Fast reroute from single link and single node failures for IP multicast

The rise in multicast implementations has seen with it an increased support for fast failure recovery from link and node failures. Most recovery mechanisms augment additional services to existing protocols causing excessive overhead, and these modifications are predominantly protocol-specific. In this paper, we develop a multicast failure recovery mechanism that constructs protocol independent fast reroute paths to recover from single link and single node failures. We observe that single link failure recovery in multicast networks is similar to recovering unicast traffic, and we use existing unicast recovery mechanisms for multicast traffic. We construct multicast protection trees that provide instantaneous failure recovery from single node failures. For a given node x, the multicast protection tree spans all its neighbors and does not include itself. Thus, when the node fails, the neighbors of the node are connected through the multicast protection tree instead of node x, and forward the traffic over the multicast protection tree for the duration of failure recovery. The multicast protection trees are constructed a priori, without the knowledge of the multicast traffic in the network. Based on simulations on three realistic network topologies, we observe that the multicast protection trees increase the routing table size only by 38% on average and the path length between any source–destination pair by 13% on average.     

应用层组播研究进展

组播技术是一种针对多点传输和多方协作应用的组通信模型,有高效的数据传输效率,是下一代Internet应用的重要支撑技术。早期的组播技术研究试图在IP层提供组播通信功能,但IP组播的实施涉及到对现有网络基础设施的调整,因此,大规模应用受到限制。近两年来,随着Peer-to-Peer(P2P)研究的兴起,基于应用层的组播技术也逐渐受到广泛关注。应用层组播协议将组成员节点自组织成覆盖网络,在主机节点实现组播功能,为数据多点并发传输提供服务。将组播功能从路由器迁移到主机上能有效解决许多与IP组播有关的问题,但同时也带来了一些新的挑战。本文分析了目前应用层组播研究的主要内容及技术特点,描述了协议设计所涉及的关键技术及面临的主要挑战,总结了现有工作及相关进展。     

基于主机的跨网段多播系统设计

多播是一种重要的群组通信技术,在许多领域正得到越来越广泛的应用.传统的多播服务由于实现在TCP/IP协议的网络层,跨网段的多播需要路由器的支持.给出了一种基于主机端应用程序的跨网段多播解决方案,在不改变现有网络结构的基础上,为处于不同子网的主机提供了群组通信服务.详细阐述了该解决方案的设计思想以及适用情况.     

IP multicast routing through ATM networks

The purpose of this paper is to have a closer look at the ‘core’ technology providing interworking between connectionless TCP/IP internetworks and switched ATM networks. The scope of the paper is IP multicast, while the main focus is on the network side of multicast, more precisely, on layers three and two of Internet architecture dealing with IP multicast routing. The paper analyses both practically available solutions and those being currently under discussion in IETF as Internet drafts. As a background of this comparison, the possible convergence of IP and ATM multicast service models is discussed. Major conclusions, based on simulation studies and scalability analysis are: (i) the high mapping overhead requires a separate address resolution service for unicast and multicast addresses; and (ii) efficient convergence has to make obsolete classical IP over ATM (M. Laubach, Classical IP and ARP over ATM, Network Working Group, Request for Comments: 1577, Category: Standards Track, January, 1994 [1]) in order to permit ‘cut-through’ within the ATM domain.     

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.     

Reliable overlay multicast trees for private Internet broadcasting with multiple sessions

With rapid advances of computing technologies and high speed networks, various high volume multimedia services have become popular in the Internet. Private Internet broadcasting is a typical way to support these services and overlay multicast technology is known to be a promising solution to support this method. In an overlay multicast network, members are dynamically joining or leaving their multicast group. To reduce frequent updates of multicast members and provide a reliable multicast route, overlay multicast trees are investigated. The problem is formulated as a binary integer programming which maximizes the minimum link reliability for all multicast sessions. Tabu search heuristic is developed with repeated intensification and diversification. Robust computational result is obtained that is comparable to the optimal solution and applicable in real time.     

基于树与环应用层组播覆盖网的研究与比较

由于应用层组播在部署和实现方面的优势受到学术界的广泛关注.应用层组播协议在不同的覆盖网络拓扑结构(如树、网、环)下具有不同的性能特征.因此,比较应用层组播覆盖网的性能是评估覆盖网络拓扑优缺点的关键.在NS-2下对基于树、环的覆盖网络进行仿真.仿真结果表明,尽管环型覆盖网比树型覆盖网具有较高路径伸展度和较高链路强度,但在单个组播组成员失效或离开的情况下,它提供了恒定的、更低的节点度和较高数据传送率.     

应用层组播树分裂恢复算法研究

应用层组播树是由终端用户构造而成,其稳定性不能得到保证。由于终端用户失效导致组播树分裂,产生多个分支,因此需要快速恢复组播树,保证各组用户接收到组播数据。分析组播树分裂恢复特点,构造了带有时延和度约束的组播树分裂恢复问题数学模型。利用拉格朗日松弛方法分解此复杂问题,提出一种新的应用层组播树分裂恢复算法。仿真实验表明,此算法具有较快的收敛速度,而且算法稳定。     

基于覆盖组播的应用层组通信服务系统

网络层组播是提供一对多或者多对多通信的最佳方式,但是由于其在技术上和非技术上的原因难以在Inteme上部署。设计和实现了一种基于覆盖组播的组通信服务系统,为组通信应用提供组播服务。这个系统独立于路由器的组播机制,能够快速实现与应用系统的集成,而且能够利用多种传输协议,为构建基于Internet的组通信应用系统提供了有效的支持。     

Strategic behavior modeling of multi-service overlay multicast networks based on auction mechanism design

Since the users of overlay multicast networks belong to different administrative domains, they are selfish in nature; resulting in degradation of performance. That is why strategic behavior modeling is a hot topic in the area of the overlay multicast networks. Mechanism design is the most versatile tool for strategic behavior modeling in microeconomics. In this paper, we model the strategic behavior of the selfish peers by leveraging the rich theory of mechanism design using the concept of economic auctions. By considering the bandwidth of services as the commodity, we design a revenue-maximizing auction mechanism. The sellers are either the origin servers or the peers who forward the digital multimedia content to their downstream peers. For each seller, the corresponding downstream peers play the role of buyers who are referred to as bidders. Each bidder submits a sealed bid to the corresponding seller. The highest bidder wins and pays its bid for the service. Also, we derive analytical closed-form expressions for upper bounds relevant to the performance metrics. The experimental validation proves the scalability and the efficiency of the proposed mechanism.     

IP组播及其核心技术探讨

简要阐述了IP组播实现机制,对IP组播核心技术研究现状及存在的问题作了初步的探讨,从而为这些技术以后的进一步研究提供了一定的参考依据。     

IP Multicast在校园网的实现

本文概要叙述了多播的机制，并给出了一个在以Alcatel Omnistack第三层交换机为核心的网络上实现多播的配置实例。     

计算机网络中的多播路由问题

在计算机网络中,多播是目前研究最多、应用最广的连接方式。就目前存在的多播路由算法及路由协议进行了分析与总结,给出了解决多播问题的一般方法,提出了在光网络中推行多播的必要性。     

Quick patching: an overlay multicast scheme for supporting video on demand in wireless networks

Many overlay multicast schemes have been proposed recently at the application level to support video-on-demand service over the Internet. With the proliferation of mobile devices and the increasing coverage of high speed wireless networks, such services are likely to be extended to support clients connected to the Internet through a wireless last hop. However, existing application level multicast schemes are not designed to handle the characteristics of the noisy wireless links. In this paper we propose an overlay multicast scheme called Quick Patching which arranges additional patch streams to clients under poor link conditions to improve their clients’ viewing quality. We demonstrate through extensive simulation experiments that Quick Patching is not only scalable, but can also sustain the required viewing quality under different network conditions including fluctuating error conditions as well as heterogeneous user viewing quality requirements.

C#中实现IP组播的关键技术

与单播技术相比,IP组播技术可以更有效地传输数据、降低网络负载,因而在视频、音频等多媒体数据传输中有着广泛的应用。C#是NET平台的代表性开发语言,利用C#实现组播有很好的应用前景。IP组播基于UDP协议,在C#开发语言中,可以通过UdpClient类的相关属性和方法来实现加入、退出组和传输组播数据。通过针对UdpClient类进行编程,并结合实际应用,一个基于局域网的组播实例被给出。     

在多协议标签交换组播中应用合并组播树

引入一种新的MPLS(多协议标签交换)组播实现方案——MPLS合并组播树,讨论了采用MPLS合并组播树在减少组播控制费用、故障恢复延迟、标签数等方面给MPLS组播带来的高效性,量化分析表明,采用MPLS合并组播树可以有效解决MPLS组播存在的标签数不足问题。     

移动Internet中的IP组播研究综述

随着组播应用的不断增加以及参与者的增多,组播领域的研究一直受到人们的广泛关注.而另一方面,近年来,移动设备迅速得到了普及,并且无线网络技术也得到了飞速的发展,因此,如何为移动主机提供更好的支持引起了人们的普遍关注.由于组播应用所具有的可扩展性强、高效等特点在移动这种资源受限的环境中显得尤为突出和重要,因此,移动环境中的组播应用引起了人们越来越多的重视,在该领域展开了大量的研究.详细地介绍了现有的主要移动组播算法和协议,讨论了每种算法或协议的适应范围以及优点,比较深入地剖析了其中存在的缺陷和问题,并且对这些移动组播算法和协议进行了综合对比.同时,特别针对移动环境可靠性较差的特点,对移动环境中进行可靠组播所面临的新问题以及相关研究现状进行了讨论.希望通过这些说明和对比,能够帮助研究者为其特定的需求选择适当的移动组播算法或协议.最后,讨论了移动环境中IP组播未来的研究方向.     

IPMulticast在多媒体远程安全监控系统中的应用

介绍了IPMulticast技术在多媒体远程安全监控系统中的应用,给出了整个监控系统的功能模块和系统框图,从分析整个多媒体远程安全监控系统中所需传输的数据类型出发,讨论了IPMulticast技术在整个监控系统中的应用,最后给出了相关的C 程序实现的源代码。     

基于MPEG-4 FGS视频的流式多播传输

根据流体流量控制机制和MPEG-4 FGS编码视频流精细分级的特点,提出了流式多播方法,该方法中数据不用分层组织且没有加入实验,极大地减少了网络开销.同时,针对视频图像组帧间编码的依赖关系,修正了视频质量PSNR的计算公式,较好地评价视频网络传输质量.对分层多播和流式多播的对比仿真实验表明,流式多播的性能稳定、扩展灵活,便于大规模扩展应用.