应用层多播中基于角色和任务的工作流访问控制模型

该文针对目前Internet安全组通信技术的现状,通过分析目前已有的应用层多播机制的特点,提出了应用层多播中的基于角色和任务的工作流访问控制模型。在应用层多播工作流的具体环境中构造了一个ALM-T-RBAC系统,以实现应用层多播通信系统的安全访问控制。     

一种基于遗传算法的半动态应用层多播协议

将半动态应用层多播通信分解为静态起始和动态维护两种阶段交替出现的过程．在起始阶段．采用基于遗传算法的多播路由机制构建优化的静态多播树；在维护阶段，采用拓扑维护机制、路由性能监控机制和路由更新机制．对多播拓扑的动态进行快速响应．仿真结果表明．该协议同时具备优化多播树性能和快速维护多播拓扑的能力，改善了通信过程中多播树的整体性能．     

基于自适应层次化聚类算法的应用层多播协议

自适应层次化聚类算法将单层拓扑映射为一个层次化结构，改善了应用层多播算法的可扩展性。但它也引入了较高的根节点度数，无法有效控制多播树的形态，不适合用于多媒体等内容的多播通信。通过“剪枝重置”和“构建顶层拓扑”操作，可以弥补自适应层次化聚类算法的缺陷。仿真试验表明，前者可以减少树的层数和同一个聚类中的节点密度；后者可以减轻多播树根节点的负担。相对于采用传统路由算法得到的单层拓扑多播树，该文得到的多播树在开销、时延和度数方面都有显著的优化。     

一种时延受限的多播路由算法

很多实时多媒体应用要求通信网络提供多播服务支持，而且往往需要传输的信息满足源端到目的端的时延约束。该文对时延约束的多播路由问题进行了研究，基于原有的从源端到目的端的时延受限路径构造算法，提出了一种时延受限多播路由算法。该算法能够快速构建满足时延约束的多播树。理论分析表明，该算法的时间复杂度和CDKS算法相同。仿真实验结果表明，该算法所构建的多播树代价低于CDKS算法。     

基于最大干扰网络编码的应用层多播算法

构建于终端系统的应用层多播具有网络层多播不可比拟的优势,为了提高应用层多播的效率和性能,提出一种基于最大干扰网络编码的应用层多播算法。该算法在采用网络编码的基础上,在多播路径选择上通过考虑源到多个目的节点路径间的最大干扰,来提高编码的利用效率,有效节省带宽。仿真表明,相比较一般应用层多播算法和基于网络编码的多播算法,本算法在提高网络吞吐量和资源利用率方面都有更好的表现。     

基于LKH的多播密钥管理改进方案

在LKH的基础上结合共享函数技术,提出了一个多播密钥管理的改进方案,该方案有效地减少了组控制器端的密钥存储量,密钥更新的延时和通信开销,从而提高了多播密钥管理的性能。     

采用定位优先方法的应用层组播的设计

在应用层组播设计中，如果分发树的构造过程忽略了底层的网络拓扑结构和链路特征，则多播性能将会很差。该文采用一种定位算法，在不引入过多开销的情况下，将靠近的节点集中在一起。在此基础上，可建立一个拓扑敏感的分层应用层多播体系结构。     

基于平衡树的应用层多播树构建算法

应用层多播协议通过生成树向其组成员发送数据包,一个节点失效则会引起生成树的分裂,并导致下游成员节点无法接收数据包,这正体现了应用层多播系统的脆弱性。为提高应用层多播的健壮性,提出一种基于K叉平衡树结构的应用层多播树构建的改进方案。     

一种基于树环结构的应用层多播协议

应用层多播是互联网研究的一个重要课题.现有的应用层多播协议主要解决可扩缩性问题,针对网络系统最为关键的可靠性问题的研究还很少.本文提出了一种改进应用层多播生存性和可扩缩性的树型环结构及该结构的构建算法;提出了一种新的树环结合的应用层多播协议,该协议综合了树型结构和环型结构的优点,具有可靠性高、扩展性好、数据传输效率高等优点.仿真结果表明,该协议能较好地适用于大规模应用层多播环境.     

基于遗传算法的应用层多播路由方案

通过分析应用层多播树的路由约束,定义了3个适值函数,分别考察应用层多播树在开销、平衡和网络层业务量均衡3方面的性能。并根据生成的总适值函数进行遗传算法操作．仿真结果表明,与基于几何规则的应用层路由算法比较,本文提出的算法对多播树的3方面性能都有所优化,树的平衡和网络层业务量均衡性能的优化程度尤为明显．     

OverSim:可扩展的应用层组播网络仿真框架

应用层组播作为IP组播的一个可行替代方案日益成为Internet应用研究的一个热点。如何仿真大规模、动态的应用层组播覆盖网络已经成为应用层组播方案研究人员面临的一个共同问题。本文在分析当前几款主流的覆盖网络仿真软件的基础上,提出了采用基于OMNet++网络仿真环境的Over-Sim覆盖网络仿真框架来模拟大规模、动态的应用层组播覆盖网络,并在此基础上研究分析可扩展的应用层组播方案。最后我们采用OverSim实现了对应用层组播协议Scribe的仿真并对结果进行了分析。仿真结果表明,OverSim可以在有限的硬件环境下,稳定地仿真高达上万个节点的大规模动态覆盖网络,仿真过程中内存消耗较低,且与覆盖网络规模呈线性关系。     

An overlay multicast protocol for live streaming and delay-guaranteed interactive media

In many collaborative multimedia applications, there is often a requirement for simultaneously supporting live streaming and shareable interaction. A major challenge in designing such an application by overlay multicast is how to simultaneously provide scalable live streaming and delay-guaranteed interactive media. Live streaming by overlay multicast incurs additional application-layer latency, which conflicts with the delay-sensitive property of interactive media. To handle this dilemma, in this paper, we propose a layered degree-constrained overlay multicast protocol, which organizes the overlay multicast tree as a layered degree-constrained core tree and an extended tree. The core tree maintains available resources in its top layers for subsequent two-way interaction, whereas the extended tree expands the core tree for one-way live streaming. Our simulation and experimental results show that the proposed overlay multicast protocol can simultaneously provide delay-guaranteed interactive media as well as scalable live streaming.     

Multicast tree rearrangement to recover node failures in overlay multicast networks

Overlay multicast makes use of the Internet as a low level infrastructure to provide multicast service to end hosts. The strategy of overlay multicast slides over most of the basic deployment issues associated with IP multicast, such as end-to-end reliability, flow and congestion control, and assignment of an unique address for each multicasting group.     

A Scalable Overlay Multicast Architecture for Large-Scale Applications

In this paper, we propose a two-tier overlay multicast architecture (TOMA) to provide scalable and efficient multicast support for various group communication applications. In TOMA, multicast service overlay network (MSON) is advocated as the backbone service domain, while end users in access domains form a number of small clusters, in which an application-layer multicast protocol is used for the communication between the clustered end users. TOMA is able to provide efficient resource utilization with less control overhead, especially for large-scale applications. It also alleviates the state scalability problem and simplifies multicast tree construction and maintenance when there are large numbers of groups in the network. To help MSON providers efficiently plan backbone service overlay, we suggest several provisioning algorithms to locate proxies, select overlay links, and allocate link bandwidth. Extensive simulation studies demonstrate the promising performance of TOMA     

基于斐波那契序列的应用层组播协议

提出一种基于tree覆盖网络拓扑的可扩展高效应用层组播协议-HFTM ( Hierarchical Fibonacci Tree Multicast ).HFTM通过分层和分群的思想将所有组播组成员构造成一个特殊的层次化结构,在进行群划分时,充分考虑了底层网络拓扑特征,尽量避免数据包在代价昂贵的链路上进行传输,从而减少组播延迟.另外,采用一种新颖的基于斐波那契序列的组播算法将群内成员构造成一棵高效的斐波那契组播树,利用此树进行群内组播.实验结果表明底层网络拓扑特点的考虑以及斐波那契组播树的构造使HFTM协议获得更好的组播延迟性能.     

GMAC: An overlay multicast network for mobile agent platforms

The lack of proper support for multicast services in the Internet has hindered the widespread use of applications that rely on group communication services such as mobile software agents. Although they do not require high bandwidth or heavy traffic, these types of applications need to cooperate in a scalable, fair and decentralized way. This paper presents GMAC, an overlay network that implements all multicast related functionality–including membership management and packet forwarding–in the end systems. GMAC introduces a new approach for providing multicast services for mobile agent platforms in a decentralized way, where group members cooperate in a fair way, minimize the protocol overhead, thus achieving great scalability. Simulations comparing GMAC with other approaches, in aspects such as end-to-end group propagation delay, group latency, group bandwidth, protocol overhead, resource utilization and failure recovery, show that GMAC is a scalable and robust solution to provide multicast services in a decentralized way to mobile software agent platforms with requirements similar to MoviLog.     

一种动态负载均衡的P2P应用层组播方案

基于结构化的P2P基础设施,给出一种动态负载均衡的应用层组播方案--DLBMS.利用Tapestry协议的路由和定位机制,设计了延迟优化的组播转发树结构,采用根节点复制的方法生成多棵不相交的组播转发树,根据负载的变化动态调节组播转发树数目以实现负载均衡和降低源到组成员节点的端到端延迟.通过模拟实验说明了此方案在平均控制负载和端到端平均延迟方面的有效性.     

覆盖多播路由的算法及协议研究综述

虽然IP多播的性能优势无可否认,但是它却面临着部署上的困难。近年来,覆盖多播作为提供多播服务的另一可行途径正不断为人们所认可。本文对覆盖多播路由的算法和协议进行了综述研究,提出了通用的覆盖多播网络模型,对覆盖多播中的路由优化问题进行了分类。在此基础上,介绍了当前重要的覆盖多播路由算法和协议,并对它们的性能参数、所解决的路由问题、系统结构和控制方式等技术特点进行了全面的分析和讨论。另外,本文还指出了覆盖多播路由中一些有待进一步研究的问题。     

Scattercast: an adaptable broadcast distribution framework

Internet broadcasting - the simultaneous distribution of live content streams to a large audience - has a number of interesting applications ranging from real-time broadcasts of audio/video streams for online concerts or sporting events to efficient and reliable large-scale software distribution. We identify three fundamental requirements for scalable broadcasting services: an efficient infrastructure for large-scale broadcasting, an ability to adapt the infrastructure to suit the requirements of a wide range of applications, and ease of deployment of the infrastructure. Although solutions such as the network-layer IP multicast approach and a slew of overlay distribution networks exist today, none of these technologies satisfactorily addresses all of the above concerns. In this paper, we argue that an application-customizable hybrid overlay is well suited to meet these challenges. To this end, we propose an architecture called scattercast that relies on a network of strategically located agents called ScatterCast proXies or SCXs. These agents collaboratively provide the broadcast service for a session. Clients locate a nearby SCX and tap into the session via that SCX. Scattercast constructs a hybrid overlay network composed of unicast links between SCXs that interconnect locally scoped multicast regions. Rather than define a single standardized service model for transmitting data on top of the overlay, scattercast builds a customizable transport framework that provides adaptability by leveraging application-defined semantics to drive the distribution of content. We demonstrate the ability of our architecture to provide efficient distribution via a set of simulation experiments. Finally, we present our experience with the adaptability of the framework by describing two applications, a real-time Internet radio and an online slide-presentation tool, both of which we have built on top of a prototype implementation of the architecture.Received: 15 March 2002, Accepted: 2 October 2002,     

Multicast address management and connection control based on hierarchical autonomous structure

Multicast capability,including multicast address and multicast routing mechanisms,at the network layer is necessary in order to reduce the bandwidth requirements of multiparty,multicast applications.Based on hierarchical autonomous structure in accordance with the self-organization topologies of Internet,the paper puts forward a multicast address management scheme that is shown to be robust and scalable.Connection control hierarchy(CCH) based on master/slave relationship and a simple efficient building algorithm of multi-point connection is also built.The paper also describes the normal operations of multicast address management and multi-point connection controller.Through simulation experiment,HAM CM and DDM of Multicast Address Allocation are compared.HAM integrates the merits of CM and DDM,which is efficient as a whole,robust and scalable.CCH raises the efficiency of connection control,and is highly robust,flexible and scalable.