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。     

WDM网中光组播调度算法研究

介绍了用于WDM（波分复用）光网的两种组播调度算法，持续重传的随机选择和退避重传的随机选择，以及一种在同时到达的多个信息中进行选择的接收算法，并为它们建立了不同的数学模型，分析和比较了它们的性能。     

WDM网络中的光层组播技术

组播应用主要是一些带宽密集型的业务,而光网络又能够提供巨大的带宽。随着光通信技术的发展,如何在光层实现组播已经成为光网络研究的热点之一。主要介绍了组播的应用以及在光层实现组播的关键技术;分析了实现光层组播的节点结构、光树的概念以及针对组播的波长路由算法。     

稀疏分光网络中的组播路由机制研究

仅部分节点具有组播能力的光网络称为稀疏分光网络,基于网络性能和成本的考虑,网络常为稀疏分光配置.稀疏分光网络中组播路由主要解决如何为多点传送的组播业务请求寻找合适的光树或光森林的问题.在综合分类的基础上,文章重点对目前稀疏分光网络中的组播路由机制和相关算法进行分析和总结,并对未来工作进行了展望.     

WDM光网络广义无阻塞组播通信

文章讨论了一系列典型拓扑 (线阵列、环和网格 )WDM光网络的组播通信 ,并在常规路由算法下 ,导出了WDM网广义无阻塞组播通信时需求最小波长数的充要条件     

WDM网络中的光层组播保护

组播应用主要是一些带宽密集型的业务,而光网络又能够提供巨大的带宽.随着光通信技术的发展,在光层实现组播已经成为光网络研究的热点之一.主要讨论了在光层实现对组播业务的保护,对现有的保护方案进行了分类和比较研究,最后讨论了有待进一步研究的问题.     

WDM光网络中光层组播技术的研究

本文分析了光层组播原理。在物理层实现组播 ,使该技术在整个互联网实施实时交互音像通信和有效抑止“电子瓶颈”效应有着重大作用。文中对两种不同结构具有光层组播的OXC进行了分析比较。并且对WDM光网络中的无阻塞组播通信波长满足条件进行了分析探讨。     

IP组播技术原理及广东电信IP组播试验[1]

１组播技术概述组播（Multicast）又称为多播、多址广播、多地址广播和成组通信等，是相对于单播和广播方式而言的一种网络通信方式。IP组播技术作为IP网络中主机之间通信的一种模式，是通过组播地址寻址，向所有网络节点中某个确定子集（该子集被称为组播组）的成员发送数据包的技术。它的基本思想是源主机只需发送一份数据，属于该子集的所有接收者都可以收到相同的数据拷贝，而不属于该子集的主机则不能接收该数据拷贝。IP组播技术有效地解决了单点发送多点接收和多点发送多点接收等问题，实现了IP网络点到多点的高效数据传输。与传…     

IP组播技术分析与应用实现

介绍了一种IP组播的网络技术，分析了其工作机理及技术前提条件．并提供了使用Windows Sockets加入组播组从而进行发送、接收组播数据包的一整套方法。     

IP组播技术在视频中的应用

随着流媒体、视频等业务在Intemet上的相继开展，IP组播技术和应用开始快速发展。本文主要分析IP组播技术的产生、概念和特点，以及相关技术，最后介绍了IP组播技术在视频业务中的应用。     

Virtual Source Based Multicast Routing in WDM Optical Networks

Wavelength-division multiplexed (WDM) networks using wavelength-routing are considered to be potential candidates for the next generation wide-area backbone networks. Multicasting is the ability to transmit information from a single source node to multiple destination nodes and is becoming an important requirement in high-speed networks. As WDM technology matures and multicast applications become increasingly popular, supporting multicast routing at the WDM layer becomes an important and yet a challenging topic. This paper concerns with the problem of optical multicast routing in WDM networks. A few nodes in the network may have wavelength conversion and/or splitting capabilities. In this paper, a new multicast tree construction algorithm is proposed. This algorithm is based on a concept called virtual source. A virtual source is a node having both the splitting and wavelength conversion capabilities. By exploiting the presence of virtual source nodes, the proposed algorithm achieves improved performance. To further improve the performance, the algorithm assigns priorities to nodes based on their capabilities. The effectiveness of the proposed algorithm is verified through extensive simulation experiments.     

Protecting Multicast Sessions in WDM Networks with Sparse‐Splitting Constraints

In this letter, we study the multicast protection problem in sparse‐splitting wavelength‐division multiplexing (WDM) optical network, and propose a novel multicast protection algorithm called the shared source‐leaf path‐based protection (SLPP) algorithm. Unlike the proposals in previous studies, the backup paths derived by SLPP can share wavelength with the primary tree in sparse‐splitting WDM networks. Simulations are used to evaluate the effectiveness of the SLPP algorithm.     

WDM光网络中动态RWA算法仿真的实现

在WDM光网络中，在给定一组连接请求后，需要为之建立路由并分配波长，这被称为路由和波长分配问题（RWA）。由于当前光网络中的业务呈现爆炸式的增长，而光网络中的可用资源却是有限的，因此如何使用合理的RWA算法来优化网络资源的利用就显得尤为重要。目前已有很多文献提出了基于各种优化目标的RWA算法，也都通计算机仿真的方法测试和评估了算法的性能。计算机仿真是进行算法性能评估的主要手段，但是关于算法仿真的实现，—般的文献都涉及的很少，本文主要研究了WDM光网络中动态RWA算法计算机枋真的实现。     

Sparse Wavelength Conversion in Wavelength-Routed WDM Optical Networks*

A wavelength-routed optical network can suffer inefficiencies due to the wavelength-continuity constraint (under which a signal has to remain on the same wavelength from the source to the destination). In order to eliminate or reduce the effects of this constraint, a device called a wavelength converter may be utilized. Due to the high cost of these wavelength converters, many studies have attempted to determine the exact benefits of wavelength conversion. However, most of these studies have focused on optical networks that implement full wavelength conversion capabilities. An alternative to full wavelength conversion is to employ only a sparse number of wavelength converters throughout the network, thereby reducing network costs. This study will focus on different versions of sparse wavelength conversion--namely, sparse nodal conversion, sparse switch-output conversion, and sparse (or limited) range conversion--to determine if most of the benefits of full conversion can be obtained using only sparse conversion. Simulation and analytical results on these three different classes of sparse wavelength conversion will be presented. In addition, this study will present heuristic techniques for the placement of sparse conversion facilities within an optical network.     

Dynamic Multicast Session Provisioning in WDM Optical Networks with Sparse Splitting Capability

In this work, we study dynamic provisioning of multicast sessions in a wavelength-routed sparse splitting capable WDM network with an arbitrary mesh topology where the network consists of nodes with full, partial, or no wavelength conversion capabilities and a node can be a tap-and-continue (TaC) node or a splitting and delivery (SaD) node. The objectives are to minimize the network resources in terms of wavelength-links used by each session and to reduce the multicast session blocking probability. The problem is to route the multicast session from each source to the members of every multicast session, and to assign an appropriate wavelength to each link used by the session. We propose an efficient online algorithm for dynamic multicast session provisioning. To evaluate the proposed algorithm, we apply the integer linear programming (ILP) optimization tool on a per multicast session basis to solve off-line the optimal routing and wavelength assignment given a multicast session and the current network topology as well as its residual network resource information. We formulate the per session multicast routing and wavelength assignment problem as an ILP. With this ILP formulation, the multicast session blocking probability or success probability can then be estimated based on solving a series of ILPs off-line. We have evaluated the effectiveness of the proposed online algorithm via simulation in terms of session blocking probability and network resources used by a session. Simulation results indicate that our proposed computationally efficient online algorithm performs well even when a fraction of the nodes are SaD nodes.     

Optimal and heuristic algorithms for all‐optical group multicast in resource‐constrained WDM networks

Given a sparse‐splitting wavelength‐division multiplexing network with no wavelength converter, we study a group multicast problem that is how to transmit a number of multicast streams from the video server to multiple destinations simultaneously. To avoid the situation that the wavelengths are used up by the first few requests, one wavelength is available for each multicast request. Hence, some of destinations may not be included in the multicast trees because of the lack of wavelengths. Our goal is to construct a number of light trees with conflict‐free wavelengths for multiple requests so that the number of served clients is maximized. This problem is named as the revenue‐maximized and delay‐constrained group multicast routing problem. We first determine a set of multicast trees with the maximum number of served clients, then followed by the wavelength assignment to allocate the minimum number of wavelengths to the resulting trees. In this study, we propose two Integer Linear Programming ILP‐based algorithms for determining the optimal solutions for the light‐tree construction problem and the wavelength assignment problem, respectively. For large‐scale networks, two heuristics are introduced to solve the light‐tree construction problem approximately. A set of simulations are also provided for comparing performances of our algorithms against the other published methods. Copyright © 2016 John Wiley & Sons, Ltd.     

Scheduling Combined Unicast and Multicast Traffic in Broadcast WDM Networks

This paper studies the performance of various strategies for scheduling a combined load of unicast and multicast traffic in a broadcast WDM network. The performance measure of interest is schedule length, which directly affects both aggregate network throughput and average packet delay. Three different scheduling strategies are presented, namely: separate scheduling of unicast and multicast traffic, treating multicast traffic as a number of unicast messages, and treating unicast traffic as multicasts of size one. A lower bound on the schedule length for each strategy is first obtained. Subsequently, the strategies are compared against each other using extensive simulation experiments in order to establish the regions of operation, in terms of a number of relevant system parameters, for which each strategy performs best. Our main conclusions are as follows. Multicast traffic can be treated as unicast traffic, by replicating all multicast packets, under very limited circumstances. On the other hand, treating unicast traffic as a special case of multicast traffic with a group of size 1, produces short schedules in most cases. Alternatively, scheduling and transmitting each traffic component separately is also a good choice.     

On Finding the Multicast Protection Tree Considering SRLG in WDM Optical Networks

In this letter, a new sharing mechanism, SRLG sharing, is proposed, which allows the links of the same shared risk link group (SRLG) in a primary light tree to share protections in WDM optical networks. In previous studies, how to share spare resources with SRLG constraints has not been studied in multicast optical networks. In this letter, considering SRLG sharing, we propose a novel algorithm –multicast with SRLG sharing (MSS)– to establish a protection light tree. Finally, the algorithm MSS and the algorithm multicast with no SRLG sharing (MNSS) are compared through a simulation to show that our new sharing scheme of SRLG sharing is more efficient than that of no SRLG sharing in terms of spare resource utilization and blocking probability.     

多播格状WDM光网络中流量疏导的一种启发性算法

波分复用技术的开发应用及网络业务信息的多样化促进了多播技术的应用和发展.由于网络中波长带宽与节点间业务信息需求之间的巨大反差,使流量疏导成为必要,以节约网络资源和成本.但多播的出现使流量疏导算法变得更复杂多样.本文提出了对多播格状网络中的静态流量进行有效疏导的一种启发性算法,并取得较为优化的结果.     

光传送网技术及其进展

对光传送网有待解决的基本概念、技术及其进展进行了介绍 ,对光传送网可能采用的几种技术进行了比较并对有待解决的问题进行了阐述 ,最后在分析了国内外发展光传送技术状况的基础上 ,就我国开展光传送网络研究的建议提出个人的看法。