基于双栈和隧道技术构建校园网IPv6实验床

介绍了IETF工作组提出IPv6过渡机制的背景,详细分析和研究了双栈协议、隧道技术和翻译器技术等3种常用的过渡机制,重点论述了双栈、隧道技术以及双栈与隧道协同工作的实现原理,并通过一个IPv6实验床的建设,利用IPv6的过渡机制如双栈协议和隧道技术,提供了校园网用户IPv6接入服务,真正实现了IPv4网络和IPv6网络之间的互联互通,为在校园网全面开展IPv6的组网和研究积累了经验.     

Impact of QoS operations on an experimental testbed network

By making the best use of limited bandwidth, quality of service (QoS) provisioning over internet is essential for satisfying various types of internet-application requirements. The traffic classification and scheduling are the key functions to provide various kinds of class of service (CoS) under an overload condition. This paper investigates QoS performance in a network equipment testbed when implementing these main functions. We examine the major CoS functions provided by the Juniper T320 router, and measure their performance. In addition to fundamental analysis of the QoS behavior, we show the impact of QoS operations on a parallel system distributed in multi-domain networks as a practical case study of grid environments.     

CHIMPNET: a network testbed

CHIMPNET is a testbed system; it is an inexpensive flexible interconnection of microprocessors to support experiments with distributed systems, including studies of distributed database management systems using various interconnection topologies and access protocols. This paper presents system hardware and software features including interface hardware and experiment control mechanisms.     

Optimal adaptation decision-taking for terminal and network quality-of-service

In order to cater to the diversity of terminals and networks, efficient, and flexible adaptation of multimedia content in the delivery path to end consumers is required. To this end, it is necessary to associate the content with metadata that provides the relationship between feasible adaptation choices and various media characteristics obtained as a function of these choices. Furthermore, adaptation is driven by specification of terminal, network, user preference or rights based constraints on media characteristics that are to be satisfied by the adaptation process. Using the metadata and the constraint specification, an adaptation engine can take an appropriate decision for adaptation, efficiently and flexibly. MPEG-21 Part 7 entitled Digital Item Adaptation standardizes among other things the metadata and constraint specifications that act as interfaces to the decision-taking component of an adaptation engine. This paper presents the concepts behind these tools in the standard, shows universal methods based on pattern search to process the information in the tools to make decisions, and presents some adaptation use cases where these tools can be used.     

Building an IP-based community wireless mesh network: Assessment of PACMAN as an IP address autoconfiguration protocol

Wireless mesh networks are experiencing rapid progress and inspiring numerous applications in different scenarios, due to features such as autoconfiguration, self-healing, connectivity coverage extension and support for dynamic topologies. These particular characteristics make wireless mesh networks an appropriate architectural basis for the design of easy-to-deploy community or neighbourhood networks. One of the main challenges in building a community network using mesh networks is the minimisation of user intervention in the IP address configuration of the network nodes. In this paper we first consider the process of building an IP-based mesh network using typical residential routers, exploring the options for the configuration of their wireless interfaces. Then we focus on IP address autoconfiguration, identifying the specific requirements for community mesh networks and analysing the applicability of existing solutions. As a result of that analysis, we select PACMAN, an efficient distributed address autoconfiguration mechanism originally designed for ad-hoc networks, and we perform an experimental study – using off-the-shelf routers and assuming worst-case scenarios – analysing its behaviour as an IP address autoconfiguration mechanism for community wireless mesh networks. The results of the conducted assessment show that PACMAN meets all the identified requirements of the community scenario.     

Building an automated and self‐configurable emulation testbed for grid applications

Distributed systems, such as grids, are composed of geographically distributed computing elements that belong to multiple administrative domains and are controlled by multiple entities. It is unlikely that testers are able to acquire repeatedly the same resources, for the same amount of time, and under the same network conditions, which are paramount requirements for enabling reproducible and controlled tests in software under development. An alternative to experiments in real testbeds is the use of emulation tools, which allow the software to run in an environment that behaves like a distributed system. Although advances in virtualization technology allowed the development of efficient emulators, few efforts were put in making operation of such emulators easier. This paper presents the design and the development of the Automated Emulation Framework that allows automatic mapping of virtual machines to hosts, virtual machine deployment, network configuration, and proactive management and reconfiguration of the virtual infrastructure. Copyright © 2010 John Wiley & Sons, Ltd.     

Com-WSN：一种组件化的无线传感器网络测试平台

随着对无线传感器网络研究的不断深入,人们越来越重视利用真实传感器节点进行网络测试。而在真实测试床上实现和测试新的协议需要大量的编码工作。为了能够降低测试编码的复杂度,提出了基于组件的无线传感器网络测试平台Com-WSN。Com-WSN充分考虑了系统资源的合理分配和协议功能的组件化,保证了平台的易用性和扩展性。通过在MICAz平台上的测试,表明Com-WSN能够有效减少编码工作量,提高测试效率,具有很好的易维护性和可扩展性。     

A testbed for evaluating network construction algorithms from GPS traces

Developing algorithms which construct street/pedestrian networks from crowd-sourced GPS traces has been an ongoing research since the outbreak of inexpensive GPS receivers on mobile devices. Although, the proposed algorithms are evaluated by their developers, the evaluation results cannot be used to compare their accuracy because: (a) different algorithms target different types of networks, some designed for complicated networks while others for simple ones, (b) GPS traces, used in different studies, are not the same, some of them are more accurate and denser than others, and (c) the constructed networks are evaluated either qualitatively or with different quantitative metrics. Lack of a comprehensive testbed for evaluating network construction algorithms has made it difficult for authors, reviewers, and readers to monitor the effectiveness of such algorithms. This study establishes a testbed for evaluating network construction algorithms containing three components: (a) street and pedestrian networks with different densities and complexities as the baseline, (b) collections of GPS traces with different accuracies and sampling rates to be used by algorithms to construct those networks, and (c) three quantitative metrics to indicate the completeness, precision, and topology correctness of the constructed network, in addition to the algorithm's time complexity, conventionally used to indicate its time performance. This testbed not only paves the way for comparing network construction algorithms but also allows researchers to focus on their algorithms rather than collecting data for testing it or looking for ways to describe its accuracy.     

A queueing network model for a distributed database testbed system

A queuing network model for analyzing the performance of a distributed database testbed system with a transaction workload is developed. The model includes the effects of the concurrency control protocol (two-phase locking with distributed deadlock detection), the transaction recovery protocol (write-ahead logging of before-images), and the commit protocol (centralized two-phase commit) used in the testbed system. The queuing model differs from previous analytical models in three major aspects. First, it is a model for a distributed transaction processing system. Second, it is more general and integrated than previous analytical models. Finally, it reflects a functioning distributed database testbed system and is validated against performance measurements     

移动网络的未来:无线IP网络

本论文论述了移动通信技术的发展历程．提出了无线IP网络的概念，并对无线IP网络中的主要技术进行讨论．提出并分析了无线IP网络发展中存在的问题．     

Wireless network extension using mobile IP

Over the last two decades, we have seen a dramatic shift in computing systems, away from the monolithic mainframe and toward increasingly distributed, client-server systems. One of the key elements enabling the success of the distributed computing environment was the interconnecting network technology. High-speed, reliable network hardware and protocols evolved to support client-server applications. Network technology has now progressed to the point that applications are being written to specifically exploit the capabilities of the network. The explosion of World Wide Web applications is the latest example of the fact that the network is now the focus of the distributed computing environment. In a concurrent development, personal computing platforms placed increasingly powerful systems in ever smaller form factors. Users have embraced these advances: Mobile computers, in the form of laptops, palmtops, and personal digital assistants (PDAs), are a significant element of the current computing environment. However, to be fully productive, the mobile computer user requires access to the network. Further, access to a network is not sufficient. Mobile users need access to the same network-the same resources and services and communications capabilities-that they would if they were at their desktops. We refer to this concept of providing home network access to the mobile user as network extension. Addressing many requirements for practical wireless access, this Internet technology aids the development of advanced data services for wireless networks, including the integrated dispatch enhanced network     

ACL在IP网络中的应用

ACL即访问控制列表,是用来过滤与控制进出路由器或交换机数据流的一种访问控制技术,目前在IP网络中有着越来越多的应用。该文就ACL的产生背景、在IP网络中的应用,以及在部分厂商设备中的实现原理,作了较为详细的介绍。     

A quality-of-service specification for multimedia presentations

The bandwidth limitations of multimedia systems force trade-offs between presentation-data fidelity and real-time performance. For example, digital video is commonly encoded with lossy compression to reduce bandwidth, and frames may be skipped during playback to maintain synchronization. These trade-offs depend on device performance and physical data representations that are hidden by a database system. If a multimedia database is to support digital video and other continuous media data types, we argue that the database should provide a quality-of-service (QOS) interface to allow application control of presentation timing and information-loss trade-offs. This paper proposes a data model for continuous media that preserves device and physical data independence. We show how to define formal QOS constraints from a specification of ideal presentation outputs. Our definition enables meaningful requests for endto-end service guarantees, while leaving the database system free to optimize resource management. We propose one set of QOS parameters that constitute a complete model for presentation error, and we show how this error model extends the opportunities for resource optimization.     

电信IP承载网安全防御

IP承载网的安全防御是保障电信运营商网络安全的关键,也是信息安全领域的一个热门课题。本文首先分析了IP承载网面临的安全风险,然后介绍了完善的安全体系架构,并提出了一个基于安全域、有针对性地部署安全防御策略的解决方案。     

Active network supports for mobile IP

The basic mobile IP protocol is difficult to implement on the traditional IP network and not flexible and efficient under certain conditions.For example,firewalls or boundary routers may drop packets sent by mobile nodes for security reasons.Traditional networking devices such as routers cannot dynamically load and unload extended services to achieve different qualities of services.In this paper,a new scheme of using the active network to support the mobile IP is presented.The Softnet,a prototype of active networks based on mobile agents,is introduced.The active network is characterized by the programmability of its intermediate nodes and therefore presents dynaic and flexible behaviors.Special services can be dynamically deployed onto the active nodes in the Softnet.This property is definitely required in implementing the mobile IP protocols.The SOftnet.This property is definitely required in implementing the mobile IP protocols.The Softnet.This property is definitely required in implementing the mobile IP protocols.The Softnet supports not only the basic mobile IP protocol but also other extended mobile IP protocols.Virtual networks for mobile IP services are dynamically formed by mobile agents in the Softnet to provide different qualities of services.     

基于IP网络的多媒体视频处理

本文对视频处理和H.323协议[1]体系结构作了简要分析,在此基础上对本文的核心部分—系统开发进行了详细的阐述,并分析了视频处理的上层调用。     

Cellular universal IP for nested network mobility

In recent years, network mobility (NEMO) has been studied extensively due to its potential applications in military and public transportation. NEMO basic support protocol (NBSP), the current de facto NEMO standard based on mobile IPv6, can be readily deployed using the existing mobile IPv6 infrastructure. However, NBSP’s root in mobile IPv6, such as the need of care-of address (CoA) and tunneling, results in substantial performance overhead, generally known as route sub-optimality, in nested NEMO environments. This paper tackles this problem by proposing a scheme based on cellular universal IP (CUIP) to eliminate the need for CoA and tunneling in supporting nested network mobility. Using quantitative analysis, we show that the proposed scheme outperforms the existing nested NEMO schemes by multiple folds in terms of bandwidth overhead. We also show how IP fragmentation negatively impacts route optimality, and that the proposed scheme is inherently superior to the existing schemes in this regard. More importantly, while the scalability of the existing schemes generally deteriorates with the network size, the complexity of our proposed scheme is independent of the network size and thus is far more scalable. Our results show that the proposed scheme is particularly suitable for nested NEMO networks formed by mobile routers with random and ad hoc movement patterns.     

EPON中一种基于QoS的MAC协议设计

提出了一种新的EOPN利用动态带宽分配算法来保证服务质量的MAC协议。该协议使得高优先级数据的延时和抖动减小;当网络对新接入的ONU进行初始化时对高优先级数据没有影响;同时,通过OLT控制中优先级数据的接入量保证其带宽分配的公正性。确保网络的QoS。