A behavioral type system and its application in Ptolemy II

Interface automata [deH01] have been introduced as an interface theory [deH01a] capable of functioning as a behavioral type system. Behavioral type systems describe dynamic properties of components and their compositions. Like traditional (data) type systems, behavioral type systems can be used to check compatibility of components. In this paper, we use interface automata to devise a behavioral type system for Ptolemy II, leveraging the contravariant and optimistic properties of interface automata to achieve behavioral subtyping and polymorphism. Ptolemy II is a software framework supporting concurrent component composition according to diverse models of computation. In this paper, we focus on representing the communication protocols used in component communication within the behavioral type system. In building this type system, we identify two key limitations in interface automata formalisms; we overcome these limitations with two extensions, transient states and projection automata. In addition to static type checking, we also propose to extend the use of interface automata to the on-line reflection of component states and to run-time type checking, which enable dynamic component creation, morphing application structure, and admission control. We discuss the trade-offs in the design of behavioral type systems.Received September 2002Accepted in revised form November 2003 by M. Broy, G. Lüttgen and M. Mendler     

Team Automata for Security: – A Survey –

In [Kleijn, J., Team Automata for CSCW – A Survey –, Petri Net Technology for Communication-Based Systems—Advances in Petri Nets, LNCS 2472, Springer, 2003, 295–320], Kleijn presented a survey of the use of team automata for the specification and analysis of phenomena from the field of computer supported cooperative work, in particular notions related to groupware systems. In this paper we present a survey of the use of team automata for the specification and analysis of some issues from the field of security. In particular, we show how team automata can adequately be used to model and verify various access control policies, multicast/broadcast communication protocols, and general (cryptographic) communication protocols.     

Efficient Multiple Multicast on Heterogeneous Network of Workstations

In recent years, network of workstations/PCs (so called NOW) are becoming appealing vehicles for cost-effective parallel computing. Due to the commodity nature of workstations and networking equipment, LAN environments are gradually becoming heterogeneous. The diverse sources of heterogeneity in NOW systems pose a challenge on the design of efficient communication algorithms for this class of systems. In this paper, we propose efficient algorithms for multiple multicast on heterogeneous NOW systems, focusing on heterogeneity in processing speeds of workstations/PCs. Multiple multicast is an important operation in many scientific and industrial applications. Multicast on heterogeneous systems has not been investigated until recently. Our work distinguishes itself from others in two aspects: (1) In contrast to the blocking communication model used in prior works, we model communication in a heterogeneous cluster more accurately by a non-blocking communication model, and design multicast algorithms that can fully take advantage of non-blocking communication. (2) While prior works focus on single multicast problem, we propose efficient algorithms for general, multiple multicast (in which single multicast is a special case) on heterogeneous NOW systems. To our knowledge, our work is the earliest effort that addresses multiple multicast for heterogeneous NOW systems. These algorithms are evaluated using a network simulator for heterogeneous NOW systems. Our experimental results on a system of up to 64 nodes show that some of the algorithms outperform others in many cases. The best algorithm achieves completion time that is within 2.5 times of the lower bound.     

综合导航信息模拟系统的设计与实现

针对综合导航显控台的维修检测时的信息模拟需求,介绍了一种基于PC/104的综合导航信息模拟系统的设计;该系统基于模块化设计思想,提供4路RS422串行通信接口(19200bps)、2路CAN总线通信接口(500kbps)和IP组播网络接口,采用事件驱动和多线程编程技术,提供三种通信方式数据流传输实现综导显控台外围环境模拟;该系统可以模拟GPS、罗兰C、平台罗经等十四种设备信息模拟,并实现数据记录、参数存储和故障模拟等功能;最终将信息模拟系统与某型显控台联调,系统运行良好,通信实时性很高,实现各部分功能,并具有很好的扩展性。     

Nonblocking k-fold multicast networks

Multicast communication involves transmitting information from a single source to multiple destinations and is a requirement in high-performance networks. Current trends in networking applications indicate an increasing demand in future networks for multicast capability. Many multicast applications require not only multicast capability, but also predictable communication performance such as guaranteed multicast latency and bandwidth. In this paper, we present a design for a nonblocking k-fold multicast network, in which any destination node can be involved in up to k simultaneous multicast connections in a nonblocking manner. We also develop an efficient routing algorithm for the network. As can be seen, a k-fold multicast network has significantly lower network cost than that of k copies of ordinary 1-fold multicast networks and is a cost effective choice for supporting arbitrary multicast communication.     

Communication Models for a Free-Space Optical Cross-Connect Switch

We design and analyze communication algorithms for an optical switch based on the electroholographic effect, that provides capabilities for configuration changes and a limited multicast. As configuration changes incur a high overhead, we suggest the use of a high-speed forwarding unit as part of the network interface. We develop broadcast algorithms that trade off the number of configuration changes and forwarding operations in order to achieve the minimal completion time. For general point- to-point communication, we use the limited multicast to create a spanning topology along which messages can be forwarded. This requires care to avoid collisions, but is still preferable to using configuration changes if the topology is rich enough but still has a low degree.     

Topology Design of Network-Coding-Based Multicast Networks

It is anticipated that a large amount of multicast traffic needs to be supported in future communication networks. The network coding technique proposed recently is promising for establishing multicast connections with a significantly lower bandwidth requirement than that of traditional Steiner-tree-based multicast connections. How to design multicast network topologies with the consideration of efficiently supporting multicast by the network coding technique becomes an important issue now. It is notable, however, that the conventional algorithms for network topology design are mainly unicast-oriented, and they cannot be adopted directly for the efficient topology design of network-coding-based multicast networks by simply treating each multicast as multiple unicasts. In this paper, we consider for the first time the novel topology design problem of network-coding-based multicast networks. Based on the characteristics of multicast and network coding, we first formulate this problem as a mixed-integer nonlinear programming problem, which is NP-hard, and then propose two heuristic algorithms for it. The effectiveness of our heuristics is verified through simulation and comparison with the exhaustive search method. We demonstrate in this paper that, in the topology design of multicast networks, adopting the network coding technique to support multicast transmissions can significantly reduce the overall topology cost as compared to conventional unicast-oriented design and the Steiner-tree-based design.     

基于场景规约的构件式系统设计分析与验证

使用接口自动机及接口自动机网络来描述构件式系统的行为设计模型,使用UML顺序图表示基于场景的需求规约,对系统设计阶段的构件交互行为的动态兼容性进行形式化分析和检验.通过对接口自动机网络状态空间的分析,给出了一系列算法以检验系统行为的存在一致性以及几种不同形式的强制一致性性质,包括前向强制一致性、逆向强制一致性以及双向强制一致性等.     

一种支持NC++语言的多目通信机制(NCMCAST)

分布式处理要求分布式系统提供可靠高效的通信手段,本文在分析了分布式系统对多目通信机制要求的基础上,设计并实现了一个支持面向对象的分布式程序设计语言ＮＣ＋＋的多目通信机制ＮＣＭＣＡＳＴ。实验证明ＮＣＭＣＡＳＴ向ＮＣ＋＋提供了可靠,保序的多目通信机制。     

支持高效组传送的操作系统

很多因特网服务的普遍需要是在相同的时间内准确地发送相同的数据到很多的主机.没有IP层的多点传送,组通信的形式将会通过传送数据至每个希望的主机来实现.虽然该方法是简便的,但是它对于发送主机来说是效率极低的.本文引入了一个基于内核的技术,只是使用了最少的附加物至发送操作系统接口,实现高效地促进组通信传送发送操作,文中还说明了该方法的设计和原型实现.     

高效的动态安全组播密钥协商方案

组播提供了一种发送者可以同时发送信息到多个接收者的高效通信机制。设计高效的密钥协商方案是实现安全组播的主要环节。以双线性对为工具,本文提出了一个新的基于身份的动态安全组播密钥协商方案,并具体地分析了当新提出的密钥协商方案用于组播时,子组之间的通信过程,以及组成员动态变化时密钥的更新过程,结果表明该方案在降低计算和通信代价方面取得了较好的效果,且满足组播密钥协商的各种安全要求。     

Hierarchical agent-based secure and reliable multicast in wireless mesh networks

We propose and analyze a hierarchical agent-based secure and reliable multicast (HASRM) algorithm for efficiently supporting secure and reliable mobile multicast in wireless mesh networks, with design considerations given to minimize the overall network cost incurred by reliable multicast packet delivery, mobility management, security key management, and group membership maintenance. HASRM dynamically maintains a group of multicast agents running on mesh routers for integrated mobility and multicast service management and leverages a hierarchical multicast structure for secure and reliable multicast data delivery. The regional service size of each multicast agent is a key design parameter. We show via model-based performance analysis and simulation validation that there exists an optimal regional service size that minimizes the overall communication cost and the optimal regional service size can be dynamically determined. We demonstrate that HASRM under optimal settings significantly outperforms traditional algorithms based on shortest-path multicast trees extended with user mobility, security, and reliability support. We also show that a variant of HASRM is superior to a recently proposed multicast algorithm for secure group communication in wireless mesh networks.     

基于PIM-SM的域内组播设计

PIM-SM是一个不依赖于某一特定单播路由协议的组播路由协议,为组播数据转发提供路由信息。介绍了IP组播原理,分析了组播通信的优点,概述了组播路由协议。研究了基于PIM-SM的组播网络设计与实现方法,并给出了相关的网络配置方案。     

GLBM: A new QoS aware multicast scheme for wireless mesh networks

Wireless mesh networks (WMNs) have been attracting significant attention due to their promising technology. The WMN technology is becoming a major avenue for the fourth generation of wireless mobility. Communication in large-scale wireless networks can create bottlenecks for scalable implementations of computationally intensive applications. A class of crucially important communication patterns that have already received considerable attention in this regard are group communication operations, since these inevitably place a high demand on network bandwidth and have a consequent impact on algorithm execution times. Multicast communication has been among the most primitive group capabilities of any message passing in networks. It is central to many important distributed applications in science and engineering and fundamental to the implementation of higher-level communication operations such as gossip, gather, and barrier synchronisation. Existing solutions offered for providing multicast communications in WMN have severe restriction in terms of almost all performance characteristics. Consequently, there is a need for the design and analysis of new efficient multicast communication schemes for this promising network technology. Hence, the aim of this study is to tackle the challenges posed by the continuously growing need for delivering efficient multicast communication over WMN. In particular, this study presents a new load balancing aware multicast algorithm with the aim of enhancing the QoS in the multicast communication over WMNs. Our simulations experiments show that our proposed multicast algorithm exhibits superior performance in terms of delay, jitter and throughput, compared to the most well known multicast algorithms.     

接口自动机--一种用于组件组合的形式系统

接口自动机是描述基于组件系统中组件及组件间交互行为的形式化工具。接口自动机在处理组件组合问题时所使用的“乐观方法”和博弈思想是区别于其它形式化工具的关键点。本文对接口自动机、时间接口自动机和资源接口及其中的博弈思想进行综述。在同其它形式化方法比较的基础上,指出了接口自动机的长处和局限。文中总结了接口自动机在理论上和实际中的意义并对其应用前景做了展望。     

Path-Based Multicast Communication in Wormhole-Routed Unidirectional Torus Networks

This paper addresses the problem of one-to-many, or multicast, communication in wormhole-routed,n-dimensional torus networks. The proposed methods are designed for systems that support intermediate reception, which permits multidestination messages to be pipelined through several nodes, depositing a copy at each node. A key issue in the design of such systems is the routing function, which must support both unicast and multicast traffic while preventing deadlock among messages. An efficient, deadlock-free routing function is developed and used as a basis for a family of multicast algorithms. TheS-torusmulticast algorithm uses a single multidestination message to perform an arbitrary multicast operation. TheM-torusalgorithm is a generalized multiphase multicast algorithm, in which a combination of multidestination messages is used to perform a multicast in one or more communication steps. Two specific instances of the M-torus algorithm, theM_d-torusandM_u-torusmulticast algorithms, are presented. These algorithms produce contention-free multicast operations and are deadlock-free under all combinations of network traffic. A simulation study compares the performance of the different multicast algorithms, and implementation issues are discussed. The results of this research are applicable to the design of architectures for both wormhole-routed massively parallel computers and high-speed local area networks with wormhole-routed switch fabrics.     

基于MANET的QoS多播路由协议研究

在自组织网络上运行多媒体应用，正在成为随遇计算和随遇通信环境中的一个完整部分，同时提出了对QoS和多播的需求，如何设计有效的QoS多播路由协议已经成为当前研究的热点问题。本文介绍了自组网QoS多播路由协议研究方面的一些最新进展，并对该研究所提出的路由算法进行了比较和分析，有助于进一步改进和完善自组网的QoS多播路由技术。     

改进的轻型CORBA事件服务的实现

CORBA事件服务提供了ORB之间异步、多目的通信方式.但标准的事件服务规范过于繁杂,服务质量也有待改进.根据项目应用需求,对事件规范进行了扩充,引入了对事件信道进行管理的模块,同时对标准事件服务规范中的类型事件特征进行删减.然后,基于国内惟一的开源CORBA实现--Orbas,通过代理的设计模式,实现了一个轻型的事件服务,并且在接口级和应用程序级实现对QoS的提高.结果表明,该事件服务可以作为项目的消息传递中间件的底层通信模块,完成分布式对象之间的异步、多目通信.     

On Bandwidth-Efficient Overlay Multicast

In this paper, we propose a new multicast delivery mechanism for bandwidth-demanding applications in IP networks. Our mechanism, referred to as multiple-destination overlay multicast (MOM), combines the advantages of IP multicast and overlay multicast. We formulate the MOM routing problem as an optimization problem. We then design an algorithm based on Lagrangian relaxation on our formulation and propose a distributed protocol based on the algorithm. For network operators, MOM consumes less network bandwidth than both IP multicast and overlay multicast. For users, MOM uses less interface bandwidth than overlay multicast.     

AODV路由算法的多播通信

ah—hoc网络具有网络拓扑结构易变的特性，苒加上移动网络本身具有的通信带宽有限，电池能源有限等特性。使得设计适合ad-hoc的路由协议具有一定的难度。AODV（Ad Hoc On—demand Distance Vector）是现在被广泛应用于adhoc网络中的一种按需路由算法，并且还设计了多播功能。多播是指一次给一个有明确定义的组发送消息。AODV的多播功能是路由器通过建立多播书树的方法实现的。本文主要介绍AODV路由协议算法的多播通信，其中详细介绍了多播树的建立过程和维护过程。并且选取传输半径和发包率为参