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IEEE Workshop on High Performance Switching and Routing

作者： Arthur Mutter Institute of Communication Networks and Computer Engineering (IKR) University of Stuttgart Stuttgart Germany

High speed Internet routers and switches require fast packet buffer to hold packets during times of congestion. These buffers usually use a memory hierarchy that consist of expensive but fast SRAM and cheap but slow DRAM to meet both, speed and capacity requirements. A challenge building these packet buffers is to provide deterministic bandwidth guarantee under any traffic condition. We propose a novel hybrid packet buffer architecture with parallel DRAMs. Our approach reduces the amount of required SRAM compared to state-of-the-art architectures significantly, e. g., the tail SRAM by 47% for a 100Gbps line card using DDR3 SDRAM. Our architecture also applies packet aggregation and thereby minimizes the required DRAM and SRAM bandwidth and eliminates fragmentation. We are currently implementing the architecture on an FPGA and provide first results.

关键词： Bandwidth Round robin Memory management Resource management SDRAM

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On optimal communication spanning trees in embedded Ethernet networks

On optimal communication spanning trees in embedded Ethernet...

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IEEE International Workshop on Factory communication Systems (WFCS)

作者： Jörg Sommer Institute of Communication Networks and Computer Engineering lKR University of Stuttgart Stuttgart Germany

In network design, the Optimal communication Spanning Tree (OCST) problem is to find a spanning tree that connects the network entities and satisfies their communication requirements with minimal total cost. In an embedded Ethernet network, we organize the full duplex links into bundles and install these bundles into ducts. The traditional OCST problem does not take into account this fact. In this paper, we introduce a mathematical model of the communication cost of an embedded Ethernet network. We propose novel algorithms to find an OCST. Their principle idea is that they iteratively examine a set of neighboring trees that differ in one duct and choose the tree with the lowest cost. Finally, we evaluate the performance of the algorithms in terms of the quality of the solution found as well as the running time.

关键词： Ethernet networks Costs Ducts Wires Iterative algorithms Local area networks Bandwidth Wiring Mathematical model Virtual manufacturing

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Fine-Grained Parallel Compacting Garbage Collection through Hardware-Supported Synchronization

Fine-Grained Parallel Compacting Garbage Collection through ...

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International Conference on Parallel Processing Workshops (ICPPW)

作者： Oswin Horvath Matthias Meyer Institute of Communication Networks and Computer Engineering Universität Stuttgart Stuttgart Germany

Parallel garbage collection seeks to exploit the inherent parallelism of graph tracing by evenly distributing the set of objects in the heap among all available processing resources. Any straightforward implementation, however, suffers from prohibitive overheads since each access to the worklist of objects and to the objects themselves needs to be protected by synchronization, especially so in the case of compacting collectors. For this reason, known parallel collectors sacrifice a great deal of work distribution granularity and scalability to keep the synchronization costs acceptable. In this paper, we present a case study of a different approach. Our parallel compacting collector is based on Cheney's copying algorithm, employs a single worklist and distributes garbage collection work on an object-by-object basis. This way, it achieves well balanced work distribution and good scalability. To solve the synchronization problem, we introduce a low-cost multi-core garbage collection coprocessor and take advantage of hardware-supported synchronization. We built an FPGA-based prototype with a single-core main processor supported by a multi-core garbage collection coprocessor. Measurement results show that an 8-core garbage collection coprocessor decreases the duration of garbage collection cycles by a factor of up to 7.4, while a 16-core configuration still achieves a factor of up to 12.1.

关键词： Synchronization Registers Heuristic algorithms Coprocessors Partitioning algorithms Data structures Memory management

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A framework for model-driven proposal and evaluation of TABAC strategies

A framework for model-driven proposal and evaluation of TABA...

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Future Network and Mobile Summit

作者： Jochen Kögel David Lutz Marc Barisch Yongzheng Liang University of Stuttgart Institute of Communication Networks and Computer Engineering Germany University of Stuttgart Computing Center Germany

Trust, Accounting, Billing, Auditing and Charging (TABAC) are crucial functions of productive IT and telecommunication systems. However, they are often not considered in early stages of development, but have considerable impact on commercial success at later stages. On the one hand, these functions are costly to be added after having a running prototype. On the other hand, they should not be burdens in early development stages. In order to solve this dilemma, we propose a framework for model-driven proposal and evaluation of TABAC strategies. This framework allows both: evaluating the possibilities to add TABAC functions at an early development stage and adding TABAC strategies to running prototypes by using existing interfaces and applying general models from a model pool. The framework not only proposes suitable strategies based on capabilities and requirements of the existing system. Moreover, it aims at instantiating the TABAC functions in a runtime environment for feeding them with real data from the existing system. This outstanding feature allows compiling a proposal for the best suiting strategy based on realistic interactions with the prototype.

关键词： Prototypes Runtime Data models Adaptation model Protocols Proposals Monitoring

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NETWORKING 2010: 9th International IFIP TC 6 Networking Conference Chennai, India, May 11-15, 2010 Proceedings 9

NETWORKING 2010: 9th International IFIP TC 6 Networking Conf...

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9th International IFIP TC 6 Networking Conference, NETWORKING 2010

作者： Crovella, Mark Feeney, Laura Marie Rubenstein, Dan Raghavan, S.V. Boston University Department of Computer Science 111 Cummington St. BostonMA United States Swedish Institute of Computer Science Communication Networks and Systems Laboratory Box 1263 Kista Sweden Columbia University 450 Computer Science Bldg. MC 0401 1214 Amsterdam Ave NewYorkNY United States Indian Institute of Technology Madras Department of Computer Science and Engineering Chennai India

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A Novel Sampling Method for the Spatial Frequencies of Sinusoid-Based Shadowing Models

A Novel Sampling Method for the Spatial Frequencies of Sinus...

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IEEE Conference on Vehicular Technology (VTC)

作者： Siegfried Klein Serkan Uygungelen Christian M. Mueller Bell Laboratories Germany Stuttgart Germany Institute of Communication Networks and Computer Engineering Universität Stuttgart Stuttgart Germany

ISBN: (纸本)9781424425181;9781424425198

Careful modeling of the radio channel characteristics is an important issue for system level simulations. While a number of detailed path loss, shadowing and fast fading models can be found in literature, many of them entail large computational efforts and hence lead to long simulation times, or require huge amounts of memory. In this paper, we focus on shadowing models with two-dimensional correlation properties. We present handover performance evaluations as a use case from which requirements to the modeling of the shadow fading are derived. For different implementations of the shadow fading in system level simulations, we discuss their pros and cons and then focus on the sum of sinusoid model proposed by Cai and Giannakis. Our main contribution lies in a new frequency sampling method to determine the coefficients of the sinusoidal waveforms. We show that this new method, denoted as Power Sampling Method (PSM), allows for a significant reduction of the number of sinusoids while the correlation properties of the shadow fading channel are preserved.

关键词： Sampling methods Frequency Shadow mapping Fading Computational modeling Power system modeling Radio propagation communication networks computer networks computer simulation

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Adaptive fairness control for a proportional fair LTE scheduler

Adaptive fairness control for a proportional fair LTE schedu...

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IEEE International Symposium on Personal, Indoor and Mobile Radio communications (PIMRC)

作者： Magnus Proebster Christian M. Mueller Hajo Bakker Institute of Communication Networks and Computer Engineering Universität Stuttgart Stuttgart Germany Alcatel-Lucent Bell Laboratories Stuttgart Germany

In cellular OFDMA networks, there exists a fundamental trade-off between the achievable cell capacity and the degree of fairness among the users in the cell. Several scheduling algorithms have been proposed which try to balance this tradeoff. The parameterization of these scheduling algorithms to achieve a certain desired fairness level is non-trivial. We show that the optimal fairness parameter settings depend on the system state, such as the current cell load. Our main contribution is a design of a self-optimizing scheduler architecture which includes a controller element that dynamically adjusts the fairness parameters of the scheduler. We demonstrate that with this design, an operator-defined reference fairness level is maintained in scenarios with fluctuating load and thus cell throughput can be improved. It is applicable for a class of proportional fair scheduling algorithms and can be adapted to other algorithms allowing to influence the fairness level.

关键词： Variable speed drives Signal to noise ratio Quality of service Bandwidth Interference

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Truly random number generation based on measurement of phase noise of a laser

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Physical Review E 2010年第5期81卷 051137-051137页

作者： Hong Guo Wenzhuo Tang Yu Liu Wei Wei CREAM Group State Key Laboratory of Advanced Optical Communication Systems and Networks (Peking University) and Institute of Quantum Electronics School of Electronics Engineering and Computer Science Peking University Beijing 100871 China

We present a simple approach to realize truly random number generator based on measuring the phase noise of a single-mode vertical cavity surface emitting laser. The true randomness of the quantum phase noise originates from the spontaneous emission of photons and the random bit generation rate is ultimately limited only by the laser linewidth. With the final bit generation rate of 20 Mbit/s, the truly random bit sequence guaranteed by the uncertainty principle of quantum mechanics passes the three standard randomness tests (ENT, Diehard, and NIST Statistical Test Suites). Moreover, a continuously generated random bit sequence, with length up to 14 Gbit, is verified by two additional criteria for its true randomness.

关键词： Phase noise

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Analysis of internet connectivity and number of isolated clients in finite one-dimensional multihop wireless access networks

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Tamkang Journal of Science and engineering 2010年第4期13卷 443-454页

作者： Hsu, Chun-Yen Wang, Shun-Te Wu, Jean-Lien C. Networks and Multimedia Institute Institute for Information Industry Taipei 105 Taiwan Department of Electronic Engineering Hwa Hsia Institute of Technology Taipei 235 Taiwan Department of Computer and Communication Engineering St. John's University Tamsui 251 Taiwan

Multihop wireless access networks, where clients can access the Internet through Internet gateways by direct or multihop transmissions, are potential for future wireless data services and vehicular network applications. In the context of multihop transmissions, less number of gateways is required for Internet access while a certain level of Internet connectivity still holds. In this paper, we investigate the Internet connectivity, which is the probability that all clients are Internet-reachable, in one-dimensional multihop wireless access networks. We show the relationship between the Internet connectivity and the deployment of Internet gateways. We also investigate the mean number of isolated clients, who are not Internet-reachable, in a multihop wireless access network. These results are useful for network operators to deploy Internet gateways, manage clients and design protocols for future vehicular network applications. The theoretical results are corroborated through extensive simulations.

关键词： Vehicular ad hoc networks

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Security and privacy enablers for future identity management systems

Security and privacy enablers for future identity management...

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作者： Barisch, Marc Torroglosa Garcia, Elena Lischka, Mario Marques, Rodolphe Marx, Ronald Matos, Alfredo Perez Mendez, Alejandro Scheuermann, Dirk University of Stuttgart Institute of Communication Networks and Computer Engineering Pfaffenwaldring 47 70569 Stuttgart Germany University of Murcia Murcia Spain NEC Laboratories Europe Heidelberg Germany Instituto de Telecomunicações de Aveiro Universidade de Aveiro Aveiro Portugal Darmstadt Germany

ISBN: (纸本)9781905824182

In recent years, Identity Management (IdM) has gained a lot of attention in industry, standardisation and academia. In particular, a couple of research projects, like Daidalos or Prime, have invested considerable effort to bring IdM forward, to take advantage of features like improved usability and security. Nevertheless, there are important issues that have not been addressed so far. The SWIFT project leverages IdM as a key technology of the Future Internet, tackling problems like the integration of the network and application layer from an IdM perspective as well as the use of electronic identity cards. Moreover, aspects like the integration of several user devices, backward compatibility and a new access control infrastructure are required by future IdM solutions. We consider all these aspects by extending existing IdM solutions with six new security and privacy enablers that are part of the overall SWIFT framework. These enablers have been partially implemented towards a new IdM architecture. First evaluation results of the implementation are promising to pave the way towards future IdM solutions. Copyright © 2010 The authors.

关键词： Authentication

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