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2009
What Level of Estimating Accuracy Does TCP Need and Can TCP Achieve ,
Lin Cong, Guohan Lu, Yang Chen , Beixing Deng, Xing Li, Poster session of the 5th ACM International Conference on emerging Networking EXperiments and Technologies (CoNEXT 2009), Rome, Italy,
December 2009.
A System for Peer-to-Peer Video Streaming in Resource Constrained Mobile Environments ,
Martin Stiemerling , Sebastian Kiesel, U-NET CoNext 2009 workshop,
ACM, December 2009.
Zusammenfassung lesen
Peer-to-Peer based near-live video streaming is becoming more and more popular with users of xed-line broadband network access, but it is mostly unavailable to mobile users, as cellular networks, such as GPRS/UMTS, cannot meet the bitrate requirements, while other wireless technologies, such as WLAN, may be fast enough but cover only very limited areas. However, there is a small but important set of scenarios, where several mobile users in close physical proximity are interested in retrieving the same content. We propose a P2P-TV system that enables them to retrieve video chunks in a cooperative way. The coordinated and efficient usage of all wireless resources available to a group of mobile hosts is the key to enable P2P-TV in mobile environments. This paper introduces our general concept. Simulation based studies are presented to assess dierent resource allocation strategies and to demonstrate the feasibility of our approach for delivering near-live TV in resource constrained mobile environments.
Pre-Congestion Notification based Flow Management in MPLS-based DiffServ Networks ,
Mayutan Arumaithurai , Ruediger Geib, Rene Rex , and Xiaoming Fu , The 28th IEEE International Performance Computing and Communications Conference (IPCCC 2009), Phoenix, AZ, USA,
IEEE, December 2009.
End-to-End Versus Hop-by-Hop Soft State Refresh for Multi-hop Signaling Systems ,
Jianhua He, Xiaoming Fu and Zuoying Tang, 17th IEEE International Conference on Network Protocols (ICNP 2009), Princeton, New Jersey, USA,
IEEE, October 2009.
Zusammenfassung lesen
To ensure state synchronization of signalling operations, many signaling protocol designs choose to establish “soft” state that expires if it is not refreshed. The approaches of refreshing state in multi-hop signaling system can be classified as either end-to-end (E2E) or hop-by-hop (HbH). Although both state refresh approaches have been widely used in practical signaling protocols, the design tradeoffs between state synchronization and signaling cost have not yet been fully investigated. In this paper, we investigate this issue from the perspectives of state refresh and state removal. We propose simple but effective Markov chain models for both approaches and obtain closed-form solutions which depict the state refresh performance in terms of state
consistency and refresh message rate, as well as the state removal performance in terms of state removal delay. Simulations verify the analytical models. It is observed that the HbH approach yields much better state synchronization at the cost of higher signaling cost than the E2E approach. While the state refresh performance can be improved by increasing the values of state refresh and timeout timers, the state removal delay increases largely for both E2E and HbH approaches. The analysis here shed lights on the design of signaling protocols and the configuration of the timers to adapt to changing network conditions.
PDF [176.2 kB]
Neighbor Selection Based on TIV Severity Sort Model in Vivaldi Network Coordinate System ,
Peng Sun, Yang Chen , Beixing Deng, Xing Li, 17th IEEE International Conference on Network Protocols (ICNP 2009) Poster Session,
Princeton, New Jersey, USA, October 2009.
Zusammenfassung lesen
Network Coordinate (NC) system is an efficient and
scalable mechanism to estimate the distance between Internet
hosts. However, the existence of Triangle Inequality Violation
(TIV) decreases the accuracy of NC system. With focus on
most widely used NC system, Vivaldi, we propose an effective
mechanism of neighbor selection based on TIV Severity Sort to
improve Vivaldi performance. By sorting existing hosts based on
corresponding edges’ TIV severity, the 90th percentile relative
error(NPRE) of Vivaldi is decreased by 13.9%. The convergence
rate is improved, and the final median prediction error is 7.9%
smaller.
ICNP_SunPeng.pdf [171.3 kB]
Traffic Localization for P2P-Applications: The ALTO Approach ,
Jan Seedorf, Sebastian Kiesel, and Martin Stiemerling , , Ninth International Conference on Peer-to-Peer Computing (IEEE P2P 2009),
IEEE, September 2009.
Zusammenfassung lesen
Today, most P2P applications do not consider locality on the underlying network topology when choosing their neighbors on the P2P routing layer. As a result, participating peers may experience long delays and peers’ ISPs suffer from a large amount of (costly) inter-ISP traffic. One potential solution to mitigate these problems is to have ISPs or third parties convey information regarding the underlying network topology to P2P-clients through a dedicated service. Following this approach, the IETF has recently formed an Application Layer Traffic Optimization (ALTO) working group for standardizing a protocol to enable P2P applications to obtain information regarding network layer topology. This paper comprises the problem space for such an ALTO approach, taking into account recent developments in the IETF ALTO Working Group. In particular, we will describe requirements for an ALTO protocol identified in the IETF, concrete protocols which have been proposed so far, and the overall challenges. In addition, we will discuss related issues such as privacy considerations, the relationship of an ALTO service with existing caching solutions, discovery mechanisms for an ALTO service, and security considerations.
P2P_2009_industry_session_ALTO_final.pdf [132.8 kB]
Understand the Unfairness of BitTorrent ,
Zengbin Zhang, Yao Li, Yang Chen , Pei Cao, Beixing Deng, Xing Li, In the Poster session of ACM SIGCOMM 2009 (SIGCOMM'09),
August 2009.
Zusammenfassung lesen
BitTorrent (BT) is the most popular P2P file-sharing application. Its tit-for-tat mechanism aims to guarantee the efficiency and fairness of sharing. However, while BT’s download efficiency has been proven, we find that the current protocol suffers seriously from unfairness, in the sense that
certain peers will always serve as Super Peers. In this paper, we report on experiments conducted to pinpoint the cause of unfairness. The results indicate that the occurrence of Super Peer has a strong correlation with the bandwidth between
the initial seed and the peer, and a weak correlation with the start time of the peer.
BT_SIGCOMM09.pdf [68.7 kB]
Interest based automated content exchange in 7DS ,
Florian Tegeler , Technical Report IFI-TB-2009-02, Institute of Computer Science, University of Goettingen,
ISSN 1611-1044, August 2009.
Zusammenfassung lesen
With the increasing storage space and performance of today's mobile devices, users often store a large variety of content like music on their devices. We argue, that leveraging this data to extract a meaningful user interest representation on the given data can help developing next generation mobile services. The mobile device can be enabled to automatically detect and predict the users
interest and automatically acquire such information. We are especially targeting at scenarios where the mobile device is not always connected to a global infrastructure such as the internet or a provided cellular net but moves in an
often communication disrupted manner. Typically such scenarios are referred to as mobile delay/disruption tolerant networks (mobile DTNs). We present a prototype that automatically analyzes a users content, derives the interest and exchanges data with other nodes having content of similar interest space. The two prototype media types we chose are music and news, while music represent time and location independent general user's interest based media. News files are an example for highly time and location critical media which is not only based on the general user's interest but has to include additional dimensions
that can be highly dynamical. We present the general architecture of our solution and highlight some technical details of our implementation proving the flexibility and extensibility of our approach.
PDF [721.2 kB]
Fast Rerouting for IP Multicast in Managed IPTV Networks ,
Ralf Lübben , Guangzhi Li, Dongmei Wang, Robert Doverspike, and Xiaoming Fu , IEEE International Workshop on Quality of Service (IWQoS 2009), Charleston, SC, USA,
July 2009.
Zusammenfassung lesen
Recent deployment of IP based multimedia distribution, especially broadcast TV distribution has increased the importance of simple and fast restoration during IP network failures for service providers. In this paper, we propose and evaluate a simple but efficient method for fast rerouting of IP multicast traffic during link failures in managed IPTV networks. More specifically, we devise an algorithm for tuning IP link weights so that the multicast routing path and the unicast routing path between any two routers are failure disjoint, allowing us to use unicast IP encapsulation for undelivered multicast packets during link failures. We demonstrate that, our method can be realized with minor modification to the current multicast routing protocol (PIM-SM). We run our prototype implementation in Emulab which shows our method yields to good performance.
PDF [166.6 kB]
Method for carrying out a QoS-oriented handoff between a first and a second IP-based, especially mobile IPV6-based, communication path, between a mobile node (MN) and a correspondent node (CN) ,
Changpeng Fan, Andreas Festag, Xiaoming Fu , Cornelia Kapper, Holger Karl, Mirko Schramm, and Günter Schäfer (inventors), granted patent, No. EP20010953886,
July 2009.
Zusammenfassung lesen
The invention relates to a method for carrying out a QoS-oriented handoff between a first and a second IP-based, especially mobile IPv6-based, communication path, between a mobile node (MN) and a correspondent node (CN), the second communication path being part of a number of communication paths which can be accessed by the mobile node, with no, one, or a plurality of intermediate instances. The inventive method comprises at least the following steps: (a) a communication path is selected from the communication paths which can be accessed by the mobile node, as a second communication path; (b) a message (BU) is generated by the mobile node, said message containing at least one IP address which is associated with the mobile node on the basis of the selected communication path, and containing minimum quality of service requirements (QoS) in terms of the selected communication path; (c) the ability to meet at least the minimum quality of service requirements is controlled and optionally ensured by the individual intermediate instances through which the message passes successively, on the selected communication path and/or through the correspondent node. The message contains the minimum quality of service requirements for a communication from the mobile node to the correspondent node and/or vice versa. A handoff is automatically carried out between the first communication path and the second selected communication path, when at least the minimum quality of service requirements are met or the message is stopped. A notice is generated in an intermediate instance and/or in the correspondent node and is sent to the mobile node if the ability to meet the minimum quality of service requirements is not ensured.
Loop-Free Forwarding Table Updates with Minimal Link Overflow ,
Lei Shi , Jing Fu, and Xiaoming Fu , Proceedings of IEEE International Conference on Communications (ICC 2009), Dresden, Germany,
June 2009.
Zusammenfassung lesen
The forwarding paths in an IP network may change due to a link failure, network equipment maintenance or reconfiguration of link weights, then the forwarding tables in the routers need to be updated. These updates may cause transient loops and transient link overflow, if they are not performed in an appropriate order. While existing work has been done to achieve loop-free updates, transient link overflow is still a problem during the update process. In this paper, we present a method that compares the initial and final forwarding paths, and obtains the updatable nodes that do not cause any transient loop or transient link overflow. However, there is not always such kind of nodes so that the forwarding tables may not converge to the final one without causing link overflow. Therefore, we propose an algorithm to update the forwarding tables that will refrain the link overflows to a minimal level. The performance study on a real topology with two setups confirms that our approach achieves smaller link overflow than using a previously proposed approach.
PDF [219.0 kB]
TORI: User Provided Future Networking Testbeds ,
Martin Stiemerling , Marcus Brunner, Sebastian Kiesel, and Xiaoming Fu , IEEE International Workshop on the Network of the Future, in conjunction with IEEE ICC 2009, Dresden, Germany,
IEEE, June 2009.
Zusammenfassung lesen
The usage of testbeds is considered a key tool for exploring the development of new protocols and network architectures in the area of network research. Testbeds, together with simulations, are the basic tool set of network researchers to drive research, but often it is impossible to get feedback from real deployments and their respective data traffic. Today’s major testbed facilities, e.g., VINI and PlanetLab, aim at emulating the behavior of large-scale networks, but they are still several orders of magnitude smaller than the deployed operational network infrastructure. We argue that it is time to extend network research beyond theoretical and testbed approaches towards a dynamic, peer-to-peer based testbed environment, similar to the approach taken by seti@home and BOINC. We aim at expanding the total number of participating nodes in an experiment and at experimenting on existing operational infrastructure with its entirely uncontrollable environment. Our vision presented in this paper, the Testbed on Real Infrastructure (TORI), includes regular end hosts (peers) in an experiment by deploying and executing the experimental software on these peers and to form an overlay network upon them. The main difference of our TORI approach compared to others is installing new technologies and testing them with the operational infrastructure.
tori-final.pdf [141.2 kB]
Interest-based Peer-to-Peer Group Management ,
Jun Lei , Xiaoming Fu , Second IEEE/ACM International Workshop on Future Multimedia Networking (FMN 2009), Coimbra, Portugal,
Springer LNCS, June 2009.
Zusammenfassung lesen
Peer-to-Peer systems become popular applications but suffer from insufficient resource availability which is caused by free-riders and inefficient lookup algorithms. To address the first cause, a number of recent works have focused on providing appropriate incentive mechanisms to encourage participants to contribute their resources to the P2P systems. To improve the lookup efficiency, locality-aware peer management has been introduced into the research community. However, existing proposals attempt to optimize the service performance during the data transmission period mostly after performing the neighboring lookup, which cannot address the fundamental concern of reducing lookup traffic. Besides, existing implementations select available contributors among random neighbors suggested by a specific server. Therefore, this paper proposes interest-based peer-to-peer management (IPM) protocol to facilitate the peering lookup. Our design philosophy differs from existing work that IPM is a client-only approach and can be represented as either an alternative or a complementary to the current proposals. With additional locality-awareness considerations, IPM can reduce the lookup overhead while optimizing the P2P traffic performance. The simulation results essentially state that IPM can largely improve the efficiency and reliability of P2P media distribution systems, for instance, reduces control overhead by 50% on average and reduces average packet loss rate up to 34.7%.
PDF [234.0 kB]
I-PMIP: An Inter-Domain Mobility Extension for Proxy Mobile IP ,
Niklas Neumann , Jun Lei , Xiaoming Fu , Gong Zhang, in the Proceedings of 5th International Wireless Communications and Mobile Computing Conference (IWCMC 2009), Leipzip, Germany,
ACM Digital Library, June 2009.
Zusammenfassung lesen
Proxy Mobile IP (PMIP) provides a solution for network-based localized mobility management which in contrast to host-based mobility solutions, like Mobile IP (MIP), does not require changes to the end-hosts and avoids tunneling overhead between the mobile node and it's network access point. Within a PMIP-enabled mobility domain, the mobile node is able to maintain the same IP address when it moves. However, if the mobile node leaves this domain the mobility support breaks. This paper proposes an extension to PMIP, called I-PMIP which allows to interconnect multiple PMIP-enabled mobility domains to provide continuous mobility support for a mobile user. I-PMIP is based on an architecture that can provide a mobile node with an anchor point that is placed very close towards the mobile. Numerical analysis show that the approach is comparable to other approaches that provide inter-domain mobility.
PDF [231.4 kB]
XOR Rescue: Exploiting Network Coding in Lossy Wireless networks ,
Fang-Chun Kuo , Kun Tan, Xiang-Yang Li, Jiansong Zhang and Xiaoming Fu , 6th IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks (SECON 2009), Rome, Italy,
June 2009.
Zusammenfassung lesen
It is well-known that wireless links are error-prone and require retransmissions for recovering frames from errors and losses. Network coding (NC) has been proposed for more efficient MAC-layer retransmissions in WLANs. However, existing schemes employed the reception report mechanism, which is both inefficient and expensive. Furthermore, they considered neither fairness nor the effects of time-varying heterogeneous wireless networks. These issues are critical for achieving full benefit of network coding. Without addressing them, these schemes may even impair system performance. In this paper, a novel MAC-layer retransmission scheme, namely XOR Rescue(XORR) is proposed. It estimates the reception status without extra overheads and devises a new coding metric, which accommodates the effects of the frames size and the channel condition. Finally, XORR employs NC-aware fair opportunistic scheduling, which is theoretically proven to be fair, i.e. not only the service time is evenly allocated, but also it always improves the expected goodput for every wireless station. It is further verified by theoretic analyses, extensive simulations and testbed experiments. Our results show that XORR outperforms the non-coding fair opportunistic scheduling and 802.11 by 25% and 40%, respectively.
PDF [307.7 kB]
Security Analysis of IKEv2 Session Resumption ,
Florian Tegeler , Technical Report No. IFI-TB-2009-01, Institute of Computer Science, University of Goettingen,
ISSN 1611-1044, June 2009.
Zusammenfassung lesen
This document describes the security analysis of a proposed IKEv2 Session Resumption method based on Sheffer, Y., Tschofenig, H., Dondeti, L. and Narayanan, V.: IPSec Gateway Failover Protocol (http://www.ietf.org/Internet-drafts/draft-sheffer-ipsecfailover-02.txt).
PDF [1112.5 kB]
Proceedings of the 1st ACM International Workshop on Hot Topics of Planet-scale Mobility Measurement (HotPlanet'09) ,
Xiaoming Fu , Pan Hui (editors), Krakow, Poland,
ACM Press, ISBN 978-1-60558-689-2, June 2009.
Phoenix: Towards an Accurate, Practical and Decentralized Network Coordinate System ,
Yang Chen , Xiao Wang, Xiaoxiao Song, Eng Keong Lua, Cong Shi, Beixing Deng, Xing Li, In Proc. of 8th International IFIP-TC6 Networking Conference (Networking 2009),
May 2009.
Zusammenfassung lesen
Network coordinate (NC) system allows efficient Internet distance prediction with scalable measurements. Most of the NC systems are based on embedding hosts into a low dimensional Euclidean space. Unfortunately, the accuracy of predicted distances is largely hurt by the persistent occurrence of Triangle Inequality Violation (TIV) in measured Internet distances. IDES is a dot product based NC system which can tolerate the constraints of TIVs. However, it cannot guarantee the predicted
distance non-negative and its prediction accuracy is close to the Euclidean distance based NC systems. In this paper, we propose Phoenix, an accurate, practical and decentralized NC system. It adopts a weighted model adjustment to achieve better prediction accuracy while it ensures the predicted distances to be positive and usable. Our extensive Internet trace based simulation shows that Phoenix can achieve higher prediction accuracy than other representative NC systems. Furthermore, Phoenix
has fast convergence and robustness over measurement anomalies.
Networking09_Phoenix.pdf [2929.9 kB]
Routing and Scheduling for WiMAX Mesh Networks ,
Jianhua He, Xiaoming Fu , Jie Xiang, Yan Zhang and Zuoyin Tang, in: Y. Zhang (ed.), WiMAX Network Planning and Optimization,
Auerbach Publications, Taylor&Francis Group, USA, ISBN 978-1-4200-6662-3, April 2009.
Zusammenfassung lesen
The book chapter presents the recent developments and a new approach for the scheduling and (both distributed and centralized) routing issues in WiMAX mesh networks.
PDF [408.7 kB]
End-to-End versus Hop-by-Hop State Refresh in Soft State Signaling Protocols ,
Jianhua He, Xiaoming Fu , Zuoyin Tang, and Hisiao-Hwa Chen, IEEE Communications Letters, 13(4): 268-270,
IEEE, April 2009.
Zusammenfassung lesen
The concept of soft state (i.e., the state that will expire unless been refreshed) has been widely used in the design of network signaling protocols. The approaches of refreshing state in multi-hop networks can be classified to end-to-end (E2E) and hop-by-hop (HbH) refreshes. In this article we propose an effective Markov chain based analytical model for both E2E and HbH refresh approaches. Simulations verify the analytical models, which can be used to study the impacts of link characteristics on the performance (e.g., state synchronization and message overhead), as a guide on configuration and optimization of soft state signaling protocols.
PDF [168.3 kB]
A Unified Security Backplane for Trust and Reputation Systems in Decentralized Networks ,
Florian Tegeler , Jun Lei , and Xiaoming Fu , IEEE INFOCOM 2009 Student Workshop,
April 2009.
Zusammenfassung lesen
Trust and Reputation (TR) systems are a recently proposed means to address free-rider issues in decentralized networks such as P2P, DTNs, and wireless mesh networks. Basically, TR systems identify malicious node behaviors by observation and direct interaction experience. However, these systems often lack a security framework to prevent a variety of attacks, such as identity spoofing or capturing and false reports on nodes behavior. We present a security backplane preventing such attacks by providing authentication, non-repudiation and other security services without predetermining the exact TR algorithm on node interaction selection and the metrics on the evaluation of nodes. Utilizing this security framework, multiple proposed algorithms such as Scrubber, Eigentrust, CONFIDENT or pricing systems can be implemented with increased and flexible security properties.
PDF [79.8 kB]
An encoding method to signal 3 states with a single PCN bit ,
Mayutan Arumaithurai , Ruediger Geib, Rene Rex , and Xiaoming Fu , IEEE INFOCOM 2009 Student Workshop,
April 2009.
Zusammenfassung lesen
Pre-Congestion Notification (PCN) is currently being developed by the IETF to provide admission control in DiffServ networks for non-elastic flows. Various marking schemes are being proposed as part of this effort. We evaluate a new marking behaviour that could be used to signal three different states by means of a single bit. This scheme is of interest to networks operating with MPLS as the Label
QoS coding space is limited to three EXP bits. Similar to the ECN standard for MPLS, this research assumes that just two codepoints will be available to indicate different congestion states. Of these two codepoints, one would be used to differentiate between PCN and non-PCN traffic and the other would be used for PCN marking. This paper outlines the approach and presents the advantages and limitations of the proposal using the evaluations performed. A comparison of the method with a two bit PCN marking approach is also studied.
pcn-markingPoster.pdf [106.3 kB]
Pharos: Accurate and Decentralised Network Coordinate System ,
Yang Chen , Yongqiang Xiong, Xiaohui Shi, Jiwen Zhu, Beixing Deng, Xing Li, IET Communications, 539-548,
April 2009.
Zusammenfassung lesen
Network coordinates (NC) system is an efficient mechanism for Internet distance prediction with scalable measurements. The intrinsical cause for the unsatisfactory accuracy of the simulation-based NC algorithms has been identified. Then Pharos, a fully decentralised and hierarchical scheme, is proposed to solve this problem. Pharos leverages multiple coordinate sets at different distance scales, with the right scale
being chosen for prediction each time. We evaluate the performance of Pharos system with the King data set and latency data from PlanetLab, and compare it with the representative NC system, Vivaldi. The experimental results show that Pharos greatly outperforms Vivaldi in Internet distance prediction without adding any significant overhead. Our extensive evaluation results also demonstrate that Pharos can significantly improve
the performance in distributed Internet applications, such as overlay multicast and server selection.
IET_Pharos.pdf [546.4 kB]
ALTO H1/H2 Protocol ,
Martin Stiemerling , Sebastian Kiesel, Internet Engineering Task Force, Internet draft (draft-stiemerling-alto-h1h2-protocol-00) , work in progress, Application Level Transport Optimization (ALTO) Working Group,
March 2009.
Zusammenfassung lesen
Many Internet applications are used to access resources, uch as pieces of information or server processes, which are available in several equivalent replicas on different hosts. This includes, but is not limited to, peer-to-peer file sharing applications. The goal of Application-Layer Traffic Optimization (ALTO) is to provide guidance to applications, which have to select one or several hosts from a set of candidates, that are able to provide a desired resource. This memo proposes one possible way of implementing the ALTO protocol, called H1H2. The H1H2 protocol is a client/server protocols between end hosts and ALTO servers that allows two different ways of exchanging data between the server and the client.
draft-stiemerling-alto-h1h2-protocol-00.txt [12.3 kB]
Overhead and Performance Study of the General Internet Signaling Transport (GIST) Protocol ,
Xiaoming Fu , Henning Schulzrinne, Hannes Tschofenig , Christian Dickmann , and Dieter Hogrefe, ACM/IEEE Transactions on Networking, 17(1): 158-171,
February 2009.
Zusammenfassung lesen
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. 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 Goettingen, and study its performance in a Linux testbed. A GIST node serving 45,000 signaling sessions is found to consume average only 1.1 ms for processing a signaling message and 2.4 KB of memory for managing 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 that it is comparable to an RSVP implementation.
PDF [210.7 kB]
Biannual Report of Computer Networks Group at the University of Göttingen (2007-08) ,
Xiaoming Fu (ed.),
February 2009.
Zusammenfassung lesen
A (bi)annual report series for the Computer Networks Group at the University of Göttingen intends to review the most relevant and important research results and other achievements and activities performed by the research group. The present report summarizes 2007-2008, the first period that the group got lounched.
PDF [137.9 kB]
A Cross-Layer Approach for Improving TCP Performance in Mobile Environments ,
Deguang Le , Xiaoming Fu , and Dieter Hogrefe, Wireless Personal Communications,
Springer Verlag, 2009.
Zusammenfassung lesen
Network-layer mobility protocols have been developed to keep continuous connectivity for mobile hosts while transparent to the higher layers. However, Due to its distinct characteristics of different from traditional TCP/IP environment, mobility poses substantial impacts on TCP performance in mobile environments.
This paper proposes a new cross-layer approach, by introducing a mobility detection element in the network layer which interacts with the transport layer to optimize TCP operations. As changes are only made to the endpoints, this approach preserves the end-to-end semantics of TCP. Different from most exiting works, which utilize either transport or network layer alone without much cross-layer cooperation, our approach allows the use of mobility information in TCP. We analytically compare this approach against existing approaches and show that our approach outperforms prior approaches in terms of effective data resumption time. Through performance simulations, our approach demonstrates that it can effectively improve TCP performance in Mobile IPv6-based mobile environments.
PDF [758.2 kB]
An Experimental Analysis of Joost Peer-to-Peer VoD Service ,
Jun Lei , Lei Shi , Xiaoming Fu , Peer-to-Peer Networking and Applications (in press),
Springer Verlag, 2009.
2008
Diameter WebAuth: An AAA-based Identity Management Framework for Web Applications ,
Niklas Neumann , and Xiaoming Fu , The 51th Annual IEEE Global Telecommunications Conference (GLOBECOM 2008), Computer and Communications Network Security Symposium, New Orleans, LA, USA,
IEEE, December 2008.
Zusammenfassung lesen
With an increasing number of personalized information and services offered on the Internet, especially the World WideWeb, effective identity management solutions are demanded by application providers. Instead of a web-based stand-alone approach, we extend existing network-based AAA mechanisms to be usable for identity management by web applications. Our proposal, Diameter WebAuth, allows to seamlessly integrate web-based services into a Diameter infrastructure for authentication, authorization, credit-control and identity management purposes. Diameter WebAuth offers comparable features to web-based identity management solutions, benefits from the maturity and wide deployment of the Diameter protocol, and takes advantage of existing AAA setups.
PDF [253.4 kB]
Performance Study of the NSIS QoS-NSLP Protocol ,
Mayutan Arumaithurai , Xiaoming Fu , Bernd Schloer , and Hannes Tschofenig , The 51th Annual IEEE Global Telecommunications Conference (GLOBECOM 2008), Next Generation Networks, Protocols, and Services Symposium, New Orleans, LA, USA,
IEEE, December 2008.
Zusammenfassung lesen
This paper presents an evaluation of the Quality of Service Signalling Layer Protocol (QoS-NSLP) of the NSIS (Next Steps In Signalling) protocol suite. The QoS-NSLP in combination with the NSIS Transport Layer Protocol (NTLP) is proposed by the Internet Engineering Task Force (IETF) as an alternative to the Resource reSerVation Protocol (RSVP). We describe our implementations of the software architecture, both on a network simulator and on a Linux implementation. Both implementations are used in a complimentary manner to illustrate the performance of the QoS-NSLP protocol. The results show the performance of QoS-NSLP with respect to resource consumption, packet processing time, session set up time, refresh interval and protocol overhead. Furthermore, we analyse the protocol performance during route change scenarios.
PDF [328.7 kB]
Evaluating P2PSIP under Attack: An Emulative Study ,
Jan Seedorf, Frank Ruwolt, Martin Stiemerling , and Saverio Niccolini, IEEE Globecom 2008, New Orleans, LA, USA,
December 2008.
Zusammenfassung lesen
Recently, establishing a VoIP call using a P2P network instead of regular SIP-servers has been proposed; this novel approach to SIP-signaling is commonly referred to as P2PSIP and technically based on a Distributed Hash Table (DHT). P2P networks are advantageous with respect to reliability and scalability. However, securing DHTs against adversary nodes which intentionally interrupt functionality of the network remains a major research problem. In particular, even if a trusted enrollment server is used for secure identifier assignment of participating nodes, attacks on overlay routing by malicious nodes that have successfully joined the network can still severely degrade the lookup service of the DHT.
To gain insight into the ability of callers to reach callees during such attacks on DHT-routing, we present the first P2PSIP implementation that enables to emulate adversary nodes as well as the injection of a large amount of lookup requests (i.e., SIP-Invite requests) in an automated way. Further, we implemented several secure DHT routing algorithms and investigated their effect on the success rate of lookups and the maximum call-setup time in an infiltrated P2PSIP network. In general, our system provides the ability to analyze attacker behavior as well as future novel security techniques in an actual P2PSIP environment with comparably low effort.
PDF [529.3 kB]
Forschungsrichtungen der Internettechnologie - Kein Tempolimit für die Datenautobahn ,
Xiaoming Fu , Dieter Hogrefe, and Henning Schulzrinne, Georg Augusta, special issue on Mathematics and Computer Science Year 2008, Vol. 6, 112-118, pages ,
ISSN 0016-8157, December 2008.
Zusammenfassung lesen
Während eine Vielzahl von Standardanwendungen der Internettechnologie fest in unser Arbeits- und Alltagsleben integriert ist, arbeiten Forscher intensiv an neuen Anwendungen, verbesserten Sicherheitsstandards und benutzerfreundlichen Diensten. Am Göttinger Institut für Informatik kamen im Juni diesen Jahres mit Unterstützung des Deutschen Akademischen Austauschdienstes (DAAD) etwa 20 Wissenschaftler der Columbia University, New York, und der Georg-August-Universität zusammen, um sich über den Stand der Forschung im Bereich Internettechnologie auszutauschen. Auf dem „1st Columbia-Göttingen Workshop on Internet Research“ wurden auch für die Göttinger Forschung wichtige Themen der Internettechnologie präsentiert, die von drahtlosen Technologien und Mobilkommunikation über Verkehrsanalyse und Stauvermeidungstechnologien, über Overlay und Peer-To-Peer-Netze bis hin zu Voice over IP und ortsbasierten Anwendungen reichten. Der Beitrag gibt einen Einblick in den Stand wichtiger Bereiche der Technik und stimuliert die Diskussion über Visionen des zukünftigen Internets.
PDF [301.9 kB]
GIST State Machine ,
Tseno Tsenov, Hannes Tschofenig , Xiaoming Fu , Cedric Aoun, and Elwyn Davies, Internet Engineering Task Force, Internet draft (draft-ietf-nsis-ntlp-statemachine-05), work in progress, Next Steps in Signaling (NSIS) Working Group,
November 2008.
Zusammenfassung lesen
This document describes the state machines for the General Internet Signaling Transport (GIST). The states of GIST nodes for a given flow and their transitions are presented in order to illustrate how GIST may be implemented.
PDF [633.8 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,
October 2008.
Zusammenfassung lesen
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.
TXT [22.0 kB]
Decoupling Congestion Control Using Traffic Aggregates and Middleboxes ,
Niklas Neumann , Ralf Lübben , Mayutan Arumaithurai , and Xiaoming Fu , IEEE International Conference on Network Protocols (ICNP 2008), poster session, Orlando, FL, USA,
October 2008.
Zusammenfassung lesen
A rise in numbers of large bandwith-delay product links and an increasing heterogeneity of IP networks bring new challenges for the existing congestion control mechanisms. Congestion control mechanisms are traditionally end-to-end oriented. This makes them slow to react on high delay links and inaccurate if the flow traverses heterogeneous network segments that have different jitter, or packet loss rates. Furthermore, the slow start which TCP uses as part of its congestion control is slow to react on high bandwith-delay product links and makes it hard for short-lived flows to develop fully.
We propose to decouple the end-to-end congestion control mechanisms by introducing middleboxes to create dedicated congestion control segments within the network. Within those segments congestion control mechanisms can be deployed that are specifically adapted to the particular properties of this segment.
PDF [198.7 kB]
Firewall Traversal in Mobile IPv6 Networks ,
Niklas Steinleitner , PhD thesis, Faculty of Mathematics and Computer Science, University of Goettingen, Germany,
October 2008.
Implementation and Analysis of HTTP Enabled Location Delivery and Location-to-Service Translation Clients for IP-based Emergency Calls ,
Benedikt Schäffler , Bachelor's thesis, No. ZFI-BSc-2008-04, Center of Computational Sciences, University of Goettingen, Germany,
ISSN 1612-6793, October 2008.
Zusammenfassung lesen
Nowadays, location-based services such as location specific advertisements and emergency services are becoming very popular. This thesis looks at one such service namely the Emergency Context Resolution with Internet Technologies (ECRIT) framework. This is the first attempt to realize emergency calls in an IP based infrastructure. This thesis studies the HTTP Enabled Location Delivery protocol (HELD) and the Location-to-Service Translation protocol (LoST), the two basic elements of the ECRIT framework. In this respect a HELD client and LoST client are implemented. The HELD client requests the location of a device whereas the LoST client uses this location to request a local emergency service. Furthermore, three different scenarios of the ECRIT framework are developed in which the HELD client and the LoST client collaborate to do IP based emergency calls. These three scenarios are analyzed with regards to pros and cons with the objective of determining one final solution. Furthermore, a performance analysis of both clients was executed to determine how the device, the clients are running on, affects their processing time.
thesis.pdf [934.0 kB]
Implications and Control of Middleboxes in the Internet ,
Xiaoming Fu , Martin Stiemerling , and Henning Schulzrinne, IEEE Network, Special Issue on Implications and Control of Middleboxes in the Internet,
September 2008.
Zusammenfassung lesen
Middleboxes in the Internet have been explored, sometimes quite controversially, in operations, standardization, and the research community for more than 10 years. The main concern, on one hand, has been their contradicting nature to the Internet's end-to-end principle. On the other hand, middleboxes were introduced in the Internet for various reasons. In this special issue we are pleased to introduce a series of state-of-the-art articles on this specific area. These articles cover the subject from a variety of perspectives, offering the readers an understanding of the issues and implications of various middleboxes in the Internet, including their control mechanisms.
PDF [140.6 kB]
Evaluating the benefits of introducing PMIPv6 for localized mobility management ,
Jun Lei , and Xiaoming Fu , in the Proceedings of International Wireless Communications and Mobile Computing Conference 2008 (IWCMC 2008), Crete, Greece, Pages 74-80,
IEEE, August 2008.
Zusammenfassung lesen
Abstract—Since recent years, it has been recognized that using global mobility protocol for managing localized mobility causes a number of problems, such as a long registration delay. To overcome these problems, Proxy Mobile IPv6 is proposed, which can avoid tunneling overhead over the air and support for hosts without an involvement in the mobility management. In this paper, we first discuss the recent localized mobility proposals and explore three major benefits that PMIPv6 can bring. In particular, we evaluate two aspects of the handover performance through a simple mathematical model for Fast Handovers for MIPv6, Hierarchical MIPv6, Fast handovers for HMIPv6 and PMIPv6. These analytical studies show that PMIPv6 may cause high handover latency if the local mobility anchor is located far from the current mobility access gateway. Therefore, some enhancements for PMIPv6 are suggested to further reduce the handover latency. The analysis ascertains that F-PMIPv6 is a promising mobility scheme to efficiently manage the localized mobility.
PDF [206.1 kB]
D-MORE: Dynamic Mesh-based Overlay Peer-to-Peer Infrastructure ,
Jun Lei , Xiaoming Fu , and Dieter Hogrefe, Technical Report No. IFI-TB-2008-02, Institute of Computer Science, University of Goettingen, Goettingen, Germany,
ISSN 1611-1044, August 2008.
Zusammenfassung lesen
Traditionally, Internet Service Providers (ISPs) have
to interconnect with content providers to provide network services
to customers. Current business model that connectivity
and bandwidth become commodities has motivated ISPs to
distribute content and other application-specific services to their
customers using their own infrastructure. It is desirable for
ISPs to economize existing infrastructure to support a variety
of applications and services.
We propose a dynamic mesh-based overlay peer-to-peer infrastructure
and illustrate its two examples usage cases among other
potentials. We describe several key techniques, namely capacity
classification, locality-awareness and incentive mechanisms for
construction of the tiered infrastructure. Through extensive
simulations, we show D-MORE scales well with an increasing
number of hosts, in terms of control overhead, link stress and
data path length, for supporting media distribution services.
We propose further improvements to enhance the D-MORE
performance, which brings up to 35% network resource savings
and up to 200% control overhead reduction in our simulations.
PDF [539.6 kB]
Network coding-aware fair opportunisic scheduling in wireless networks ,
Fang-Chun Kuo , Kun Tan, Xiang-Yang Li, Jiansong Zhang, and Xiaoming Fu , Technical Report No. IFI-TB-2008-03, Institute of Computer Science, University of Goettingen, Goettingen, Germany,
ISSN 1611-1044, August 2008.
Zusammenfassung lesen
Users increasingly depend on WLAN for business and entertainment. It is well-recognized that wireless links are prone to errors. Previous work, ER, proposed to use network coding (NC) for providing more efficient MAC-layer
retransmission scheme in WLAN. However, it uses inefficient and costly reception report scheme and does not consider the effect of heterogeneous and time-varying wireless conditions and fairness. These issues are critical for getting full benefits of network coding. We show that, without addressing them, NC may even cause negative effect on the system. In this paper, we present a novel MAC-layer retransmission scheme, namely XORR, which uses reception estimation without extra overhead and adopts NC-aware opportunistic scheduling with maintaining temporal fairness in WLAN. We prove our NC-aware scheduling algorithm is fair and it will always improve the expected goodput for each wireless clients. We further verify XORR with extensive simulation as well as experiment studies and find that our scheme outperforms traditional opportunistic scheduling (without NC) and 802.11 about 25% and 40%, respectively.
PDF [476.7 kB]
Media Distribution using Overlay Multicast and Peer-to-Peer Technologies ,
Jun Lei , PhD thesis, Faculty of Mathematics, University of Goettingen, Germany,
July 2008.
Evaluation and Improvement of Security in ZigBee Networks ,
Sufian Hameed ,
Institute of Informatik, RWTH Aachen, June 2008.
Zusammenfassung lesen
ZigBee, an increasingly adopted WSN standard, is the upcoming standard for simple, short-range, low-footprint and low-power wireless connectivity. It is a specification of high level communication protocol suits on top of IEEE 802.15.4 developed by ZigBee Alliance. Typicalapplication areas of ZigBee include industrial control, health care, energy metering, commercial building automation and home automation.
With the expected growth in ZigBee implementations and the evolution of broader sensor network applications, the topic of security has become highly pronounced. Key distribution and establishment serves as an important pillar for all the basic security services such as, e.g. confidentiality, authentication or access control as it provides the secrets necessary to enable the basic security services. Many security architectures, including ZigBee, are based on centralized approach using a central authority for key establishments (KE). Other approaches propose the use of distributed KE protocols. Both solutions present different issues like scalability, computational requirements, multi-hop scenarios where the central authority being distant or single point of failure. Further application of security burdens the data flow with increased packet size and computations, resulting in delays and communication bottlenecks.
Within this thesis we evaluated the performance of ZigBee medical network for the centralized key establishment (KE) and different security levels and modes as specified by ZigBee. For evaluation via simulations, we have implemented all proposed mechanisms in Network Simulator (NS2) allowing us to simulate specific scenarios with real settings.
With centralized architecture Trust Center (TC) is responsible for the key distribution and establishment. This results in long delays for key establishment in large multi hops networks. For improvement we introduced, analyzed and simulated the ZigBee operation when key
establishment is carried out in a distributed way. The results show that the system performs faster and in a more reliable way. Finally, we optimized different security parameters used to provide basic security services such confidentiality or authentication to reduce the security overhead. In special, the refreshness counters used for replay protection are optimized using last bit optimization technique [MiniSec], resulting in reduction of transmission overheads and energy consumptions.
TCP Performance Enhancement in Wireless Environments: Prototyping in Linux ,
Swen Weiland , Bachelor's thesis, No. GAUG-ZFI-BSC-2008-05, Center of Computational Science, University of Goettingen, Goettingen, Germany,
ISSN 1612-6793, May 2008.
Zusammenfassung lesen
In recent years, wireless communication gets more and more popular. Future wireless standards will reach throughputs much higher than 100 Mbit/sec on link layer. However, wireless channels, as compared to wired lines, exhibit different characteristics due to fading, interference, and so on. For transport control protocol (TCP), the misinterpretation of packet loss due to wireless channel characteristic as network congestion results in suboptimal performance. There are many different approaches to enhance TCP over wireless networks, especially for slow and lossy links such as satellite connections. This thesis evaluates “TCP Snoop” as one of these approaches for high transfer rates. Finding, using and implementing effective capturing, buffering and tracking of TCP communication were the objectives to solve. A general and transparent TCP proxy with “TCP Snoop” behavior was implemented during the work for this thesis. The TCP proxy runs on an intermediate Linux host which connects wired and wireless networks as a prototype user space application with a modular design.
Different traffic capture methods are compared in portability and performance. A full TCP connection tracking is described and implemented. Design patterns and methods that proofed their benefit in practice were applied and sometimes partially modified to fit into the needs of the transparent TCP proxy. The modular design makes exchanging a low level module such as the data traffic capture module possible. Porting the implementation to another operating system, another platform like embedded systems which are used as wireless LAN routers or changing the TCP enhancement method are also eased by the modular design.
The results show that a transparent TCP proxy or other traffic modifying implementation should not reside in the user space for performance reasons. A kernel space implementation or even better a dedicated hardware like a network processor platform should be used for such implementations.
PDF [504.7 kB]
Performance Evaluation of TCP Variants over UMTS Networks ,
Nikunj Modi , Master's thesis, No. GAUG-ZFI-MSC-2008-06, Zentrum fuer Informatik, Universitaet Goettingen,
ISSN 1612-6793, May 2008.
Zusammenfassung lesen
With the evolution of 3G technologies like Universal Mobile Telecommunication System (UMTS), the usage of TCP has become more popular for a reliable end-to-end (e2e) data delivery. However, as TCP was initially designed for wired networks and therefore it suffers performance degradation due to the radio signal getting affected by fading, shadowing and interference. There are many strategies proposed by the research community on how to improve the perfor-mance of TCP over wireless links such as introducing link-layer retrans-mission, explicitly notifying the sender of
network conditions or using new variants of TCP.
As UMTS network is growing at very fast pace, optimization of various internal component of its wireless network is very important. One of the optimization is the introduction of High Speed Downlink Packet Access (HSDPA). This architecture not only allows higher data rates but also more reliable data transfer by the introduction of Hybrid ARQ (HARQ). With this enhancement in UMTS network, it becomes very vital to see the performance of TCP in such a network. Therefore in this thesis we try to evaluate two aspect of UMTS network: first, the impact of HSDPA parameters like scheduling algorithm and RLC/MAC-hs buffer size on overall performance of the TCP and second, to study the behavior of two categories of TCP: loss based and delay based. Our simulation shows that delay based TCP tends to perform better than loss based TCP in our selected scenarios. The simulations are performed in network simulator NS-2 using an e2e network model for enhanced UMTS (EURANE).
PDF [763.9 kB]
Intersystem Soft Handover for Converged DVB-H and UMTS Networks ,
Xiaodong Yang , and Thomas J. Owens, IEEE Transactions on Vehicular Technology, 57(3): 1887-1898,
May 2008.
Zusammenfassung lesen
Digital video broadcasting for handhelds (DVB-H) is the standard for broadcasting Internet Protocol (IP) data services to mobile portable devices. To provide interactive services for DVB-H, the Universal Mobile Telecommunications System (UMTS) can be used as a terrestrial interaction channel for the unidirectional DVB-H network. The converged DVB-H and UMTS network can be used to address the congestion problems due to the limited multimedia channel accesses of the UMTS network. In the converged network, intersystem soft handover between DVB-H and UMTS is needed for an optimum radio resource allocation, which reduces network operation cost while providing the required quality of service. This paper deals with the intersystem soft handover between DVB-H and UMTS in such a converged network. The converged network structure is presented. A novel soft handover scheme is proposed and evaluated. After considering the network operation cost, the performance tradeoff between the network quality of service and the network operation cost for the intersystem soft handover in the converged network is modeled using a stochastic tree and analyzed using a numerical simulation. The results show that the proposed algorithm is feasible and has the potential to be used for implementation in the real environment.
PDF [884.3 kB]
Applicability Statement of NSIS Protocols in Mobile Environments ,
Takako Sanda, Xiaoming Fu , Seong-Ho Jeong, Jukka Manner, and Hannes Tschofenig , Internet Engineering Task Force, Internet draft (draft-ietf-nsis-applicability-mobility-signaling-10), work in progress, Next Steps in Signaling (NSIS) Working Group,
April 2008.
Zusammenfassung lesen
Mobility of an IP-based node affects routing paths, and as a result, can have a significant effect on the protocol operation and state management. This draft discusses the effects mobility can cause to the NSIS protocol suite, and how the protocols operate in different scenarios, with mobility management protocols.
TXT [85.8 kB]
Handover in DVB-H: Investigations and Analysis ,
Xiaodong Yang , 168 pages,
Springer Verlag, ISBN 978-3-540-78629-0, April 2008.
Zusammenfassung lesen
This book gives a detail description of the handover issues in DVB-H networks, in converged DVB-H/UMTS networks and in hybrid DVB-H/DMB-T networks. Besides, the DVB-H signalling information including ESG is discussed. The current status and the future research directions of DVB-H and DVB-H handover are presented so that the readers can also get an overview of the research methods being used.
Although this book is research focused, it also gives a detail introduction to the basic concepts such as handover, time slicing, ESG, etc.. This book is written in a way that even people without prior knowledge of DVB-H can easily understand. At the end of each chapter there are some questions and there are solutions to those questions at the end of the book.
This book can be used by researchers, engineers, academics, regulatory bodies and business managers as a reference book, or by university students as a text book or a reference book.
Forward [264.6 kB]
Implementation and Evaluation of the Peer-to-Peer-Protocol (P2PP) for P2PSIP ,
Michael Cohrs , Master's thesis, No. ZFI-BM-2008-04, Zentrum fuer Informatik, Universitaet Goettingen,
ISSN 1612-6793, March 2008.
Zusammenfassung lesen
The peer-to-peer networking paradigm, as opposed to client-server architectures, is attractive for many fields of applications. Recently, various developments led to its adoption for real-time multimedia applications like, e.g., Internet telephony. SIP, a well-established Internet standard in this field that is usually relying on central servers, is to be reformed with peer-to-peer techniques, leading to the first Internet standard carrying P2P in its name.
The goal of this thesis is to introduce P2PSIP and conduct a prototype implementation of a proposed P2PSIP protocol that is used for the maintenance and data communication between peers in a P2PSIP overlay network. The result has been complemented with basic SIP functionality and analyzed regarding its functionality, performance and real-world applicability.
PDF [1284.0 kB]
NAT/Firewall NSIS Signaling Layer Protocol (NSLP) ,
Martin Stiemerling , Hannes Tschofenig , Cedric Aoun, and Elwyn Davies, Internet Engineering Task Force, Internet draft (draft-ietf-nsis-nslp-natfw-18), work in progress, Next Steps in Signaling (NSIS) Working Group,
February 2008.
Zusammenfassung lesen
This memo defines the NSIS Signaling Layer Protocol (NSLP) for Network Address Translators (NATs) and firewalls. This NSLP allows hosts to signal on the data path for NATs and firewalls to be configured according to the needs of the application data flows. It enables hosts behind NATs to obtain a public reachable address and hosts behind firewalls to receive data traffic. The overall architecture is given by the framework and requirements defined by the Next Steps in Signaling (NSIS) working group. The network scenarios, the protocol itself, and examples for path-coupled signaling are given in this memo.
TXT [195.5 kB]
Spam Score for SIP ,
D. Wing, S. Niccolini, Martin Stiemerling , and Hannes Tschofenig , Internet draft (work in progress),
IETF, February 2008.
Zusammenfassung lesen
This document defines a mechanism for SIP proxies to communicate a spam score to downstream SIP proxies and SIP user agents so they can provide alternate call routing or call handling.
TXT [14.5 kB]
A Network Virtualisation Concept Based on Ambient Networks SATO System ,
Martin Stiemerling , Xiaoming Fu , and Marcus Brunner, 1. GI/ITG Fachgespraech Virtualisierung, Paderborn, Germany, pages 33 - 36,
February 2008.
Zusammenfassung lesen
Network virtualization can be one way of fixing the shortcomings of todays Internet but also open the venue for new, unforeseen applications. In this extended abstract, we present a novel approach for network virtualisation based on the Service-Aware Transport Overlay (SATO) concept of Ambient Networks. SATOs introduce on-demand overlay creation and new interfaces to ease applications to use overlays.
PDF [295.8 kB]
Reports of Advanced Topics in Computer Networking and Mobile Communications (Summer 2004 - Winter 2006/2007) ,
Xiaoming Fu , and Dieter Hogrefe (editors), Technical Report No. IFI-TB-2008-01, Institute of Computer Science, University of Goettingen, Goettingen, Germany,
ISSN 1611-1044, February 2008.
Zusammenfassung lesen
This technical report includes the final reports written by students for seminars from summer semester 2004 to winter semester 2006/07 on advanced topics in computer networking/Internet research and mobile communications, including mobile, ad hoc, sensor networks and location-based systems; wireless networks, security and performance optimization issues; mobile applications and mobile devices; overlay, peer-to-peer and application layer multicast, as well as delay tolerant networks.
PDF [8327.7 kB]
Security Analysis, Prototype Implementation and Performance Evaluation of a New IPSec Session Resumption Method ,
Florian Tegeler , Zentrum fuer Informatik, Universitaet Goettingen, Master's Thesis, No. ZFI-BM-2008-01,
ISSN 1612-6793, January 2008.
Zusammenfassung lesen
In the current communication infrastructure a variety of services are already based on the Internet Protocol (IP) and effort is taken to put the mobile communication as well into the IP framework. Many of these services like voice over IP or online banking require an increased level of security and privacy, and therefore demanding a wide application of security suits as IPSec. These connections are typically secured by keys derived from a key negotiation process run with the IKEv2 key negotiation protocol. This process is computationally heavy; ideally it should be performed as rarely as possible. The computational complexity could grow to a severe problem in mobile environments where a base station is handling hundreds or thousands of mobile nodes and the gateway fails for any reason. If the gateway fails and recovers later, all IPSec capable devices will try to resume their session immediately by renegotiating keys and potentially overload the gateways resources by doing that in parallel. Furthermore the total number of clients a base station can handle is reduced when sessions to end host fail temporarily due to e.g. communication distortions etc. Every time re-keying is necessary.
In this thesis a server side stateless IPSec session resumption approach developed by Sheffer et al is presented and analysed. The sessions state including the master secret as the source for further keying material is stored in an encrypted ticket which can later be used to quickly resume the session. A formal security analysis based on CSP algebra interpreted with the CasperFDR toolkit was performed and it could be shown that no new security threats are introduced by altering the IKEv2 communication sequence and storing the state inside a ticket. Furthermore, a prototype of the ticket based session resumption was implemented into an existing open source Linux IKEv2 daemon and the performance evaluation showed a significant reduction in the session resumption time. Overall, this thesis illustrates the new ticket based session resumption approach, verifies it via a formal security toolkit and proves the significant reduction of the time required to resume a session in a prototype implementation.
PDF [2727.2 kB]
Probe-aided MulTCP: An Aggregate Congestion Control Mechanism ,
Fang-Chun Kuo , and Xiaoming Fu , ACM SIGCOMM Computer Communication Review, Vol. 38, No. 1, Pages 19-28,
ACM, ISSN 0146-4833, 2008.
Zusammenfassung lesen
An aggregate congestion control mechanism, namely Probe-Aided MulTCP (PA-MulTCP), is proposed in this paper. It is based on MulTCP, a proposal for enabling an aggregate to emulate the behavior of multiple concurrent TCP connections. The objective of PA-MulTCP is to ensure the fair sharing of the bottleneck bandwidth between the aggregate and other TCP or TCP-friendly flows while keeping lightweightness and responsiveness. Unlike MulTCP, there are two congestion window loops in PA-MulTCP, namely the probe window loop and the adjusting window loop. The probe window loop constantly probes the congestion situation and the adjusting window loop dynamically adjusts the congestion window size for the arriving and leaving flows within the aggregate. Our simulations demonstrate that PA-MulTCP is more stable and fairer than MulTCP over a wide range of the weight N in steady conditions as well as in varying congestion conditions. PA-MulTCP is responsive to flow-arriving/leaving and thus reduces the latency of short-lived transfers. Furthermore, PA-MulTCP is lightweight, since it enjoys above advantages at the cost of only an extra probe window loop, which has a marginal influence on the implementation complexity. Finally, the design of PA-MulTCP decouples the congestion management from the other functionalities in the aggregate flow management. As a result, PA-MulTCP could be potentially applied to a wider range of scenarios, e.g. wireless TCP proxies, edge-to-edge overlays, QoS provisioning and mass data transport.
PDF [758.8 kB]
2007
A Peer-to-Peer SIP System based on Service-Aware Transport Overlays ,
Martin Stiemerling , and Marcus Brunner, Praxis der Informationsverarbeitung und Kommunikation (PIK), Special Issue on Voice over IP, Volume 30, No. 4,
ISBN 978-3-598-01376-8, December 2007.
Zusammenfassung lesen
The Session Initiation Protocol (SIP) traditionally establishes and manages its sessions with centralized servers, which have been challenged by issues with TCP/IP networks right from its beginning, for instance, issues with NAT traversal or network congestions. On the other hand, there are peer-to-peer and overlay techniques that potentially can make SIP working better under various network conditions. Overlay networks can provide a good abstraction from the real network, thus hiding the presence of NATs. Some proposals on peer-to-peer SIP have been recently presented. While these proposals attempted to solve a subset of challenges faced by traditional SIP, such as removing the centralized SIP entities, there is to the best of our knowledge no single solution offering a comprehensive view of the peer-to-peer SIP architecture and operation. This paper presents a novel approach for a peer-to-peer SIP system, using overlay techniques for signalling and media transport in the Internet. This system is based on the Ambient Networks Service-Aware Transport Overlay (SATO) system. The proposed system replaces the traditional SIP proxy/registrar function with a distributed lookup mechanism, adding overlay functionality to the SIP signalling and to the RTP traffic. Moreover, different from previous proposals, our approach deliberately places media/packet relays into the SIP/RTP paths, which allows an efficient session management and media communication.
p2p-sip-system.pdf [456.5 kB]
Optimized FMIPv6 Using IEEE802.21 MIH Services in Vehicular Networks ,
Qazi Mussabbir, Wenbing Yao, Zeyun Niu, and Xiaoming Fu , IEEE Transactions on Vehicular Technology, Special Issue on Vehicular Communications Networks, Volume 56, Issue 6, Pages 3397 - 3407,
IEEE, ISSN 0018-9545, November 2007.
Zusammenfassung lesen
In this paper, we optimize the handover procedure in Fast Handover for Mobile IPv6 (FMIPv6) protocol by using IEEE 802.21 Media Independent Handover (MIH) services. FMIPv6 is used to enhance the performance of handovers in Mobile IPv6 (MIPv6) and its basic extension for Network Mobility (NEMO), the fundamental mobility management protocols used in vehicular networks. With the aid of the lower three layers information of the mobile node/router (MN/MR) and the neighboring access networks, we tackle the radio access discovery and candidate Access Router (AR) discovery issues of FMIPv6. We introduce an Information Element Container to store static and dynamic Layer 2 (L2) and Layer 3 (L3) information of neighboring access networks, and propose to use a special cache maintained by the MN/MR to reduce the anticipation time in FMIPv6, thus increasing the probability of the predictive mode of the FMIPv6 operation. Furthermore, we propose a cross-layer mechanism for making intelligent handover decisions in FMIPv6. Lower layer information of the available links obtained by MIH services as well as the higher layer information such as quality of service parameter requirements of the applications are used by a Policy Engine (PE) to make intelligent handover decision. We will show through analysis and simulations of the signaling procedure that the overall expected handover (both L2 and L3) latency in FMIPv6 can be significantly reduced in the proposed mechanism.
PDF [214.6 kB]
Peer-to-Peer SIP Implementation Report ,
Martin Stiemerling , and Marcus Brunner, Internet Engineering Task Force, Internet draft (draft-stiemerling-p2psip-impl-02), work in progress, Peer-to-Peer SIP (P2PSIP) Working Group,
November 2007.
Zusammenfassung lesen
This memo is an implementation report about the peer-to-peer SIP system developed in the European IST Ambient Networks research project. This system replaces the traditional SIP proxy-registrar function with a distributed lookup mechanism, adds overlay functionality to the SIP signalling and to RTP traffic, takes care about media/packet relay lookup and insertion into the SIP/RTP paths, plus automatic adaptation of the voice transmission according to changing network conditions. Standard, unmodified SIP user agents are used for communication. The presented system is work in progress and this memo is an attempt to gather IETF community feedback about the described approach.
TXT [24.3 kB]
Performance Evaluation of a Novel Overlay Multicast Protocol ,
David Weiss , Bachelor's thesis, No. ZFI-BM-2007-11, Zentrum fuer Informatik, Universitaet Goettingen,
ISSN 1612-6793, November 2007.
Zusammenfassung lesen
The demand for high-bandwidth media streaming over the Internet is growing. For large groups of receivers, media streaming places a heavy burden on the network. IP Multicast can alleviate this problem, but it is not widely deployed. In recent years, application layer multicast and overlay multicast have been proposed as alternatives. However, there are still concerns about the efficiency, scalability and deployment of these architectures.
In this thesis, a novel application layer multicast approach, called the Dynamic Mesh-based Overlay Multicast Protocol (DMMP), is evaluated. DMMP establishes an overlay network core consisting of super nodes, which are end-hosts with particularly high capacities. Each super node manages a cluster of non-super nodes. We use network simulations to analyze the performance of DMMP. For that purpose, we have implemented a DMMP module in OverSim. OverSim is an overlay network simulation framework based on OMNeT++.
We compare DMMP with NICE, a well-known application layer multicast protocol, that is claimed to achieve low link stress and low control overhead. We experiment with groups of up to 2048 members. Our results indicate that DMMP can achieve comparable service quality with less control overhead, and that DMMP has the potential to scale to a high number of receivers.
PDF [967.3 kB]
Diameter WebAuth: An AAA-based Identity Management Framework for Web Applications ,
Niklas Neumann , Master's Thesis, No. ZFI-BM-2007-39, Zentrum fuer Informatik, Universitaet Goettingen,
ISSN 1612-6793, November 2007.
Zusammenfassung lesen
Every day countless users are accessing various personal and personalized information on the Internet, especially the World Wide Web. In order to provide each user proper access, web applications need to be able to establish the user's identity. Identity management is a concept to unify and facilitate such user identification.
The objective of this thesis is to introduce and explore identity management in web applications. First, existing identity management approaches are analyzed and evaluated. Based on the results of this evaluation, a new AAA-based identity management framework, the so-called Diameter WebAuth, is proposed. The proposal is based on the Diameter protocol and intended for an easy deployment in web applications. By using Diameter as basis, the proposal takes advantage of existing Diameter functions and specifications and can be seamlessly integrated into existing Diameter setups. Diameter WebAuth provides features comparable to web-based identity management solutions such as OpenID, the Liberty Alliance project and Microsoft CardSpace.
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A New Decentralized Mobility Management Service Architecture for IPv6-based Networks ,
Deguang Le , Jun Lei , and Xiaoming Fu , in Proceedings of the 3rd ACM International Workshop on Wireless Multimedia Networking and Performance Modeling (WMuNeP'07), in conjunction with the 10th ACM/IEEE International Symposium on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM'07), Chania, Crete Island, Greece,
ACM Press, New York, NY, USA, October 2007.
Zusammenfassung lesen
In Mobile IPv6, the home network - through a designated home agent - is responsible for distributing all traffic from/to the mobile node in the default bidirectional tunneling mode, when the mobile node is connected to a foreign network. This approach not only lacks sufficient scalability and efficiency of delivery, but also poses a heavy burden on the home network and the global Internet. In this paper we propose a new decentralized mobility management service (DMMS) architecture to address this issue. The idea is to employ a local mobility agent in each access network, which handles node mobility based on local movement information, so that the ongoing communication can be maintained efficiently and scalable without relying on centralized traffic distributing entities.
PDF [297.9 kB]
An NSIS-based Approach for Firewall Traversal in Mobile IPv6 Networks ,
Niklas Steinleitner , Xiaoming Fu , Dieter Hogrefe, Thomas Schreck, and Hannes Tschofenig , Third Annual International Wireless Internet Conference (WICON 2007), Austin, Texas, USA,
ACM Press, October 2007.
Zusammenfassung lesen
Firewalls have been successfully deployed in todays network infrastructure in various environments and will also be used in IPv6 networks. However, most of the current firewalls do not support Mobile IPv6, the best known standardized solution for mobility support in IPv6. As a result, Mobile IPv6 traffic will be most likely dropped when used without an appropriate firewall traversal solution.
This paper describes the problems and impacts of having firewalls in Mobile IPv6 environments and presents a firewall traversal solution based on the IETFs Next Steps In Signaling framework to address these issues. Compared with other candidates such as STUN, TURN, ICE, ALG, MIDCOM
and COPS, this approach does not rely on specific firewall placements and can be applied in various operational modes without additional introducing entities. In this paper we also explore security aspects since they are typically difficult to handle.
PDF [372.2 kB]
An Experimental Analysis of Joost Peer-to-Peer VoD Service ,
Jun Lei , Lei Shi , and Xiaoming Fu , Technical Report No. IFI-TB-2007-03, Institute of Computer Science, University of Goettingen, Goettingen, Germany,
ISSN 1611-1044, October 2007.
Zusammenfassung lesen
Most of the current Video-on-Demand (VoD) systems rely on content distribution networks or some local streaming proxies. While these traditional systems offer a means for media delivery and streaming, they also pose a significant performance challenge in terms of scalability and service delay as the number of clients increases. To solve this issue, peer-to-peer (P2P) technologies have been applied to support the VoD systems. Joost is one of such systems for distributing TV shows or other forms of video over the Internet. However, like Skype in its early stage, the mechanisms behind Joost are still unrevealed.
The main purpose of this paper is therefore to study the underlying Joost architecture and its key components, and analyze its media streaming behaviors and peer management mechanisms through close investigations on Joost network traffic. With three envisioned typical scenarios we have further studied the Joost performance in terms of locality awareness, bandwidth capacity and VoD functionalities. Based on extensive experiments, we infer that Joost is a server-assisted peer-to-peer VoD system. It mainly relies on a set of delicate infrastructure nodes (e.g. content servers) for video distribution. To our best knowledge, this paper is the first analytical and performance study on commercial P2P VoD services.
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Implementation and Performance Evaluation of the IETF QoS NSLP Protocol ,
Bernd Schloer , Master's thesis, No. GAUG-ZFI-BM-2007-37, Center for Informatics, University of Goettingen, Germany,
ISSN 1612-6793, October 2007.
Zusammenfassung lesen
The main focus of this thesis is an open source implementation of the NSIS QoS NSLP with the support of signalling IntServ Controlled Load Service and its evaluation. The implementation was done in a research project at the University of Goettingen. Several software design features were introduced during the implementation work which yields in a stable and timely responsive application. The design features include a state machine, a traffic control interface and a timer library which together cover the whole functionality of the implementation.
PDF [1679.2 kB]
RTP over Datagram TLS ,
John-Patrick Wowra , Master's thesis, No. GAUG-ZFI-BM-2007-28, Center for Informatics, University of Goettingen,
ISSN 1612-6793, September 2007.
Zusammenfassung lesen
The popularity of Internet Telephony has been rising continuously in recent years. With a rising number of users inevitably the number of malicious users rises as well. Hence security is a major concern for Internet Telephony.
Commonly RTP is used with Internet Telephony for transmission and reception of audio and video data. Traditionally, RTP runs over UDP, and RTP traffic is in most cases transmitted without any protection.
Datagram TLS is a modified version of TLS that functions properly over datagram transport. This thesis studies an RTP extension based on DTLS, and includes conduction of a prototype implementation and further analysis of the design towards securing RTP and thus Internet Telephony.
PDF [1248.2 kB]
An overview of digital TV standards in China ,
Roland A. Burger, Giovanni Iacovoni, Cliff Reader, Xiaoming Fu , Xiaodong Yang , and Wang Hui, Proceedings of ChinaCom 2007, Shanghai, China, Special Session on Digital Broadcasting and Mobile Convergence,
IEEE, August 2007.
Zusammenfassung lesen
This paper presents an updated overview of the different proposed standards on the market for mobile TV in China as of June 2007 and analyzes the different trade-offs, strengths and weaknesses. Furthermore the used video codecs are compared with special emphasis on the usage in mobile TV in China.
PDF [4370.5 kB]
Comparative Studies on Authentication and Key Exchange Methods for 802.11 Wireless LAN ,
Jun Lei , Xiaoming Fu , Dieter Hogrefe, and Jianrong Tan, Computers & Security, Volume 26, Issue 5, Pages 401-409,
Elsevier, ISSN 0167-4048, August 2007.
Zusammenfassung lesen
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.
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Method for carrying out a QoS-oriented handoff between a first and a second IP-based, especially mobile IPV6-based, communication path, between a mobile node (MN) and a correspondent node (CN) ,
Changpeng Fan, Andreas Festag, Xiaoming Fu , Cornelia Kapper, Holger Karl, Mirko Schramm, and Günter Schäfer (inventors), granted patent, No. AU2001276315,
August 2007.
Zusammenfassung lesen
The invention relates to a method for carrying out a QoS-oriented handoff between a first and a second IP-based, especially mobile IPv6-based, communication path, between a mobile node (MN) and a correspondent node (CN), the second communication path being part of a number of communication paths which can be accessed by the mobile node, with no, one, or a plurality of intermediate instances. The inventive method comprises at least the following steps: (a) a communication path is selected from the communication paths which can be accessed by the mobile node, as a second communication path; (b) a message (BU) is generated by the mobile node, said message containing at least one IP address which is associated with the mobile node on the basis of the selected communication path, and containing minimum quality of service requirements (QoS) in terms of the selected communication path; (c) the ability to meet at least the minimum quality of service requirements is controlled and optionally ensured by the individual intermediate instances through which the message passes successively, on the selected communication path and/or through the correspondent node. The message contains the minimum quality of service requirements for a communication from the mobile node to the correspondent node and/or vice versa. A handoff is automatically carried out between the first communication path and the second selected communication path, when at least the minimum quality of service requirements are met or the message is stopped. A notice is generated in an intermediate instance and/or in the correspondent node and is sent to the mobile node if the ability to meet the minimum quality of service requirements is not ensured.
Evaluating the Benefits of Introducing PMIPv6 for Localized Mobility Management ,
Jun Lei , and Xiaoming Fu , Technical Report No. IFI-TB-2007-02, Institute of Computer Science, University of Goettingen, Goettingen, Germany,
ISSN 1611-1044, June 2007.
Zusammenfassung lesen
Since recent years, it has been recognized that using global mobility protocol for managing localized mobility causes a number of problems, such as long registration delay. To overcome these problems, host-based and network-based localized mobility approaches have been proposed. Moreover, network based mobility management is more desirable since it requires no host software stack changes. Proxy Mobile IPv6 (PMIPv6) provides a solution for network-based mobility management that can avoid tunneling overhead over the air and support for hosts without an involvement in the mobility management.
We first review the localized mobility proposals and explore three major benefits that PMIPv6 can bring. In particular, we evaluate two aspects of the handover performance through a mathematical model for Fast Handovers for MIPv6 (FMIPv6), Hierarchical MIPv6 (HMIPv6), Fast handovers for HMIPv6 (F-HMIPv6) and PMIPv6. These analytical studies show that PMIPv6 may cause high handover latency if the local mobility anchor (LMA) is located far from the current mobility access gateway (MAG).
In this paper, we therefore propose an enhancement for PMIPv6, so-called fast handovers for PMIPv6 (F-PMIPv6) to further reduce the handover latency. The analysis result ascertains that F-PMIPv6 is a promising mobility scheme to efficiently manage the localized mobility.
PDF [184.3 kB]
A VLAN Ethernet Backplane for Distributed Network Systems ,
Lei Shi , and Peter Sjödin, IEEE Workshop on High Performance Switching and Routing (HPSR) 2007, New York, USA,
IEEE, May 2007.
Zusammenfassung lesen
In a network system, such as a router or a switch, it is difficult to achieve flexibility and performance at the same time. We propose an architecture that consists of network processors for packet processing and a VLAN-based Ethernet backplane for switching. This allows us to use flexible network processors for packet processing functions, and still exploit the cost-effectiveness of Ethernet to achieve switching capacity. We propose an architecture where we use VLAN tagging for internal traffic management, and also for distributed packet forwarding decisions between ingress and egress units. We describe our implementation of this system and report performance analysis, were we find that we can achieve near line rate performance in a system with Gigabit Ethernet ports, and that internal memory management is important for network processor performance.
PDF [62.6 kB]
ENABLE QoS Services for Large Operational IP Mobility Networks ,
Ivano Guardini, and Xiaoming Fu , Presented at the 1st OpenNet Workshop, Brussels, Belgium,
March 2007.
E2T: End-to-End Tunnelling Extension to Mobile IPv6 ,
Deguang Le , Xiaoming Fu , Xiaoyuan Gu, and Dieter Hogrefe, in Proceedings of the 4th IEEE Consumer Communications and Networking Conference (CCNC 2007), Las Vegas, Nevada, USA,
IEEE Communications Society, January 2007.
Zusammenfassung lesen
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 ,
Jun Lei , Xiaoming Fu , and Dieter Hogrefe, 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.
Zusammenfassung lesen
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]
Probe-Aided MulTCP: An Aggregate Congestion Control Mechanism ,
Fang-Chun Kuo , and Xiaoming Fu , Technical Report No. IFI-TB-2007-01, Institute of Computer Science, University of Goettingen, Goettingen, Germany,
ISSN 1611-1044, 2007.
Zusammenfassung lesen
A number of new application scenarios, e.g. mobile/wireless TCP proxies, edge to edge overlays, QoS provisioning and mass data transport, are calling for aggregate flow management. In this paper we show that applying a single flowshare to an aggregate flow will result in unfairness in the bandwidth sharing between the aggregate traffic and the background flows sharing the same bottleneck. To overcome this problem, we propose an aggregate congestion control mechanism, namely probe-aided MulTCP, which dynamically adjusts the congestion window loop to support multiple flowshares for an aggregate. The probe-aided MulTCP differs from existing works, such as MPAT, CP, MulTCP, in the following aspects. Firstly, our simulations show that against the traditional MulTCP the probe-aided MulTCP could maintain relatively stable, smooth and fair performance over a wide range of weight N in steady conditions as well as in varied congestion conditions. Secondly, an adjusting window loop is introduced to constantly probe the congestion situation and dynamically adjust the congestion window size for the newly arriving and leaving flows within the aggregate. This integration of congestion information improves the startup performance for new arriving flows, especially for short-lived ones. Thus, the probe-aided MulTCP is lightweight since only one extra probe window loop is used. Our extensive simulation studies show that with the probe-aided MulTCP, the improved performance and fairness will overweight the complexity caused by two congestion window loops.
PDF [665.8 kB]
2006
MobiArch'06 - Proceedings of the First ACM/IEEE International Workshop on Mobility in the Evolving Internet Architecture ,
Katherine Guo, Xiaoming Fu , and Jon Crowcroft (editors), San Francisco, CA, USA,
ACM Press, ISBN 1-59593-566-5, December 2006.
Implementation and Evaluation of the Interaction between Host Identity Protocol and Session Initiation Protocol ,
Steffen Wagner , Master's thesis, No. ZFI-BM-2006-42, Center for Informatics, University of Goettingen, Germany,
ISSN 1612-6793, December 2006.
Zusammenfassung lesen
The Session Initiation Protocol (SIP) enables a pair of user agents to establish and maintain sessions. The recent proposed Host Identity Protocol (HIP) addresses the issue of multi-homing, readdressing and mobility by introducing an additional layer between the network and transport layers. The scope of this thesis is to implement the concept of exchanging the Host Identities (or Host Identity Tags) used in HIP as part of the initial SIP exchange, thus enabling the real-time communications in nomadic environments.
PDF [289.2 kB]
Beyond QoS Signaling: a Generic IP Signaling Framework ,
Xiaoming Fu , Hannes Tschofenig , and Dieter Hogrefe, Computer Networks, Volume 50, Issue 17, pages 3416-3433,
Elsevier, December 2006.
Zusammenfassung lesen
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 todays 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 [602.3 kB]
A Survey of Handover Algorithms in DVB-H ,
Xiaodong Yang , Jani Väre, and Thomas J. Owens, IEEE Communications Surveys & Tutorials, 8(4): 16-29,
IEEE, ISSN: 1553-877X, December 2006.
Zusammenfassung lesen
Digital Video Broadcasting for Handhelds (DVB-H) is a standard for broadcasting IP Datacast (IPDC) services to mobile handheld terminals. Based on the DVB-T standard, DVB-H adds new features such as time slicing, MPE-FEC, in-depth interleavers, mandatory cell id identifier,
optional 4K-modulation mode and the use of 5 MHz bandwidth in addition to the usually used 6, 7, or 8 MHz raster. IPDC over DVB-H is proposed for ETSI to complement the DVB-H standard by combining IPDC and DVB-H in an end-to-end system. Handover in such unidirectional broadcasting
networks is a novel issue. In the last few years since the birth of DVB-H technology, great attention has been given to the performance analysis of DVB-H mobile terminals. Handover is one of the main research topics for DVB-H in mobile scenarios. Better reception quality and greater power efficiency are considered to be the main targets of handover
research for DVB-H. New algorithms for different handover stages in DVB-H have been the subject of recent research and are currently being studied. Further novel algorithms need to be designed to improve the mobile reception quality.
This article provides a comprehensive survey of the handover algorithms in DVB-H. A systematic evaluation and categorization approach is proposed based on the problems the algorithms solve and the handover stages being focused on. Criteria are proposed and analyzed to facilitate designing better handover algorithms for DVB-H that have been identified from the research conducted by the authors.
PDF [260.1 kB]
Prototyping and Testing of GONE - GIST Overlay Networking Extension ,
Jan Demter , Bachelor's thesis, No. ZFI-BM-2006-37, Center for Computer Science, University of Goettingen, Germany,
ISSN 1612-6793, November 2006.
Zusammenfassung lesen
This thesis provides an implementation of the GIST Overlay Network Extension (GONE) and its initial performance testing. GONE is an overlay network built upon the General Internet Signaling Transport (GIST) and the Stream Control Transmission Protocol (SCTP). GIST enables GONE to automatically build an overlay along a path in an IP-network with GONE-aware routers. Each GONE-aware hop forwards traffic to the next hop via an SCTP connection, making GONE resilient to path failures due to SCTP’s failover mechanism. Protection against DoS-attacks is employed by using a per-packet capability based authentication. The thesis investigates how the functionality offered by GIST can be used in implementing a path overlay. Problems with the concept of GONE surfacing during implementation and testing are pointed out and possible solutions or hints for further research and testing are given.
PDF [756.7 kB]
From Resource Reservation to Extensible IP Signaling ,
Xiaoming Fu , Habilitation Thesis, Mathematische Fakultaet, Universitaet Goettingen, Goettingen, Germany, 146 pages,
October 2006.
Dynamic Mesh-based overlay Multicast Protocol (DMMP) ,
Jun Lei , Xiaoming Fu , and Dieter Hogrefe, Internet Research Task Force, Internet draft (draft-lei-samrg-dmmp-01), work in progress, Scalable Adaptive Multicast (SAM) Research Group,
October 2006.
Zusammenfassung lesen
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 ,
Hannes Tschofenig , and Xiaoming Fu , International Journal of Internet Protocol Technology, Volume 1, No. 4, pages 271-282,
InderScience Publishers, ISSN 1743-8209, August 2006.
Zusammenfassung lesen
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 ,
Niklas Steinleitner , Henning Peters , Xiaoming Fu , 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.
Zusammenfassung lesen
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 ,
Jun Lei , Xiaoming Fu , and Dieter Hogrefe, Technical Report No. IFI-TB-2006-05, Institute of Computer Science, University of Goettingen, Germany,
ISSN 1611-1044, July 2006.
Zusammenfassung lesen
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 , IEE Proceedings Communications,
ISSN 1350-2425, Volume 153, Issue 3, pages 365-375, June 2006.
Zusammenfassung lesen
The notion of soft state has been introduced in packet-switched networks to achieve particular services for end-to-end communications, such as quality-of-service provisioning and configuration of stateful packet filters. Protocols built upon soft state principles were believed to be simple, however in practice they are far more complex. An important issue with such protocols is to ensure their operations to be error-free and deadlock-free. In the paper the use of formal techniques is proposed, specifically, Specification and Description Language (SDL) and Message Sequence Charts (MSCs), for modelling, analysis and validation of soft-state protocols. Based on a general state management system that identifies their most representative behaviour, an extensive study on modelling and validating soft-state protocols with SDL/MSCs is presented, and it is shown that design flaws and ambiguity introduced in informally specified, textual protocols can be avoided if a protocol is formally modelled.
PDF [341.0 kB]
Incorporating digital repeaters into the soft handover standard in digital video broadcasting for handhelds ,
Xiaodong Yang , Yong-Hua Song, Thomas J. Owens, John Cosmas, and Takebumi Itagaki, International Journal of Services and Standards, 2(3): 238 - 256,
InderScience Publishers, ISSN 1740-8849, June 2006.
Zusammenfassung lesen
Digital Video Broadcasting for Handhelds (DVB-H) is a standard for broadcasting IP data to portable devices. This paper proposes and analyses the Repeater-Aided Soft Handover (RA_handover) algorithm for a DVB-H receiver with Multiple InputMultiple Output (MIMO) antennas and presents the benefits of implementing the RA_handover compared with a handover process without repeaters. Simulation models are developed to analyse the RA_handover approach. It is shown that the RA_handover could greatly improve the quality of service and consume much less front-end battery power than the handover method without repeaters. This paper also provides valuable outcomes for service providers and standard policymakers.
PDF [569.4 kB]
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.
Zusammenfassung lesen
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]
Overhead and Performance Study of the General Internet Signaling Transport (GIST) Protocol ,
Xiaoming Fu , Henning Schulzrinne, Hannes Tschofenig , Christian Dickmann , and Dieter Hogrefe, IEEE INFOCOM 2006, Bacelona, Spain,
IEEE, April 2006.
Zusammenfassung lesen
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]
Comparison Studies between Pre-Shared and Public Key Exchange Mechanisms for Transport Layer Security ,
Fang-Chun Kuo , Hannes Tschofenig , Fabian Meyer , and Xiaoming Fu , 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.
Zusammenfassung lesen
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]
Analysis of NAT Approaches and Explicit Signaling for NAT Traversal ,
Henning Peters , Bachelor's thesis, No. ZFI-BM-2006-09, Zentrum fuer Informatik, Universitaet Goettingen,
ISSN 1612-6793, March 2006.
Zusammenfassung lesen
Network Address Translation (NAT) provides a solution for IPv4 address depletion and Internet scalability problems at large. NAT has since been unexpectedly popular, and it is in wide use today, especially in home and small office environments. Unfortunately, it has major drawbacks, most fundamental is the maintenance of states inside the network, challenging the Internets end-to-end principle.
This thesis analyzes these very promising NAT approaches, and tries to compare the approaches with each other. Furthermore, an applicability statement for implicit and explicit NAT configuration is given and an implementation of NAT/Firewall NSLP proves the feasibility of an yet uncommon explicit signaling approach.
PDF [430.0 kB]
Principles and Experiments of Explicit Delay Control ,
Xiaoyuan Gu, Dirk Markwardt, Lars Wolf, and Xiaoming Fu , Proceedings of IEEE Consumer Communications and Networking Conference (CCNC'06), Las Vegas, USA,
IEEE, January 2006.
Zusammenfassung lesen
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]
Comparison Studies between Pre-Shared Key and Public Key Exchange Mechanisms for Transport Layer Security (TLS) ,
Fang-Chun Kuo , Hannes Tschofenig , Fabian Meyer , and Xiaoming Fu , Technical Report No. IFI-TB-2006-01, Institute of Computer Science, University of Göttingen, Göttingen, Germany,
ISSN 1611-1044, 2006.
Zusammenfassung lesen
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]
A Review of Mobility Support Paradigms for the Internet ,
Deguang Le , Xiaoming Fu , and Dieter Hogrefe, IEEE Communications Surveys and Tutorials, Volume 8, No. 1, First Quarter, pages 38-51,
IEEE, ISSN 1553-877X, 2006.
Zusammenfassung lesen
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]
Symbol-Flipping Based Decoding of Generalized Low-Density Parity-Check Codes Constructed over GF(q) ,
Fang-Chun Kuo , and Lajos Hanzo, Proc. of the IEEE Wireless Communications and Networking Conference 2006, Las Vegas, NV USA, IEEE,
2006.
Zusammenfassung lesen
An efficient symbol-flipping based decoding algorithm designed for nonbinary Generalized Low-Density Parity-Check (GLDPC) codes is proposed. By extending the concept of the Weighted Bit Flip Voting (WBFV) algorithm designed for binary Hamming-code based GLDPC codes, the symbol-flipping
decoding algorithm can be beneficially employed for decoding the family of GLDPC codes constructed from nonbinary constituent codes, such as nonbinary Bose Chaudhuri Hocquenghem (BCH) codes or Reed Solomon (RS) codes. The simulation results demonstrate that improvements of 1 dB and 2.7 dB are achieved by the proposed coding scheme in comparison to the more conventional binary GLDPC codes using the WBFV decoding algorithm, when using the Galois Field GF(32) for communicating over AWGN and uncorrelated Rayleigh fading channels, respectively.
PDF [223.3 kB]
Generalized Low-Density Parity-Check Coding Aided Multilevel Codes ,
Ronald Y.S. Tee, Fang-Chun Kuo , and Lajos Hanzo, Proc. of the IEEE VTC2006-Spring, Melbourne, Australia,
2006.
Zusammenfassung lesen
Classic Low-Density Parity-Check (LDPC) codes have recently been used as component codes in Multilevel Coding (MLC) due to their impressive BER performance as well as owing to their flexible coding rates. In this paper, we proposed a Multilevel Coding invoking Generalized Low-Density Parity-Check (GLDPC) component codes, which is capable of outperforming the classic LDPC component codes at a reduced decoding latency, when communicating over AWGN and uncorrelated Rayleigh fading
channels.
PDF [117.5 kB]
Multilevel Generalized Low-Density Parity-Check Codes ,
Ronald Y.S. Tee, Fang-Chun Kuo , and Lajos Hanzo, IEE Electronics Letters, Vol. 42, Issue 3, Pages 167 - 168,
ISSN: 0013-5194, 2006.
Zusammenfassung lesen
Multilevel coding invoking generalised low-density parity-check component codes is proposed, which is capable of outperforming the classic low-density parity check component codes at a reduced decoding latency.
PDF [86.0 kB]
2005
Implementation and Performance Testing of the NAT/FW NSIS Signaling Layer Protocol ,
Niklas Steinleitner , Master's thesis No. ZFI-BM-2005-41, Center for Informatics, University of Goettingen, Germany,
ISSN 1612-6793, December 2005.
Zusammenfassung lesen
This thesis describes the first implementation and performance testing of the path-coupled signaling protocol for Network Address Translator (NAT) and firewall configuration within an extensible IP signaling framework developed by the IETF Next Steps in Signaling (NSIS) working group, called the NAT/FW NSIS Signaling Layer Protocol (NAT/FW NSLP). This new protocol allows hosts to signal along a data path to configure NATs and firewalls according to the data flow needs.
In comparison with prior works on firewall signaling, one major contribution of this thesis is that it presents a detailed performance study of the NAT/FW NSLP protocol through an experimental testbed. The performance results show that implementation can support firewall signaling for up to tens of thousands of flows in parallel, and scale well. Besides the limitation due to the low-end PC hardware, the overall performance bottleneck is found to lie in the utilized firewall implementation, not depending on the NAT/FW NSLP implementation.
PDF [4063.9 kB]
Formal Specification and Security Verification of the IDKE Protocol using FDR Model Checking ,
Rene Soltwisch, Florian Tegeler , and Dieter Hogrefe, Proceedings of the 13th IEEE International Conference on Networks (ICON),
IEEE, ISBN 1-4244-0000-7, November 2005.
Zusammenfassung lesen
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 an initiated 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 security properties, 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 between two access routers.
PDF [1658.7 kB]
Architectural Thoughts and Requirements Considerations on Video Streaming over the Internet ,
Jun Lei , Ingo Juchem , Xiaoming Fu , and Dieter Hogrefe, Technical Report No. IFI-TB-2005-06, Institute of Computer Science, University of Goettingen, Germany,
ISSN 1611-1044, November 2005.
Zusammenfassung lesen
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 ,
Henning Schulzrinne, Hannes Tschofenig , Xiaoming Fu , and Jochen Eisl, Technical Report No. TB-IFI-2005-07, Institute of Computer Science, University of Goettingen, Germany,
ISSN 1611-1044, November 2005.
Zusammenfassung lesen
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 ,
Hannes Tschofenig , Henning Schulzrinne, Robert Hancock, Andrew McDonald, and Xiaoming Fu , Technical Report No. TB-IFI-2005-08, Institute of Computer Science, University of Goettingen, Germany,
ISSN 1611-1044, November 2005.
Zusammenfassung lesen
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 , Henning Schulzrinne, Attila Bader, Dieter Hogrefe, Cornelia Kappler, Georgios Karagiannis, Hannes Tschofenig , and Sven Van den Bosch, IEEE Communications Magazine, Internet Technology Series, 43(10): 133-141,
IEEE, October 2005.
Zusammenfassung lesen
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 ,
Xiaoyuan Gu, Xiaoming Fu , 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.
Zusammenfassung lesen
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]
An Implementation and Evaluation of the General Internet Signaling Transport Protocol ,
Christian Dickmann , Bachelor's thesis, No. ZFI-BM-2005-26, Zentrum fuer Informatik, Universitaet Goettignen,
ISSN 1612-6793, September 2005.
Zusammenfassung lesen
The General Internet Signaling Transport (GIST) Protocol is currently being developed by the IETF Next Steps in Signaling (NSIS) working group. It is the base protocol supporting a variety of signaling applications to be run on top of it. This thesis targets at validating the GIST specification as well as examining the design of an implementation. Therefore, I discuss the major design aspects of the GIST implementation that we developed at the University of Goettingen and evaluate it with respect to CPU and resource utilization.
The performance experiments show that the implementation performs reasonable even under heavy load. In general the implementation shows that the specification is very mature and that the main features work very well.
PDF [729.8 kB]
Fast Seamless Handover Scheme and Cost Performance Optimization for Ping-Pong Type of Movement ,
Zongkai Yang, Yuming Wang, Dasheng Zhao, Jianhua He, and Xiaoming Fu , Proceedings of the 16th Annual IEEE International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC 2005), Berlin, Germany,
IEEE, September 2005.
Zusammenfassung lesen
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 ,
Tseno Tsenov, Hannes Tschofenig , Xiaoming Fu , and Eckhart Koerner, 1st IEEE 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), Pages 224-235,
IEEE Computer Society Press, September 2005.
Zusammenfassung lesen
One of the key requirements of todays 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 ,
Deguang Le , Xiaoming Fu , Xiaoyuan Gu, and Dieter Hogrefe, Technical Report No. IFI-TB-2005-05, Institute of Computer Science, University of Göttingen, Göttingen, Germany,
ISSN 1611-1044, September 2005.
Zusammenfassung lesen
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.
Zusammenfassung lesen
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]
Review of CasperFDR Analysis of the IDKE Protocol ,
Florian Tegeler , and Rene Soltwisch, Technical Report No. IFI-TB-2005-04, Institute of Computer Science, University of Göttingen, Germany,
ISSN 1611-1044, June 2005.
RSVP Standards Today and the Path Towards a Generic Messenger ,
Xiaoming Fu , and 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, pages 385-387,
Springer Verlag, ISBN 3-540-26294-6, June 2005.
Zusammenfassung lesen
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 ,
Constantin Werner, Xiaoming Fu , and Dieter Hogrefe, 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.
Zusammenfassung lesen
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 , and 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.
Zusammenfassung lesen
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 ,
Jukka Manner, and Xiaoming Fu , Request for Comment (RFC) 4094,
Internet Engineering Task Force, May 2005.
Zusammenfassung lesen
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]
Video Image-based Intelligent Architecture for Human Motion Capture ,
Jun Lei , Dieter Hogrefe, and Jianrong Tan, ICGST International Journal on Graphics, Vision and Image Processing (GVIP), Volume 5, Issue 5, Pages 11-16,
ISSN 1687-398X, May 2005.
Zusammenfassung lesen
Die Studie über die menschliche Bewegung ist ein faszinierendes Subjekt in der Computer-Vision, und sie entwickelte sich im Laufe von vielen Jahren. Nach der traditionellen Methode werden Maschinenanlagen, elektromagnetische Ausstattungen, Akustik, Optik, Grafik usw. benutzt, um die menschliche Bewegung zu erfassen. In dieser Methode gibt es aber manche Mängel, z.B. hohe Kosten, die Beschränkung vom Sensor und die Lokalisierung im Sportsbereich, und wegen der verschiedenen Vorsätze und Bedingungen hat es keine beständigen Maßtäbe. Am wichtigsten ist, dass eine Person die langweilige und sterile Arbeit für Beobachtung machen muss. Manchmal kann dieses manuell bediente Engagement mit dem Wunsch nach erfassenden Daten ohne überflüssige oder nutzlose Informationen nicht übereinstimmen. Die Charaktereigenschaft des Videos stellt neue Chancen und Änderungen für die menschliche Bewegungserfassung dar. Der vorliegende Atikel zeigt uns eine wirkliche Architektur der Bewegungserfassung des Menschen, die die Vergleiche des Video-Images und die Ausdrücken des Beobachtungsbereichs benutzt. Dann ist eine effektive Methode für Datenspeicherung. Außerdem verwertet die Architektur in GOLF-Sportsbildung gut als ein Beispiel.
PDF [286.2 kB]
Performance Analysis of the TCP/IP Stack of Linux Kernel 2.6.9 ,
Jan Demter , Christian Dickmann , Henning Peters , Niklas Steinleitner , and Xiaoming Fu , Technical Report No. IFI-TB-2005-03, Institute of Computer Science, University of Göttingen, Germany,
ISSN 1611-1044, April 2005.
Zusammenfassung lesen
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]
Implementation of a Signaling Router for the Euro6IX Premium Service ,
Ingo Juchem , Master's thesis No. ZFI-BM-2005-03, Center for Informatics, University of Goettingen, Germany,
ISSN 1612-6793, March 2005.
Zusammenfassung lesen
In order to enable Diffentiated Services for multimedia applications in IP-based networks, there is a need to signal QoS resource requirements to the edges of a DiffServ network. This thesis implements on a soft state approach of QoS signaling for SIP-based applications in DiffServ network edges, taking authentication and authorization into account. We also use per-flow policing and Priority Promotion Scheme (PPS) for traffic control in access routers, without introducing any control state in the core network.
PDF [769.1 kB]
A Review of Mobility Support Paradigms for the Internet ,
Deguang Le , Xiaoming Fu , and Dieter Hogrefe, Technical Report No. IFI-TB-2005-01, Institute of Computer Science, University of Göttingen,
ISSN 1611-1044, January 2005.
Zusammenfassung lesen
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 ,
Rene Soltwisch, Xiaoming Fu , Dieter Hogrefe, and Sathya Narayanan, Proceedings of 12th IEEE International Conference on Networks (ICON 2004), Singapore, pp. 463-469,
ISBN 0-7803-8783-X, November 2004.
Zusammenfassung lesen
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.
PDF [263.1 kB]
QoS and Security in 4G Networks ,
Xiaoming Fu , Dieter Hogrefe, Sathya Narayanan, and Rene Soltwisch, Proceedings of the 1st CIC/IEEE Global Mobile Congress (GMC 2004), Shanghai, China, pp. 117-122,
October 2004.
Zusammenfassung lesen
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.
PDF [369.9 kB]
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.
Zusammenfassung lesen
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.
PDF [111.3 kB]
Modeling Soft State Protocols with SDL ,
Xiaoming Fu , and Dieter Hogrefe, Technical Report No. IFI-TB-2004-02, Institute of Computer Science, University of Göttingen, Germany,
ISSN 1611-1044, August 2004.
Zusammenfassung lesen
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.
PDF [112.1 kB]
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 of Computer Science, University of Göttingen, Germany,
ISSN 1611-1044, April 2004.
Zusammenfassung lesen
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.
PDF [416.3 kB]
A Prototype Implementation and Experimental Test of the Messaging Layer of CASP: a General-Purpose Internet Signaling Protocol ,
Sebastian Willert , Bachelor's thesis, No. ZFI-BM-2004-01, Zentrum fuer Informatik, Universitaet Goettignen,
ISSN 1612-6793, February 2004.
Zusammenfassung lesen
Signaling has become necessary for allowing IP-based networks to manage states in network nodes. However, existing protocols cannot deliver desired signaling services needed for large-scale deployment. The Cross-Application Signaling Protocol (CASP), a general-purpose signaling protocol, introduces a new approach to overcome the limitations of these protocols. This thesis reports a prototype implementation of the CASP transport layer protocol using TCP as the underlying transport protocol, and studies the feasibility of the modular design. The behavior of this implementation has been analyzed through an experimental testbed. Performance results show that the memory and CPU consumption of the implementation are low even under heavy signaling loads; the round trip time of signaling messages is also acceptable. Although further work will be necessary, critical design choices in CASP have been proved to be feasible.
PDF [719.9 kB]
Design and Implementation of a Scout Daemon for CASP ,
Fabian Meyer , Bachelor's thesis, No. ZFI-BM-2004-02, Zentrum fuer Informatik, Universitaet Goettignen, ISSN 1612-6793,
February 2004.
Zusammenfassung lesen
The CASP protocol is a general signaling protocol working on top of existing transport protocols such as TCP, UDP, SCTP or raw IP. It provides a framework for applications that need signaling. Applications include first of all QoS.
This thesis describes the design, implementation and testing of a scout daemon for CASP. The task of this daemon is to provide the main CASP daemon with a service, that can effectively discover the next CASP-aware hop on the path to a given destination. The experimental results show that the scout protocol implementation is stable, feasible and fast.
PDF [368.9 kB]
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.
Zusammenfassung lesen
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.
PDF [71.8 kB]
Prototype Implementation and Performance Evaluation of a QoS-Conditionalized Handoff Scheme for Mobile IPv6 Networks ,
Axel Neumann, Xiaoming Fu , 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.
Zusammenfassung lesen
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.
PDF [87.7 kB]
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.
Zusammenfassung lesen
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.
PDF [39.6 kB]
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.
Zusammenfassung lesen
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.
PDF [75.9 kB]
CASP - Cross-Application Signaling Protocol ,
Henning Schulzrinne, Hannes Tschofenig , Xiaoming Fu , 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), March 2003.
Zusammenfassung lesen
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.
PDF [103.1 kB]
Towards RSVP Lite: Light-weight RSVP for Generic Signaling ,
Xiaoming Fu , and 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.
Zusammenfassung lesen
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.
PDF [42.9 kB]
Design of CASP - a Technology Independent Lightweight Signaling Protocol ,
Henning Schulzrinne, Xiaoming Fu , Cornel Pampu, and Cornelia Kappler, Proceedings of the 1st International Workshop on Inter-domain Performance and Simulation (IPS 2003), Salzburg, Austria,
February 2003.
Zusammenfassung lesen
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.
PDF [48.2 kB]
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.
Zusammenfassung lesen
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.
PDF [335.7 kB]
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.
Zusammenfassung lesen
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.
Zusammenfassung lesen
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]
2000
Admission Control for Providing Statistical QoS in High-Speed Networks ,
Xiaoming Fu , and Yaoxue Zhang, Acta Electronica Sinica, 28(10): 82-85,
October 2000.
Achieving QoS Request Efficiently for the Internet Using RSVP Tunnels ,
Guoqiang Guo, Yaoxue Zhang, and Xiaoming Fu , Journal of Computer Research and Development, 37(1):55-60,
, January 2000.
