IP组播技术原理及广东电信IP组播试验[2]

2.2跨域方式下组播的实现1992年3月第一个组播主干网MBONE（MulticastBONE）采用的是DVMRP，为了能在Internet上实现大范围的组播，必须采用DVMRPTunnel方式将各个开通组播的区域连接起来。但由于DVMRP采用FloodandPrune方式，并且由于该协议基于RIP协议，因此它并不适于大范围的组播应用。现阶段大范围组播是通过跨域组播方式实现的，它以PIM-SM为基础，通过MBGP（MultiprotocolBorderGate鄄wayProtocol，多协议边界网关协议）和MSDP（MulticastSourceDiscoveryProtocol，组播源发现协议）实现。在跨域组播方式下，…     

基于名字映射和解析系统的多RP组播

大量以信息为中心的应用使得组播再次受到关注。基于共享树的组播方法相较于基于源树的组播方法能够有效地减少组播转发状态,但仍存在一些问题,如RP管理复杂、RP负载过大、传输时延高和流量汇聚等。基于此,文中提出了一种基于名字映射和解析系统（NMRS）的多RP组播方法。针对RP管理复杂和过载问题,所提方法将所有路由器都作为候选RP,并使用NMRS管理候选RP以实现负载均衡。针对时延过高的问题,所提方法使用现场名字映射和解析服务维护局部源信息并为局部的源选择最近的RP,每个组播组建立多个以不同RP为根的共享树。实验结果表明,相较于现有基于共享树的方法,所提的组播方法在仅增加部分组播转发状态的同时能够有效减少RP负载、传输时延和流量汇聚。     

IP网组播的实现机制（下）

广域网上的组播实现有多种技术方式，但是最常用的实现方式是采用PIM—SM组播路由协议。PIM—SM协议与单播路由协议无关，并可同时支持基于源的组播树和共享树两种组播方式，特别是它是实现跨AS域组播的基础。因此，当前多数网络是以PIM—SM作为其组播路由协议。下面，将针对实例详细介绍PIM—SM的组播实现方式。     

无线传感器与执行器网络组播技术研究

组播是将给定消息从一个源节点发送到若干个目标节点的通信模式。在组播中,给定消息沿着路由从一个节点发送到多个目标节点,这些目标节点的位置是任意的,且分布在整个网络内。文章给出了WSAN(无线传感器与执行器网络)中组播的定义与数学描述,分析了Ad hoc网络组播协议以及基于树与网格的组播协议特征与思路,描述了LAM(轻量级自适应组播)、DDM(差异目标组播)、GMP(地理组播协议)、PBM(基于位置的组播)、GMR(地理组播路由)、HRPM(分层汇聚点组播)、HGMR(分层地理组播路由)等地理组播协议的工作原理。     

基于Agent实现组播在广域网中的传输

针对目前Internet中大部分路由器不支持组播数据传输的问题，本文基于Agent技术提出了一种实现广域网内组播数据传输的方法。该方法使用了基于Agent的通信模型．组播会话中的每个成员通过其上运行的Agent实现数据收发；并将能够实施IP组播通信的网络范围看作是一个组播域，在每个组播域中自动选择一个Agent作为主Agent(MA)，组播域中的其他Agent为备份Agent(BA)；在组播域内利用IP组播进行数据传输，在组播域间利用主Agent之间的TCP连接进行数据传输．从而使得组播通信能够跨越路由器的障碑。此外还实现了BA向MA的自动升级．保证了组播会话的可靠性和连续性。     

基于多上游接口MLD代理的移动组播

RFC6224是在PMIPv6域中支持组播接收者移动的部署方案。此方案中移动接入网关（MAG）上部署的多实体组播侦听发现（MLD）代理会造成冗余的组播数据到达MAG,产生“隧道汇聚”问题。为此,提出一种基于多上游接口MI。D代理的解决方法。该方法对传统的MLD代理进行改进,把单一的上游接口改造成多上游接口,并使用“显式追踪”功能记录下游接口的组成员状态信息,从根本上解决“隧道汇聚”问题。对比分析结果显示,提出的移动组播方案与MULTIMOB工作组中的纽播树移动锚点移动组播、直接路由移动组播和PMIPv6扩展移动组播方案相比更具优势。     

WDM层实现IP组播

WDM Multicast的关键问题是如何在WDM层建立组播树。本文深刻分析WDM网络上实现组播所面临的难题，并指出其与传统的IP组播的区别。在此基础上提出了两种可行的WDM Multicast方案。一种是对现有组播协议不加修改，但是需要增加一个中间层来实现WDM层组播树的构建；另外一种修改现有组播路由协议，使其充分考虑到WDM层的光分路能力，并设计新的波长路由分配算法来建WDM层组播树。本文对这两种方案详细分析并以目前广泛使用的DVMRP协议为例来说明它们各自的特点。     

IP组播技术原理及广东电信IP组播试验[3]

４典型设备配置４郾１RP的配置对于PIM－SM而言，最根本的就是进行RP的设置。由于组播协议统一采用PIM－SMV２，因此我们利用BSR方式来确定RP。Cisco路由器上的具体配置如下：＜config＞＃ipmulticast－routingdistributed／设置启用组播路由，使Cisco的IOS软件能够转发组播数据包；distribut鄄ed参数用于启动MDS（MulticastDistributedSwitching），Cisco路由器中只有７５００系列和GSR系列支持该功能／＜config＞＃interfaceLoopback０＜config－if＞＃ippimsparse－mode／设置稀疏模式／在PIM中，一个接口可以是Sparse模…     

基于消息认证码的安全有效的组播源认证

组播通信正成为不断增长的应用基础，而其关键是要为组通信提供可靠的安全机制，然而，现有的组播安全协议仅能提供部分的解决方法，考虑到源认证是组的最主要安全事务之一，文章基于消息认证码提出了一种安全有效的组播源认证方法。     

一种组播源发现协议MSDP的实现方案

在分析MSDP协议工作机制的基础上,给出了一种协议的实现方案。该方案将协议分为peer连接模块、报文处理模块、定时器模块以及外部接口模块并加以实现,适合在核心路由器中采用来支持域间组播功能。     

A Domain-Based Routing Protocol for SSM Source Mobility in Mobile IPv6 Networks

In Mobile IP, the signaling traffic overhead will be too high since the new Care-of-Address (CoA) of the mobile node (MN) is registered all the way with the home agent (HA) whenever the MN has moved into a new foreign network. To complement Mobile IP in better handling local movement, several IP micro protocols have been proposed. These protocols introduce a hierarchical mobility management scheme, which divides the mobility into micro mobility and macro mobility according to whether the host's movement is intra-domain or inter-domain. Thus, the requirements on performance and flexibility are achieved, especially for frequently moving hosts. This paper introduces a routing protocol for multicast source mobility on the basis of the hierarchical mobile management scheme, which provides a unified global architecture for both uni- and multicast routing in mobile networks. The implementation of multicast services adopts an improved SSM (Source Specific Multicast) model, which combines the advantages of the existing protocols in scalability and mobility transparency. Simulation results show that the proposed protocol has better performance than the existing routing protocols for SSM source mobility.     

Rendezvous Point Relocation in Protocol Independent Multicast-Sparse Mode

Protocol Independent Multicast-Sparse Mode is the most widely used multicast routing architecture. It builds a shared distribution tree centered at a rendezvous point and then builds source-specific trees for those sources whose data rate warrants it. Current implementations of the protocol decide on the rendezvous point administratively, which leads to congestion and delays. An attractive solution would be dynamic relocation of the rendezvous point depending on the members of the multicast group. In this paper we present a rendezvous point calculation and relocation mechanism for Protocol Independent Multicast-Sparse Mode. Simulation of the proposed mechanisms is used to demonstrate the effectiveness of the proposals.     

Fast adaptive routing supporting mobile senders in Source Specific Multicast

IP multicast deployment recently progresses, but group services often remain restricted to limited domains and fail to comply with route-optimizing mobility management of the next generation Internet. Source Specific Multicast (SSM) facilitates transparent inter-domain routing and is expected to globally disseminate to many users and services. However, mobility support for Source Specific Multicast is still known to be a major open problem. In this paper, we propose the Enhanced Tree Morphing (ETM) protocol for extending SSM routing to mobile multicast sources. The scheme dynamically adapts SSM forwarding states to sender mobility, and transforms (morphs) source specific distribution trees into new, optimal trees rooted at a relocated source. ETM is simple, robust and secure, while it admits superior performance in packet forwarding at a low signaling overhead. Extensive evaluations based on a full protocol implementation, and simulations based on real-world topology data are performed, granting full insight into the properties of packet loss and delay stretch, protocol convergence times and router state evolution during single and rapidly repeated handovers. In a constant bit rate scenario, an ETM source handover typically leads to a slightly increasing delay of the first data packet, only. When operating on realistic network topologies, the protocol uniformly converges within less than 50 ms, thereby sustaining robustness under rapid source movement at all speeds common to our mobile world. Further optimizations are identified for FMIPv6 and for multihomed nodes.     

局域网组播的IGMP扩展认证模型设计

互联网组播技术可以从根本上改善网络带宽的利用率,使发送者和路由器的处理消耗以及发送延迟降到最低的程度。IGMP是一种应用比较广泛的组播用户组管理协议,但是本身没有认证功能。PAP（密码认证协议）提供了一种简单的可以使端对端使用2次握手建立身份验证的协议。论文提出一种IGMP改进方案,把PAP认证协议添加在IGMP v3协议的扩展字段中,用于组播路由的最后一跳认证。     

组播通信的访问控制和密钥管理

IP组播是一种高效的多目标传输机制.随着网络的发展,组播在网络的应用占据着越来越重要的地位,其应用不断扩展,技术日益成熟.目前,组播作为一个崭新的学术研究领域,在组播路由算法、流量控制、可靠传输等方面的研究已有很多成果,而对于组播安全问题的研究特别是组播通信密钥的研究还很不成熟.本文通过研究绀播通信安全进行深入的研究,对比各种密钥管理方法,研究了可扩展的密钥管理方法.该密钥管理体系采用分层管理结构,采用子管理中心对各个子域进行管理,不仅可以高效地处理组播组成员动态加入和退出,同时,大大减少了密钥管理中心的负担.使该方法可以应用于大型、动态的组播系统.此外,该方法根据现有的网络和组播系统的要求,提出了控制中心由计算机组进行统一调度管理,避免了单点故障的问题,增加了系统的鲁棒性.     

Probabilistic reliable multicast in ad hoc networks

When striving for reliability, multicast protocols are most commonly designed as deterministic solutions. Such an approach seems to make the reasoning about reliability guarantees (traditionally, binary, “all-or-nothing”-like) in the face of packet losses and/or node crashes. It is however precisely this determinism that tends to become a limiting factor when aiming at both reliability and scalability, particularly in highly dynamic networks, e.g., ad hoc networks. Gossip-based multicast protocols appear to be a viable path towards providing multicast reliability guarantees. Such protocols embrace the non-deterministic nature of ad hoc networks, providing analytically predictable probabilistic reliability guarantees at a reasonable overhead.

This paper presents the Route Driven Gossip (RDG) protocol, a gossip-based multicast protocol designed precisely to meet a more practical specification of probabilistic reliability in ad hoc networks. Our RDG protocol can be deployed on any basic on-demand routing protocol, achieving a high level of reliability without relying on any inherent multicast primitive. We illustrate our RDG protocol by layering it on top of the “bare” Dynamic Source Routing protocol, and convey our claims of reliability and scalability through both analysis and simulation.     

A Study of Broadband Intelligent Network Implementing Video Conference and Multicast Routing Algorithm

A Study of Broadband Intelligent Network Implementing Video Conference and Multicast Routing Algorithm     

An efficient mesh‐based multicast routing protocol in mobile ad hoc networks

Mesh‐based multicast routing protocols for mobile ad hoc networks (MANETs) build multiple paths from senders to receivers to deliver packets even in the presence of links breaking. This redundancy results in high reliability/robustness but may significantly increase packet overhead. This paper proposes a mesh‐based multicast protocol, called centered protocol for unified multicasting through announcements (CPUMA), that achieves comparable reliability as existing mesh‐based multicast protocols, however, with significantly much less data overhead. In CPUMA, a distributed core‐selection and maintenance algorithm is used to find the source‐centric center of a shared mesh. We leverage data packets to center the core of each multicast group shared mesh instead of using GPS or any pre‐assignment of cores to groups (the case of existing protocols). The proposed centering scheme allows reducing data packet overhead and creating forwarding paths toward the nearest mesh member instead of the core to reduce latency. We show, via simulations, that CPUMA outperforms existing multicast protocols in terms of data packet overhead, and latency while maintaining a constant or better packet delivery ratio, at the cost of a small increase in control overhead in a few scenarios. Copyright © 2010 John Wiley & Sons, Ltd.     

New Approach to Inter‐domain Multicast Protocols

IPTV broadcast channels and video content distribution are increasingly saturating network paths. New solutions based on inter‐domain multicast protocols could contribute to the enhancement of multimedia content distribution over the Internet. The aim of this paper is to propose new capabilities for an existing inter‐domain multicast protocol, the Protocol Independent Multicast‐Sparse Mode. We describe the modified protocol and analyze its behavior using newly developed tools based on an open‐source software simulator. The resulting protocol does not require topology information, which is advantageous for easier deployment. In addition, the adopted solution avoids inherent problems with inter‐domain multicast routing, such as multiple paths and path asymmetries.     

Scalable team multicast in wireless ad hoc networks exploiting coordinated motion

In this paper, we study a new multicast paradigm for large scale mobile ad hoc networks, namely team multicast. In team multicast the multicast group does not consist of individuals, rather, of member teams. For example a team may be a special task force that is part of a search and rescue operation. The message must be broadcast to each member of each team in the multicast group. Team multicast is very common in ad hoc networks set up to accomplish some collective tasks, such as for emergency recovery or battlefield applications. A key problem in several of the above applications is scalability to large membership size as well as network size. Our approach exploits motion affinity (more precisely, team members’ coordinated motion) which is typically present when the set of nodes has a commonality of interests. Each team can be viewed as a logical subnet. Within the team a landmark node is dynamically elected. The addresses of and the paths to the chosen landmarks are propagated into the whole network so that a source of a multicast group can route to the landmark of a subscribed team.Our protocol, Multicast-enabled Landmark Ad Hoc Routing (denoted as M-LANMAR), uses tunneling from multicast sources to each landmark of the subscribed team and restricted flooding within the motion group. Simulation study shows that M-LANMAR provides efficient and reliable multicast compared with the application of a “flat” multicast scheme (e.g., ODMRP) that does not exploit team coordinated motion.This paper contains three contributions: a new model for team multicast, with the definition of team dynamics (join, merge, split); the exploitation of team mobility and of landmarks in order to achieve scalable multicast, and; the implementation and performance evaluation of M-LANMAR, a landmark based team multicast scheme.