorisation functionality at the signalling application layer. In this paper we examine how various security vulnerabilities can be utilised by an adversary, including eavesdropping, Man-In-The-Middle (MITM) attacks, fraud and Denial of Service (DoS) attacks. Moreover, we describe how to protect against a number of selected security threats and highlight some security challenges that require further research.
PDF [431.5 kB]
Implementation and Performance Study of a New NAT/Firewall Signaling Protocol ,
Xiaoming Fu , Niklas Steinleitner , Henning Peters, and Hannes Tschofenig, in Proceedings of the 26th International Conference on Distributed Computing Systems-Workshops (ICDCSW 2006), the 5th International Workshop on Assurance in Distributed Systems and Networks (ADSN2006), Lisboa, Portugal,
IEEE Computer Society, ISBN 0-7695-2541-5, July 2006.
Read abstract
The NAT/Firewall NSIS Signaling Layer Protocol (NAT/FW NSLP) is a path-coupled signaling protocol for explicit Network Address Translator and firewall configuration within an extensible IP signaling framework currently being developed by the IETF Next Steps in Signaling (NSIS) working group. This new protocol allows end hosts to signal along a path to configure NATs and firewalls according to the data flow needs. In this paper we present a first open source implementation and performance evaluation of the NAT/FW NSLP protocol. The implementation utilizes a generic state machine template and can automatically generate source code for message handling classes. The performance study shows that our implementation scales well and is able to support firewall signaling for up to tens of thousands of flows in parallel even in a low-end PC testbed environment. The overall performance bottleneck is found to lie in the utilized firewall implementation, not depending on the NAT/FW NSLP implementation.
PDF [394.6 kB]
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]
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.
GONE: an Infrastructure Overlay for Resilient, DoS-Limiting Networking ,
Xiaoming Fu , and Jon Crowcroft, Proceedings of the 16th ACM International Workshop on Network and Operating Systems Support for Digital Audio and Video (NOSSDAV 2006), Newport, Rhode Island, USA,
ACM, May 2006.
Read abstract
With today's penetration in volume and variety of information flowing across the Internet, data and services are experiencing various issues with the TCP/IP infrastructure, most notably availability, reliability and mobility. Therefore, a critical infrastructure is highly desireable, in particular for multimedia streaming applications. So far the proposed approaches have focused on applying application-layer routing and path monitoring for reliability and on enforcing stateful packet filters in hosts or network to protect against Denial of Service (DoS) attacks. Each of them solves its own aspect of the problem, trading scalability for availability and reliability among a relatively small set of nodes, yet there is no single overall solution available which addresses these issues in a large scale.
We propose an alternative overlay network architecture by introducing a set of generic functions in network edges and end hosts. We conjecture that the network edge constitutes a major source of DoS, resilience and mobility issues to the network, and propose a new solution to this problem, namely the General Internet Signaling Transport (GIST) Overlay Networking Extension, or GONE. The basic idea of GONE is to create a half-permanent overlay mesh consisting of GONE-enabled edge routers, which employs capability-based DoS prevention and forwards end-to-end user traffic using the GIST messaging associations. GONE's use of GIST on top of SCTP allows multi-homing, multi-streaming and partial reliability, while only a limited overhead for maintaining the messaging association is introduced. In addition, upon the services provided by GONE overlays, hosts are identified by their unique host identities independent of their topologies location, and simply require (de-) multiplexing instead of the traditional connection management and other complex functionality in the transport layer. As a result, this approach offers a number of advantages for upper layer end-to-end applications, including intrinsic provisioning of resilience and DoS prevention in a dynamic and nomadic environment.
PDF [283.3 kB]
Comparison Studies between Pre-Shared and Public Key Exchange Mechanisms for Transport Layer Security ,
Xiaoming Fu , Fang-Chun Kuo , Hannes Tschofenig, and Fabian Meyer, Proceedings of the 9th IEEE Global Internet Symposium, in conjunction with IEEE INFOCOM 2006, Barcelona, Spain, pages 77-82,
IEEE, ISBN 3-937201-01-7, April 2006.
Read abstract
The pre-shared key based mechanisms for Transport Layer Security (TLS) were recently standardized by the IETF to extend the set of ciphersuites by utilizing existing key management infrastructures. The benefit of pre shared based mechanisms is the avoidance or reduction of the cryptographic operations used in public-key based mechanisms. However, so far there are no performance measurements for pre-shared key based ciphersuites available. In this paper, we present a systematic analysis and performance comparison between the pre-shared key exchange mechanisms and the standard public key exchange mechanisms in TLS. Our performance metrics are processing
time and transmitted amount of data for a handshake establishment. Furthermore, the interaction between the overall TLS handshake duration and the network environment is evaluated. The results for different key exchange mechanisms are comparatively studied and the design choices of pre-shared key based key exchange mechanisms have been validated. Experimental results give details about the performance improvement of the preshared key based mechanisms compared to the standard public key based mechanisms.
PDF [331.4 kB]
Comparison Studies between Pre-Shared Key and Public Key Exchange Mechanisms for Transport Layer Security (TLS) ,
Xiaoming Fu , Fang-Chun Kuo , Hannes Tschofenig, and Fabian Meyer, Technical Report No. IFI-TB-2006-01, Institute for Informatics, University of Göttingen, Göttingen, Germany,
ISSN 1611-1044, January 2006.
Read abstract
The public-key based handshake process of TLS is regarded as part of bottleneck that significantly degrades the performance. The pre-shared key based key exchange mechanisms for TLS were recently standardized by the IETF for avoiding or reducing the cryptographic operations in public-key based mechanisms. However, so far there is no performance measurement for pre-shared key based key exchange suites available. In this paper, we present a systematic analysis of performance comparison between the pre-shared key exchange mechanisms and the standard public key exchange mechanisms in TLS. Our performance metrics are the processing time in both slow and fast processor machines as well as the transmitted data amount for a handshake establishment. Furthermore, the interaction of the overall TLS handshake duration and the network environment is evaluated. The results for different key exchange mechanisms are comparatively studied and the design choices of pre-shared key based key exchange mechanisms have been validated. It has been observed that pre-shared key based mechanisms perform better than the standard public key based mechanisms.
PDF [357.6 kB]
Principles and Experiments of Explicit Delay Control ,
Xiaoming Fu , Xiaoyuan Gu, Dirk Markwardt, and Lars Wolf, Proceedings of IEEE Consumer Communications and Networking Conference (CCNC'06), Las Vegas, USA,
IEEE, January 2006.
Read abstract
Real-time interactive multimedia applications are highly delay-sensitive, and packets that are out of delay boundaries are usually obsolete. However the current Internet Protocol lacks a way to control the lifetime of the packets explicitly. We propose a packet lifetime control mechanism called Explicit Delay Control (EDC) that embeds a Maximum Tolerable Delay (MTD) field in an IPv4 option. At each network node, the MTD is deducted by the singlehop delay. Packets that expire their lifetime are discarded and non-congestion related delay losses are signaled to the sender to reduce inaccuracy in delay estimations and to adapt to path changes. We implemented EDC in the Linux kernel. Our evaluation has shown that EDC is an effective scheme to ensure the ?legality? of the packets, reduce the waste of bandwidth and processing time in the networks, and alleviate congestions.
PDF [207.6 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
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]
A Quality-of-Service Resource Allocation Client for CASP ,
Xiaoming Fu , Henning Schulzrinne, Hannes Tschofenig, and Jochen Eisl, Technical Report No. TB-IFI-2005-07, Institute for Informatics, University of Goettingen, Germany,
ISSN 1611-1044, November 2005.
Read abstract
Signaling resource reservations is one of the possible applications of the Cross-Application Signaling Protocol (CASP). This document describes a client protocol that supports per-flow resource reservationin both sender- and receiver-directed modes operation.
PDF [99.8 kB]
Security Implications of the Session Identifier ,
Xiaoming Fu , Hannes Tschofenig, Henning Schulzrinne, Robert Hancock, and Andrew McDonald, Technical Report No. TB-IFI-2005-08, Institute for Informatics, University of Goettingen, Germany,
ISSN 1611-1044, November 2005.
Read abstract
As one result of the analysis activities in the NSIS group it was realized that mobility and the ability to change the flow identifier causes problems with existing QoS reservations. To be able to associate a signaling message with existing state an identifier other than the flow identifier had to be used. Such an abstraction is achieved with the session identifier which allows identification of established state independently of the flow characteristics.
Although the introduction of a session identifier sounds simple and beneficial, it introduces a problem which is subsequently referred to as the session ownership problem.
This document describes the session ownership problem, the implications for an NSIS protocol and summarizes already discussed solutions.
PDF [79.7 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]
Towards Self-optimizing Protocol Stack for Autonomic Communication: Initial Experience ,
Xiaoming Fu , Xiaoyuan Gu, Hannes Tschofenig, and Lars Wolf, In: Ioannis Stavrakakis and Michael Smirnov (eds), Proceedings of 2nd IFIP International Workshop on Autonomic Communication (WAC 2005), Athens, Greece, Lecture Notes in Computer Science, Volume 3854, pages 186-201,
Springer-Verlag, October 2005.
Read abstract
The Internet is facing ever-increasing complexity in the construction, configuration and management of heterogeneous networks. New communication paradigms are undermining its original design principles. The mobile Internet demands a level of optimum that is hard to achieve with a strictly-layered protocol stack. Questioning if layering is still an adequate foundation for autonomic protocol stack design, we study the state-of-the-art from both the layered camp and its counterpart. We then outline our vision on protocol stack design for autonomic communication with the POEM model and its internals. A novel cross-layer design approach that combines the advantages of layering and the benefits of holistic and systematic cross-layer optimization is at the core of this work. With inspirations from the natural ecosystem, we are working on the role-based Composable Functional System for self-optimization that features proactive monitoring and control. By doing so step-by-step, we envisage reaching the goal of self-tuning autonomic network with high level of autonomy and efficiency, with minimum human management complexity and user intervention.
PDF [296.8 kB]
Fast Seamless Handover Scheme and Cost Performance Optimization for Ping-Pong Type of Movement ,
Xiaoming Fu , Zongkai Yang, Yuming Wang, Dasheng Zhao, and Jianhua He, Proceedings of the 16th Annual IEEE International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC 2005), Berlin, Germany,
IEEE, September 2005.
Read abstract
The ping-pong type of movement is a typical motion manner in mobile IPv6 networks, which will bring frequent handovers and thus increase signaling burden. On the other hand, reducing handover delay in this case seems to be more significant. In this paper we propose a fast seamless handover scheme for the ping-pong type of movement as an extension to the hierarchical mobile IPv6. Based on the simulation results, it can be observed that, by setting the reservation active flag (RAF) and the offline count down timer (CDT), the scheme significantly reduces QoS signaling cost and handover delay. Furthermore, the simulations work out an optimized CDT for acquiring better cost performance of resource reservation.
PDF [286.8 kB]
Advanced Authentication and Authorization for Quality of Service Signaling ,
Xiaoming Fu , Tseno Tsenov, Hannes Tschofenig, and Eckhart Koerner, 1st IEEE/CreatNet Workshop on Security and QoS in Communication Networks (SecQoS 2005), Athens, Greece (in conjunction with the first IEEE International Conference on Security and Privacy for Emerging Areas in Communication and Networks - SECURECOM 2005),
IEEE Computer Society Press, September 2005.
Read abstract
One of the key requirements of today?s and future network infrastructures is to provide Quality of Service (QoS) support for end-to-end applications, by distinguishing the application flows and properly handling them in network nodes. As an important component to achieve Internet QoS, explicit signaling schemes for resource reservation have been proposed, which deal with admission, installation and refreshment of QoS reservation state information. To be useful, any QoS signaling protocol should provide a capability for authentication and authorization of the QoS requests, especially in environments where the end points are not trusted by the network nodes. However, existing protocols for QoS signaling encounter a number of authentication and authorization issues, which limit their application scenarios. The advent of NSIS QoS Signaling Layer Protocol (QoS-NSLP) offers the prospect to overcome some of these issues. After describing the overall design of QoSNSLP, we present an approach to support advanced authentication and authorization capabilities by using the Extensible Authentication Protocol (EAP). In comparison with existing approaches, this approach, combined with the support for effective interaction with the Authentication, Authorization and Accounting (AAA) infrastructure, provides flexible and extensible authentication and authorization methods for the QoS signaling.
PDF [959.2 kB]
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]
Enabling Mobile IPv6 in Operational Environments ,
Xiaoming Fu , Hannes Tschofenig, Srinath Thiruvengadam, and Wenbing Yao, in: Pascal Lorenz (ed), Proceedings of the 10th IFIP International Conference on Personal Wireless Communications (PWC 2005), Colmar, France, pp. 365-372,
Imperial College Press, ISBN 1-86094-582-1, August 2005.
Read abstract
Although Mobile IPv6 allows maintaining transport layer connections alive when an IPv6 node roams to different access networks, certain enabling mechanisms are needed for it to work in large scale network scenarios, including, most notably, issues with Mobile IPv6 bootstrapping and firewall traversal. This paper tries to address these problems by extending the IETF PANA and NSIS protocols to form an extensible framework for wide deployment of a secure, light-weight mobility service in operational IPv6 environments.
PDF [162.4 kB]
RSVP Standards Today and the Path Towards a Generic Messenger ,
Xiaoming Fu , Jukka Manner, In: H. de Meer and N. Bhatti (eds.), Proceedings of the 13th International Workshop on Quality of Service (IWQoS 2005), Passau, Germany, Lecture Notes in Computer Science, Volume 3552,
Springer Verlag, ISBN 3-540-26294-6, June 2005.
Read abstract
RSVP is a very well-known protocol to support resource reservations in IP-based networks. This paper provides a preliminary inventory of RSVP standards and discusses the path towards a generic messenger for Internet signaling.
PDF [62.4 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]
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]
Analysis of Existing Quality-of-Service Signaling Protocols ,
Xiaoming Fu , and Jukka Manner, Request for Comment (RFC) 4094,
Internet Engineering Task Force, May 2005.
Read abstract
This document reviews some of the existing Quality of Service (QoS) signaling protocols for an IP network. The goal here is to learn from them and to avoid common misconceptions. Further, we need to avoid mistakes during the design and implementation of any new protocol in this area.
PDF [68.0 kB]
Performance Analysis of the TCP/IP Stack of Linux Kernel 2.6.9 ,
Xiaoming Fu , Niklas Steinleitner , Jan Demter, Christian Dickmann, and Henning Peters, Technical Report No. IFI-TB-2005-03, Institute for Informatics, University of Göttingen, Germany,
ISSN 1611-1044, April 2005.
Read abstract
This document reports the project "performance study of the TCP/IP stack for the Linux kernel" which we performed during the practical course Computer Networks in winter semester 2004/05, including its design, implementation and performance results. We analysed the packet processing time traversing each layer of the Linux kernel 2.6.9 TCP/IP stack (socket, TCP/UDP, IP and Ethernet) and the influence of multi-threading and different packet sizes. The design is based on the idea of inserting probing points via hooks in the kernel code and export timing data to a userspace application. A packet generator and analysis tools were also developed. The results demonstrate a number of key concepts in TCP/IP networking, such as layering, user-system interface, connection versus datagram modes, processing routines and their overhead in different layers. Some preliminary results reveal the system has its bottlenecks in different situations, and our tools released under GPL-license have been designed in such a way that allows easy extensibility for other networking diagnostics purposes.
PDF [246.1 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]
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 used in GSM and a recently proposed EAP-based secure key exchange protocol, our approach shows advantages of faster key exchange and authentication with only minimal message exchange in the wireless link.
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QoS and Security in 4G Networks ,
Xiaoming Fu , Dieter Hogrefe , Rene Soltwisch , and Sathya Narayanan, Proceedings of the 1st CIC/IEEE Global Mobile Congress (GMC 2004), Shanghai, China, pp. 117-122,
October 2004.
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Future 4G mobile communication networks are expected to provide all IP-based services for heterogeneous wireless access technologies, assisted by mobile IP to provide seamless Internet access for mobile users. Two major challenges in developing such heterogeneous network infrastructure are QoS provisioning and security services for mobile users? communication flows. This paper proposes a new architectural view and methodologies for QoS and security support in 4G networks, which integrates QoS signaling with authentication, authorization and accounting (AAA) services to both guarantee the user applications? QoS requirements and achieve efficient authentication, authorization and key exchange.
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Implementation and Evaluation of the Cross-Application Signaling Protocol (CASP) ,
Xiaoming Fu , Dieter Hogrefe , and Sebastian Willert, Proceedings of the 12th IEEE International Conference on Network Protocols (ICNP 2004), Berlin, Germany, pp. 61-71,
IEEE Computer Society Press, ISBN 0-7695-2161-4, October 2004.
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In this paper, we describe implementation aspects and performance results of a novel general signaling protocol for the Internet, the Cross-Application Signaling Protocol (CASP). There has been much debate on the applicability of RSVP as a general signaling protocol for the Internet, particularly with respect to its modularity, complexity, security and mobility support. Based on a layered architecture, the CASP design intends to address these challenges, which, unlike RSVP, provides a simpler mechanism for reliability and security by re-using existing protocols for transporting signaling messages. In addition, it supports a wide range of signaling applications. While this concept is considered to be advantageous over RSVP signaling, the actual mechanisms and behaviors of the CASP implementation have not yet been explored. Our study attempts to shed light on this issue by presenting a first public CASP implementation and preliminary examination of its properties. Performance results show and analyze the round trip times and their variances of signaling messages upon different number of signaling requests and different congestion situations in the experimental setup. The memory required for a large number of signaling sessions and the CPU consumption for each routine from profiling the implementation are low. Although further work is necessary, critical design choices in CASP have been proven useful and practically feasible.
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Modeling Soft State Protocols with SDL ,
Xiaoming Fu , Dieter Hogrefe , Technical Report No. IFI-TB-2004-02, Institute for Informatics, University of Göttingen, Germany,
ISSN 1611-1044, August 2004.
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Soft state enables new services to packet-switching networks by introducing a type of state in the network nodes which is refreshed by periodical messages otherwise expire. System designers build protocols that implement soft state concepts based on intuition or on high-level explanations believe that the design is "better" than hard state and soft state implementations should be robust, reliable and interoperable. As states in the network nodes are critical for both applications the and network infrastructure, the operations of soft state protocols, which tend to be designed more and more complex, need to be error-free and deadlock-free. 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 Chart (MSC), for modeling, analysis and validation of general soft state protocols. We propose a general architecture of state management systems and find several points through the SDL/MSC modeling which may enrich the design, modeling and evaluation of real soft state protocols: 1) modeling these protocols using these techniques is feasible, 2) it can be possible to use these techniques to identify possible design errors and deadlocks/livelocks, which may be caused by imprecise informal specifications of these protocols.
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Implementation and Evaluation of the Cross-Application Signaling Protocol (CASP) ,
Xiaoming Fu , Dieter Hogrefe , and Sebastian Willert, Technical Report No. IFI-TB-2004-001, Institute for Informatics, University of Göttingen, Germany,
ISSN 1611-1044, April 2004.
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In this report, we describe implementation aspects and performance results of a novel general signaling protocol for the Internet, the Cross-Application Signaling Protocol CASP). Much debate exists about the applicability of RSVP as a general signaling protocol in the Internet, particularly for its modularity, complexity, security and mobility support. Based on a layered architecture, the CASP design intends to address these challenges and unlike RSVP, it provides a simpler mechanism for reliability and security by re-using existing protocols for transporting signaling messages, and supports a wide range of signaling applications. While this concept is considered to be advantageous over RSVP signaling, the actual mechanisms and behaviors of the CASP implementation have not yet been explored. With our work, despite being still far from a final judgment, we try to shed light on this issue by presenting a first public CASP implementation and a preliminary study about its properties. Performance results show that even under heavy signaling loads, the round trip time of signaling messages is acceptable (appr. 5ms in serving more than 1000 simultaneous signaling client applications in the initiator each at a random refresh interval between 3s and 15s in our experiments), and the memory and CPU consumption of the implementation are low. Although further work will be necessary, critical design choices in CASP have been proved to be feasible.
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2003
Secure, QoS-Enabled Mobility Support in IP-based Networks ,
Xiaoming Fu , Tianwei Chen, Andreas Festag, Holger Karl, Günter Schäfer, and Changpeng Fan, Proceedings of the 4th Annual IP-based Cellular Network Conference (IPCN 2003), Paris, France,
December 2003.
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The rising number of mobile users, the advent of various radio access technologies, and the increasing importance of IP services over wireless as well as wired networks pose a number of new challenges. While Mobile IP has been designed for mobility management in IP networks, it may result in high latency and signaling overhead during handoff. Thus, advanced mobility mechanisms improving Mobile IP are desired to perform efficient handoffs. Also, appropriate Quality-of-Service (QoS) support is needed for mobility-enhanced IP in order to meet end users? expectations. Furthermore, security measures are required to protect the network infrastructure.
This paper describes the Secure, QoS-enabled Mobility (SeQoMo) architecture addressing these issues. In particular, optimization of handoff operations, low latency QoS re-establishment for IP-level handoff, authentication, and QoS-aware authorization for mobile nodes are investigated and integrated in a unified framework. We also describe how the SeQoMo architecture as a whole supports efficient handoff processing especially during local movements, with optimized QoS support and authentication and QoS-aware authorization services.
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Prototype Implementation and Performance Evaluation of a QoS-Conditionalized Handoff Scheme for Mobile IPv6 Networks ,
Xiaoming Fu , Axel Neumann, and Holger Karl, Proceedings of the 18th Annual IEEE Computer Communications Workshop (CCW 2003), California, USA, pp. 24-29,
IEEE Press, ISBN 0-7803-8239-0, October 2003.
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Future internetworks will include large numbers of portable devices moving among small, wireless cells. In order to support real-time applications, users demand seamless mobility and Quality-of-Service (QoS)provisioning. One approach towards a more flexible, customizable and scalable mobility architecture that also reduces signaling load and handoff latency results from the introduction of micro-mobility. Furthermore, by coupling QoS signaling and mobility management, QoS requirements can be negotiated without incurring significant additional signaling latency.
This paper presents the prototype implementation and performance evaluation of such a QoS-enabled micro-mobility scheme, which is called "QoS-conditionalized handoff". We extended the Mobile IPv6 for Linux implementation to support the basic mode of Hierarchical Mobile IPv6 as the underlying micro-mobility mechanism. One problem that appeared during the implementation was the rather complex event handling in the mobile node; to enable a simple and generic way of event handling, a priority-based execution structure has been developed that can be easily adapted to various policies.
Our experimental results show that by this QoS-conditionalized handoff scheme, QoS-enabled handoffs can be achieved with a small amount of introduced latency compared to Hierarchical Mobile IPv6, which is much less than that of Mobile IPv6. It is further observed that fewer packets were lost and registration latency could be much more decreased when mobility management in the mobile node takes advantage of a movement detection mechanism to expedite the QoS-conditionalized handoff procedure.
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Development of QoS Signaling Protocols in the Internet ,
Xiaoming Fu , Proceedings of the 28th Annual IEEE Conferfence on Local Computer Networks (LCN 2003), Bonn/Königswinter, Germany, pp. 636-637, Workshop on High-Speed Local Networks,
IEEE Computer Society Press, ISBN 0-7695-2037-5, October 2003.
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QoS signaling protocol is one of the key components in Internet QoS architectures to establish, maintain, and remove reservation states in network nodes. This paper gives an overview of the recent efforts underway on next steps in QoS signaling protocols, namely RSVP extensions with mobility support, QoS-conditionalized handoff protocol, the layered architecture RSVP Lite and the Cross-Application Signaling Protocol (CASP). These efforts address main issues with existing approaches differently : modularity, complexity and mobility support, with a focus on protocol behaviors based on different design principles. The paper also provides pointers to standards effort towards general Internet signaling and other service-specific signaling protocols.
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Mobility Support for Next-Generation Internet Signaling Protocols ,
Xiaoming Fu , Henning Schulzrinne, and Hannes Tschofenig, Proceedings of the IEEE 58th Vehicular Technology Conference (VTC 2003-Fall), Orlando, Florida, USA, pp. 1979-1983, Symposium on IP Mobility,
IEEE, ISBN 0-7803-7954-3, October 2003.
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Internet signaling protocols establish, maintain and remove state along the data path. Next-generation signaling protocols design must meet the scaling requirements imposed by the various tasks of the Internet signaling applications, such as resource reservation and middlebox configuration, and to meet the demand for general functionality in signaling protocols, including strong security, reliability, congestion control, support for various signaling purposes and message sizes, and efficient support for mobility. This paper presents a generic signaling architecture, the Cross-Application Signaling Protocol (CASP) and describes how it supports efficient and secure signaling in IP mobility scenarios. In this approach, the signaling functionality is splitted into two layers: a generic messaging layer which provides the generic functionality for message delivery, and a client layer consisting of a next-hop discovery client and any number of client protocols which perform the actual signaling tasks. The essential mechanisms required to support mobility are: (1) a session identifier uniquely selected by the initiator and effective discovery of the cross-over node; (2) a branch identifier incrementally assigned for the new branch and efficient release of state in the abandoned branch; (3) ensuring discovery messages are delivered exactly following the path that mobile IP packets are encapsulated; (4) effective hop-by-hop authentication and reauthorization provided by the messaging layer, non hop-by-hop security for signaling clients and denial-of-service protection in the discovery client.
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CASP ? Cross-Application Signaling Protocol ,
Xiaoming Fu , Henning Schulzrinne, Hannes Tschonfenig, and Andrew McDonald, Technische Berichte des Instituts für Informatik an der Georg-August-Universität Göttingen,
Institut für Informatik, Georg-August-Universität Göttingen, Germany, ISSN 1611-1044, IFI-TB-2003-01, (equivalent to the Internet draft ?CASP ? Cross-Application Signaling Protocol?, draft-schulzrinne-nsis-casp-01), March 2003.
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CASP is a modular potocol for establishing network control state along a data path between two nodes communicating on the Internet.
The signalling problem addressed by CASP is the same as the overall problem being addressed by the NSIS activities.
The CASP framework is defined as a modular protocol, which includes a general purpose messaging layer (M-layer), which supports a number of client layers for particular ignalling applications (e.g. QoS, MIDCOM). In addition there is distinct, special purpose client component for next-peer discovery.
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Towards RSVP Lite: Light-weight RSVP for Generic Signaling ,
Xiaoming Fu , Cornelia Kappler, Proceedings of the 17th International Conferfence on Advanced Information Networking and Applications, Xi'an, China, pp. 619-622,
IEEE Computer Society Press, ISBN 0-7695-1906-7, March 2003.
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RSVP is a reservation setup protocol designed specifically to support QoS signaling in the Internet. However, RSVP end-to-end signaled QoS for the Internet has not become a reality. Moreover, there are many other applications demanding different signaling services. This paper analyses the features of RSVP version 1 we believe to be essential, and its complexity due to QoS-oriented design and multicast support as an indispensable component in a signaling protocol, deriving the design principles to be covered in a more generic signaling protocol. Based on this analysis, we present a light-weight version of RSVP, RSVP Lite, which clearly separates the signaled data from signaling messages and removes the multicast capability from the mandatory components of RSVP. RSVP Lite is intended to be applicable to a wide range of networking environments, while providing the flexibility to serve for generic signaling purposes and incremental deployment in the Internet.
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Design of CASP ? a Technology Independent Lightweight Signaling Protocol ,
Xiaoming Fu , Henning Schulzrinne, Cornel Pampu, and Cornelia Kappler, Proceedings of the 1st International Workshop on Inter-domain Performance and Simulation (IPS 2003), Salzburg, Austria,
February 2003.
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Existing signaling solutions are insufficient in terms of inter-domain and out-of-path signaling, mobility support and inter-working with policy and security mechanisms. The paper presents the Cross-Application Signaling Protocol (CASP) which is a general-purpose protocol for managing state information in network devices. This technology independent signaling protocol can be used for inter- and intra-domain QoS signaling, the configuration of middleboxes, for collecting measurement data and any other application where state management is required. It relies on existing transport protocols and consists of a messaging layer and a client layer. The messaging layer is application independent and is responsible for routing, session establishment and feature negotiation. In contrast to this application independent component of CASP, the client layer is the application-dependent part. As an example for a client the paper describes the QoS Resource Allocation Client for CASP and discusses requirements for extending CASP to include interdomain signaling. The discovery of next peers along the data path is handled by the Scout protocol, which is a specialized client protocol. Some of the basic mechanisms are derived from existing protocols. This way the design of this protocol relies on the experiences made in this area and is therefore one of the promising protocol candidates for the IETF NSIS WG.
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2002
Analysis on RSVP Regarding Multicast ,
Xiaoming Fu , Cornelia Kappler, and Hannes Tschofenig, Technische Berichte des Instituts für Informatik an der Georg-August-Universität Göttingen,
Institut für Informatik, Georg-August-Universität Göttingen, Germany, ISSN 1611-1044, IFI-TB-2002-001, October 2002.
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RSVP version 1 has been designed for optimum support multicast. However, in reality multicast is being used much less frequently than anticipated. Still, even for unicast (one sender, one receiver) full-fledged multicast-enabled RSVP signaling must be used. As pointed out in the NSIS requirement draft, multicast would not be necessarily required for an NSIS signaling protocol. This draft analyses ingredients of RSVP Version 1 which are affected by multicast, and derives how these ingredients may look like if multicast is not supported in the generic RSVP signaling protocol and adapt related functionalities accordingly - we call the resulting feature set "RSVP Lite", a potentially more light-weight version of RSVP.
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QoS-Conditionalized Handoff for Mobile IPv6 ,
Xiaoming Fu , Holger Karl, and Cornelia Kappler, Proceedings of the 2nd IFIP International Networking Conference (NETWORKING 2002), Pisa, Italy, Lecture Notes in Computer Science, Volume 2345, pp.721-730,
Springer Verlag, ISBN 3-540-43709-6, May 2002.
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In this paper we present a scheme that enables a mobile user to perform a "QoS-conditionalized" handoff when moving to an overlapping area in Mobile IPv6. The idea is to use a QoS hop-by-hop option piggybacked in the binding messages for QoS signaling and conditionalize a handoff upon the availability of sufficient resources along the new transmission path. Our scheme builds upon the hierarchical mobile IPv6 protocol and is especially suited for micro-mobility. It also enables the mobile node to flexibly choose among a set of available access points so that the mobile node can transmit packets through a route which offers satisfying QoS.
PDF [110.4 kB]
2001
PRM: A Resource Management Framework for Policy-driven QoS Control in Enhanced Internets ,
Xiaoming Fu , and Yaoxue Zhang, Chinese Journal of Electronics, 10(1): 13-18,
ISSN 1022-4653, October 2001.
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The Internet has evolved from a traditional best-effort delivery data network into an enhanced Internet that can provide a certain Quality of Service (QoS) mechanisms for applications. However, these QoS mechanisms usually do not take policy factors into account such as priority and time-of-day. The paper presents a Resource Management Framework for Policy-driven QoS control (PRM) in enhanced internets, which consists of four components: Domain Policy Controller (DPC) resides an administrator domain, Border Resource Manager (BRM) resides between adjacent domains, Interior Resource Manager (IRM) in each router between two BRMs within the same domain, and End-system Resource Manager (ERM) in charge of end-node/host router resources. We first introduce challenges and demands facing the enhanced internets, then give a formalized definition of policy and describe the functions and interaction of components of PRM. Specifically we take QoS-pricing policy used in a DiffServ environment as an example to illustrate the operational phases of PRM.
PDF [99.9 kB]
