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2009
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 (to appear),
April 2009.
Read abstract
The General Internet Signaling Transport (GIST) protocol is currently being developed as the base protocol component in the IETF Next Steps In Signaling (NSIS) protocol stack to support a variety of signaling applications. 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]
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 1420066625, February 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.
Read abstract
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.
Read abstract
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]
A Cross-Layer Approach for Improving TCP Performance in Mobile Environments ,
Deguang Le , Xiaoming Fu , and Dieter Hogrefe, Wireless Personal Communications,
Springer Verlag, October 2008.
Read abstract
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 [288.3 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.
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,
IEEE, August 2008.
Read abstract
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.
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.
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.
Read abstract
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.
Read abstract
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]
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.
Read abstract
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.
Read abstract
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.
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.
Read abstract
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.
Read abstract
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.
Read abstract
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.
Read abstract
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.
Read abstract
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]
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,
February 2008.
Read abstract
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,
February 2008.
Read abstract
The General Internet Signaling Transport (GIST) protocol currently uses TCP or TLS over TCP for connection mode operation. This document describes the usage of GIST over the Stream Control Transmission Protocol (SCTP). The use of SCTP can take the advantage of features provided by SCTP, namely streaming-based transport, support of multiple streams to avoid head of line blocking, and the support of multi-homing to provide network level fault tolerance. Additionally, the support for the Partial Reliability Extension of SCTP is discussed.
TXT [22.0 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, January 2008.
Read abstract
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]
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.
Read abstract
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]
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.
Read abstract
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.
Read abstract
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.
Read abstract
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.
Read abstract
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.
Read abstract
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 identifi cation.
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 specifi cations 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.
PDF [1847.2 kB]
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.
Read abstract
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.
Read abstract
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.
Read abstract
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.
PDF [436.4 kB]
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.
Read abstract
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.
Read abstract
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.
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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.
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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.
