On the optimal multi-rate throughput for multicast with network coding

This paper investigates the maximal achievable multi-rate throughput problem of a multicast session at the presence of network coding. Deviating from previous works which focus on single-rate network coding, our work takes the heterogeneity of sinks into account and provides multiple data layers to address the problem. Firstly formulated is the maximal achievable throughput problem with the assumption that the data layers are independent and layer rates are static. It is proved that the problem in this case is, unfortunately, Non-deterministic Polynomial-time （NP）-hard. In addition, our formulation is extended to the problems with dependent layers and dynamic layers. Furthermore, the approximation algorithm which satisfies certain fair- ness is proposed.     

基于IPV6的组播路由协议PIM-SM的研究及实现

文章首先分析了研究IPv6组播技术的重要意义.然后详细分析了组播路由协议PIM-SM,并且在实验室生成IPv6环境下,对PIM-SM协议中的BSR选举、RP竞争、HelIo消息发布和数据流树切换等进行了测试,测试结果表明该协议工作正常,以其为基础实现的组播系统是正确的,符合RFC相关文档说明.     

一种最小化编码节点的网络编码优化算法

网络编码能有效地提升多播网络的传输性能,但编码的引入增加了节点的计算开销。为了克服网络编码带来的额外开销,该文提出了在代数网络编码框架下的网络编码优化模型,并在此模型基础上给出了基于改进遗传算法的最小化编码节点算法-(MCN,Minimizing Coding Nodes)。MCN在简单遗传算法的基础上增加了一些新的策略,避免了局部性问题和降低了算法寻优时间。模拟实验结果表明,MCN是有效的而且运行的更快,输出的网络编码方案所需要的编码节点也更少。同时将MCN应用到具有实际意义的网络中,同传统的网络编码相比,吞吐率仍可达到25%以上,而网络的平均延迟和网络开销却大大减少。     

WDM格型光网络中的动态组播共享保护算法

该文针对WDM格型网络中单链路失效的情况,提出了一种保护动态组播业务的基于路径的优化共享保护(PB-OSPM)算法。该算法在基于最优路径对的共享不相交路径(OPP-SDP)算法的基础上,通过引入保护波长使用情况矩阵和波长预留矩阵记录预留波长资源的使用情况,允许不发生冲突的不同组播的保护路径间共享预留波长资源。研究采用欧洲光网络(EON)的拓扑对PB-OSPM算法和OPP-SDP算法在增性网络负载情况下的网络冗余度和同波长资源配置和网络负载情况下动态网络负载的网络连接阻塞率做了仿真。结果表明,相同条件下,PB-OSPM算法比OPP-SDP算法有更低的连接阻塞率。组播业务间波长资源的共享是提高波长资源利用率的有效方法。     

基于QoS保证的广播/组播OFDM系统资源分配策略

该文提出了一种基于服务质量(QoS)保证的次优广播/组播OFDM系统资源分配算法。算法在最优分配原则的基础上采用不同广播/组播业务目标速率作为约束条件,并以业务组中最差接收用户传输速率作为搜索目标,使得业务组中全部用户达到QoS要求,算法的公平性及有效性得到提高;同时采用时频格作为分配算法中的基本资源单位,以降低分配算法的复杂度。仿真结果表明,改进分配策略的系统吞吐量性能接近最优广播/组播分配算法,提高了广播/组播系统资源分配的公平性。     

Fairness of sharing protection for multicast in WDM networks

In this paper, the sharing schemes of multicast in survivable Wavelength-Division Multiplexed （WDM） networks are studied and the concept of Shared Risk Link Group （SRLG） is considered. While the network resources are shared by the backup paths, the sharing way is possible to make the backup paths selfish. This selfishness leads the redundant hops of the backup route and a large number of primary lightpaths to share one backup link. The sharing schemes, especially, the self-sharing and cross-sharing, are investigated to avoid the selfishness when computing the backup light-tree. In order to decrease the selfishness of the backup paths, it is important to make the sharing links fair to be used. There is a trade-off between the self-sharing and cross-sharing, which is adjusted through simulation to adapt the sharing degree of each sharing scheme and save the network resources.     

基于遗传算法的全光组播路由

该文提出使用遗传算法优化组播业务放置进光网络的顺序,按照此顺序为业务构建组播树并选择波长,以最小化光网络中使用的波长数及组播链路数。比较了3种路由算法的优劣以及波长变换器对资源优化的改善作用。基于NSFNet网络的仿真证明组播能力节点只需占到全网节点数的一半就能达到很好的优化效果。     

k元n方网络中的优化多播策略

该文提出了一种在基于虫孔交换的k元n方网络中实现并发多播通信的有效策略。该策略通过引入分区的概念,把整个网络划分成多个通信区域而提高了多播的并行性。在该策略下,结合自适应单播路由生成的多播路由算法能够实现低延迟,低标准差和高吞吐率的多播通信,且不需要引入任何附加硬件需求。该文给出了在512个节点的三维torus网络中的仿真结果,验证了该策略的有效性。     

Minimizing Intermediate Multicast routing for dynamic multi-hop ad hoc networks

A Minimizing Intermediate Multicast Routing protocol （MIMR） is proposed for dynamic multi-hop ad hoc networks. In MIMR, multicast sessions are created and released only by source nodes. In each multicast session process, the source node keeps a list of intermediate nodes and destinations, which is encapsulated into the packet header when the source node sends a multicast packet. Nodes receiving multicast packets decide to accept or forward the packet according to the list. Depending on topology matrix maintained by unicast routing, the shortest virtual hierarchy routing tree is constructed by improved Dijkstra algorithm. MIMR can achieve the minimum number of intermediate nodes, which are computed through the tree. No control packet is transmitted in the process of multicast session. Load of the network is largely decreased. Experimental result shows that MIMR is flexible and robust for dynamic ad hoc networks.     

下一代网络中基于遗传算法的QoS组播路由算法

向用户提供多媒体业务是下一代网络业务最基本、最重要的要求,QoS组播路由技术是网络多媒体信息传输的核心技术之一。该文给出了支持QoS组播的网络模型,对已有的QoS组播路由算法进行了优化,提出了适用于下一代网络的基于遗传算法的QoS组播路由算法。仿真实验表明,这种算法收敛速度快,可靠性高,能够很好地满足下一代网络QoS组播的需求。