动态QoS多播路由协议

本文主要研讨了具有QoS约束的动态多播路由问题.文中描述了一种适用于QoS多播路由的网络模型,提出了一种动态QoS多播路由协议(DQMRP),该协议能操作在单播路由协议的顶层,它只要求网络链路(或节点)的局部状态信息,不需要维护全局状态信息.DQMRP可有效地减少构造一棵多播树的开销,多播组成员可动态地加入／退出多播会晤.该协议可搜索多条可行树枝,并能选择一条最优(或近优)树枝将新成员连接到多播树.文中给出了DQMRP的正确性证明和复杂性分析,并通过仿真实验验证了该协议的可用性和有效性.     

Bandwidth-satisfied multicast trees in large-scale ad-hoc networks

The purpose of this paper is to construct bandwidth-satisfied multicast trees for QoS applications in large-scale ad-hoc networks (MANETs). Recent routing protocols and multicast protocols in large-scale MANETs adopt two-tier infrastructures to avoid the inefficiency of the flooding. Hosts with a maximal number of neighbors are often chosen as backbone hosts (BHs) to forward packets. Most likely, these BHs will be traffic concentrations/bottlenecks of the network. In addition, since host mobility is not taken into consideration in BH selection, these two-tier schemes will suffer from more lost packets if highly mobile hosts are selected as BHs. In this paper, a new multicast protocol is proposed for partitioning large-scale MANET into two-tier infrastructures. In the proposed two-tier multicast protocol, hosts with fewer hops and longer remaining connection time to the other hosts will be selected as BHs. The objective is not only to obtain short and stable multicast routes, but also to construct a stable two-tier infrastructure with fewer lost packets. Further, previous MANET quality-of-service (QoS) routing/multicasting protocols determined bandwidth-satisfied routes for QoS applications. Some are implemented as a probing scheme, but the scheme is inefficient due to high overhead and slow response. On the contrary, the others are implemented by taking advantage of routing and link information to reduce the inefficiency. However, the latter scheme suffers from two bandwidth-violation problems. In this paper, a novel algorithm is proposed to avoid the two problems, and it is integrated with the proposed two-tier multicast protocol to construct bandwidth-satisfied multicast trees for QoS applications in large-scale MANETs. The proposed algorithm aims to achieve better network performance by minimizing the number of forwarders in a tree.     

一种新的QoS组播路由算法

针对现有的求解多约束QoS组播路由中存在的问题,结合BP神经网络局部搜索的优势和蚁群算法全局搜索的优势的特点,进行QoS组播路由算法的设计,提出了一种新型的NNAC算法。该算法通过BP神经网络寻找路径的更优解,改善了QoS组播路由路径寻找的方法。通过实验仿真表明,NNAC算法得到最优组播树的总延时为35,总代价费用为21,在完成150个度约束组播路由路径时,NNAC算法在进行最优组播树的寻找成功率上高于AC算法,同时该算法还克服了AC算法易陷入局部最小点的不足。     

A hexagonal-tree TDMA-based QoS multicasting protocol for wireless mobile ad hoc networks

The mobile multimedia applications have recently generated much interest in wireless ad hoc networks with supporting the quality-of-service (QoS) communications. The QoS metric considered in this work is the reserved bandwidth, i.e., the time slot reservation. We approach this problem by assuming a common channel shared by all hosts under a TDMA (Time Division Multiple Access) channel model. In this paper, we propose a new TDMA-based QoS multicast routing protocol, namely hexagonal-tree QoS multicast protocol, for a wireless mobile ad hoc network. Existing QoS routing solutions have addressed this problem by assuming a stronger multi-antenna model or a less-strong CDMA-over-TDMA channel model. While more practical and less costly, using a TDMA model needs to face the challenge of radio interference problems. The simpler TDMA model offers the power-saving nature. In this paper, we propose a new multicast tree structure, namely a hexagonal-tree, to serve as the QoS multicasting tree, where the MAC sub-layer adopts the TDMA channel model. In this work, both the hidden-terminal and exposed-terminal problems are taken into consideration to possibly exploit the time-slot reuse capability. The hexagonal-based scheme offers a higher success rate for constructing the QoS multicast tree due to the use of the hexagonal-tree. A hexagonal-tree is a tree whose sub-path is a hexagonal-path. A hexagonal-path is a special two-path structure. This greatly improves the success rate by means of multi-path routing. Performance analysis results are discussed to demonstrate the achievement of efficient QoS multicasting.     

QoS multicast routing by using multiple paths/trees in wireless ad hoc networks

In this paper, we investigate the issues of QoS multicast routing in wireless ad hoc networks. Due to limited bandwidth of a wireless node, a QoS multicast call could often be blocked if there does not exist a single multicast tree that has the requested bandwidth, even though there is enough bandwidth in the system to support the call. In this paper, we propose a new multicast routing scheme by using multiple paths or multiple trees to meet the bandwidth requirement of a call. Three multicast routing strategies are studied, SPT (shortest path tree) based multiple-paths (SPTM), least cost tree based multiple-paths (LCTM) and multiple least cost trees (MLCT). The final routing tree(s) can meet the user’s QoS requirements such that the delay from the source to any destination node shall not exceed the required bound and the aggregate bandwidth of the paths or trees shall meet the bandwidth requirement of the call. Extensive simulations have been conducted to evaluate the performance of our three multicast routing strategies. The simulation results show that the new scheme improves the call success ratio and makes a better use of network resources.     

Class-based multicast routing in interdomain scenarios

DiffServ-like domains bring new challenges to quality of service (QoS) multicast routing simply by shifting the focus from individual flows into classes of flows. Packets are marked at edge routers and receive differentiated treatment according to the class and not the flow that they belong to. DiffServ therefore became adverse to multicast, as packet replication inside the domain may require classification and remarking functions not present in core nodes. At the interdomain level, no doubt multicast QoS complexity is increased by the interleaving of DiffServ and non-Diffserv domains, making it more difficult to address QoS multicast in an end-to-end perspective. In today’s real interconnection world, classes of service have no meaning in certain links of a full interdomain path. While the problem is not new, as already pointed out, there are no real efforts to bring multicast back to a class-of-service domain without compromising its model of operation. In this article, we present an innovative multicast QoS routing strategy, clearly designed for the new class-of-service paradigm. The solution is based upon the construction of multiple trees, one per class of service available, while still allowing receivers to shift for source-specific trees in its own class of service. The strategy is presented in a full end-to-end perspective. Intradomain trees use differentiated routing paths thus helping traffic differentiation. Intradomain receivers are allowed to shift from shared trees into an adequate class-of-service source tree. At interdomain level, each class-of-service interdomain tree branch is accomplished by means of an improved path probing strategy enabling for QoS path establishment. This paper presents this new strategy, and associated protocols, for constructing several multicast and directed distribution trees, one per class of service, within each multicast group. This new strategy and associated protocols are then simulated using NS-2 platform. Simulation results are analyzed and compared with other multicast routing solutions, both at intra- and interdomain levels.     

QoS-aware multicast routing for the Internet: the design andevaluation of QoSMIC

One of the main problems of the current Internet infrastructure is its inability to provide services at consistent quality-of-service (QoS) levels. At the same time, many emerging Internet applications, such as teleeducation, and teleconferencing, require multicast protocols that will provide the necessary QoS. In this paper, we propose QoSMIC, a multicast routing protocol for the Internet, that provides QoS-sensitive paths in a scalable, resource-efficient, and flexible way. QoSMIC differs from the previous protocols in that it identifies multiple paths and selects the one that can provide the required QoS. Two other key advantages of QoSMIC are its flexibility and adaptivity. First, the distribution tree does not have to be rooted at a preselected core router. Second, we can tradeoff between efficiency metrics depending on our needs; for example, we can tradeoff routing efficiency for a reduction in the control messages. Extensive simulations show that our protocol improves the resources utilization and the end-to-end performance compared to the current protocols. Specifically, our protocol reduces the call blocking probability by a factor of six and reduces the end-to-end delay by as much as 90% compared to the PIM protocol     

Ad Hoc网络中基于协商机制的QoS多播路由研究

针对移动Ad Hoc网络QoS多播路由中普遍存在的拥塞问题,提出了一种基于协商机制的QoS多播路由协议,节点协商使用以一定QoS约束建立起的多播链路,避免过度使用多播资源引起网络拥塞,从而提高分组投递率和网络吞吐量。通过NS2仿真证明,该协议能够保证不同类型业务在网络中传输的服务质量,提高网络的利用率。     

An Efficient Multicast Routing Protocol in Wireless Mobile Networks

Providing multicast service to mobile hosts in wireless mobile networking environments is difficult due to frequent changes of mobile host location and group membership. If a conventional multicast routing protocol is used in wireless mobile networks, several problems may be experienced since existing multicast routing protocols assume static hosts when they construct the multicast delivery tree. To overcome the problems, several multicast routing protocols for mobile hosts have been proposed. Although the protocols solve several problems inherent in multicast routing proposals for static hosts, they still have problems such as non-optimal delivery path, datagram duplication, overheads resulting from frequent reconstruction of a multicast tree, etc. In this paper, we summarize these problems of multicast routing protocols and propose an efficient multicast routing protocol based on IEFT mobile IP in wireless mobile networks. The proposed protocol introduces a multicast agent, where a mobile host receives a tunneled multicast datagram from a multicast agent located in a network close to it or directly from the multicast router in the current network. While receiving a tunneled multicast datagram from a remote multicast agent, the local multicast agent may start multicast join process, which makes the multicast delivery route optimal. The proposed protocol reduces data delivery path length and decreases the amount of duplicate copies of multicast datagrams. We examined and compared the performance of the proposed protocol and existing protocols by simulation under various environments and we got an improved performance over the existing proposals.     

移动自组织网络中基于树结构的优化组播路由算法(英)

Mobile Ad hoc Networks(MANETs) play an important role in emergency communications where network needs to be constructed temporarily and quickly.Since the nodes move randomly,routing protocols must be highly effective and reliable to guarantee successful packet delivery.Based on the data delivery structure,most of the existing multicast routing protocols can be classified into two folders:tree-based and mesh-based.We observe that tree-based ones have high forwarding efficiency and low consumptions of bandwidth,and they may have poor robustness because only one link exists between two nodes.As a treebased multicast routing protocol,MAODV(Multicast Ad hoc On-demand Vector) shows an excellent performance in lightweight ad hoc networks.As the load of network increases,QoS(Quality of Service) is degraded obviously.In this paper,we analyze the impact of network load on MAODV protocol,and propose an optimized protocol MAODV-BB(Multicast Ad hoc On-demand Vector with Backup Branches),which improves robustness of the MAODV protocol by combining advantages of the tree structure and the mesh structure.It not only can update shorter tree branches but also construct a multicast tree with backup branches.Mathematical analysis and simulation results both demonstrate that the MAODV-BB protocol improves the network performance over conventional MAODV in heavy load ad hoc networks.     

QoS multicast routing in cognitive radio ad hoc networks

In this paper, we discussed the issues of QoS multicast routing in cognitive radio ad hoc networks. The problem of our concern was: given a cognitive radio ad hoc network and a QoS multicast request, how to find a multicast tree so that the total bandwidth consumption of the multicast is minimized while the QoS requirements are met. We proposed two methods to solve it. One is a two‐phase method. In this method, we first employed a minimal spanning tree‐based algorithm to construct a multicast tree and then proposed a slot assignment algorithm to assign timeslots to the tree links such that the bandwidth consumption of the tree is minimized. The other is an integrated method that considers the multicast routing together with the slot assignment. Extensive simulations were conducted to show the performance of our proposed methods. Copyright © 2011 John Wiley & Sons, Ltd.     

QoS routing through alternate paths in wireless ad hoc networks

Quality of service (QoS) routing plays an important role in QoS provisioning for mobile ad hoc networks. This work studies the issue of route selection subject to QoS constraint(s). Our method searches for alternate routes with satisfied QoS requirement(s) to accommodate each communication request when the shortest path connecting the source–destination pair of the request is not qualified. In order to effectively reduce protocol overhead, a directed search mechanism is designed to limit the breadth of the searching scope, which aims at achieving a graceful tradeoff between the success probability in QoS route acquisition and communication overhead. Efficient hop‐by‐hop routing protocols are designed for route selection subject to delay and bandwidth constraint, respectively. Simulation results show that the designed protocols can achieve high performance in acquiring QoS paths and in efficient resource utilization with low control overhead. Copyright © 2004 John Wiley & Sons, Ltd.     

Scalable Multicasting: The Core-Assisted Mesh Protocol

Most of the multicast routing protocols for ad hoc networks today are based on shared or source-based trees; however, keeping a routing tree connected for the purpose of data forwarding may lead to a substantial network overhead. A different approach to multicast routing consists of building a shared mesh for each multicast group. In multicast meshes, data packets can be accepted from any router, as opposed to trees where data packets are only accepted from routers with whom a tree branch has been established. The difference among multicast routing protocols based on meshes is in the method used to build these structures. Some mesh-based protocols require the flooding of sender or receiver announcements over the whole network. This paper presents the Core-Assisted Mesh Protocol, which uses meshes for data forwarding, and avoids flooding by generalizing the notion of core-based trees introduced for internet multicasting. Group members form the mesh of a group by sending join requests to a set of cores. Simulation experiments show that meshes can be used effectively as multicast routing structures without the need for flooding control packets.     

A scalable multicast routing protocol for building shortest path trees

Scalability is a great concern in the design of multicast routing protocols for the global Internet. Building shortest path trees (SPT) is currently one of the most widely used approaches to supporting multicast routing because of the simplicity and low per‐destination cost of such trees. However, the construction of an SPT typically involves high protocol overhead, which leads to the scalability problem as the number of concurrent multicast sessions increases. In this paper, we present a destination‐initiated shortest path tree (DSPT) routing protocol. The design objective is to effectively reduce the protocol overhead associated with SPT constructions for providing scalable multicast. To achieve this objective, we introduce destination‐initiated joining operations in constructing SPTs. With DSPT, each router receiving a request to join a specific multicast group makes a local decision on selecting its parent node through which it connects to the existing tree. A source‐rooted SPT is built as a result of such collaborative operations at nodes. DSPT requires only limited routing information at routers. Analytical results demonstrate that DSPT scales well with respect to computation, storage and communication overhead when the number of concurrent multicast requests is large. Simulation experiments are also conducted to verify the correctness of the theoretically deduced analytical results. Copyright © 2006 John Wiley & Sons, Ltd.     

无线Mesh网络组播研究分析

介绍了无线Mesh网络(WMN)中的组播协议,并分析了为WMN设计组播协议时要注意的一些因素,如Mesh路由器的有效性、多信道和信道分配的影响、负载均衡、组播路由性能指标的选择、保证QoS的影响和跨层优化.最后,分析了目前研究中存在的问题,并对未来的研究提出了自己的看法.     

一种基于带宽和时延约束的分布式组播路由算法

针对已有分布式组播路由算法在寻找QoS路由时的低成功率问题,本文提出了一种新的基于带宽和时延约束的分布式组播路由算法-QDMR(QoS-based Distributed Multicast Routing).在为新组播成员搜索连接到组播树的可行路径时,QDMR算法使用RBMF(Reverse Best Metric Forwarding)转发算法代替RPF(Reverse Path Forwarding)转发算法,从而优先搜索满足带宽和时延约束要求的路径,然后才考虑代价的优化.模拟分析表明,QDMR提高了路由搜索的成功率,并且降低了协议开销.     

Improved Shuffled Frog-Leaping Algorithm Based QoS Constrained Multicast Routing for Vanets

Prompt and reliable communication between vehicular nodes are essential as its limited coverage and dynamic mobility rate introduces frequent change of network topology. The key feature of vehicular communication that establishes direct connectivity or Road Side Unit-based data transfer among vehicular nodes is responsible for sharing emergency information during critical situations. Multicast routing data dissemination among vehicular nodes is considered to be the potential method of parallel data transfer as they facilitate the option of determining an optimal multicast tree from feasible number of multicast trees established between the source and destinations. This estimation of optimal multicast tree using meta-heuristic techniques is confirmed to improve the throughput and reliability of the network when QoS-based constraints are imposed during multicast routing. An Improved Shuffled Frog-Leaping Algorithm-Based QoS Constrained Multicast Routing (ISFLABMR) is proposed for estimating an optimal multicast tree that confirms effective multi-constrained applied multicast routing between vehicular nodes. ISFLABMR minimizes the cost of transmission to 22% by reducing the number of multicast clusters formed during multicasting through the utilization of local and global-based optimizations. The simulation results of ISFLABMR proveits predominant reduction rate of 24% and 21% in average packet latency and energy consumptions incurred under multicast routing.     

基于QoS的动态组播路由算法

在分析了网络中基于QoS的组播路由问题的基础上,本文提出了一种新的动态算法,并进行了实验和分析,文中构造的路由方案成功地解决了当网络中存在多个组播及组播节点动态变化情况下的QoS路由选择问题,此方案不仅保证了带宽,端到端延时和延时抖动,优化了路由树的代价,而且有效地控制了算法的复杂性并可适用于大规模的网络中。     

A resource‐tuned QoS multicast routing protocol

This paper presents a novel framework for quality‐of‐service (QoS) multicast routing with resource allocation that represents QoS parameters, jitter delay, and reliability, as functions of adjustable network resources, bandwidth, and buffer, rather than static metrics. The particular functional form of QoS parameters depends on rate‐based service disciplines used in the routers. This allows intelligent tuning of QoS parameters as functions of allocated resources during the multicast tree search process, rather than decoupling the tree search from resource allocation. The proposed framework minimizes the network resource utilization while keeping jitter delay, reliability, and bandwidth bounded. This definition makes the proposed QoS multicast routing with resource allocation problem more general than the classical minimum Steiner tree problem. As an application of our general framework, we formulate the QoS multicast routing with resource allocation problem for a network consisting of generalized processor sharing nodes as a mixed‐integer quadratic program and find the optimal multicast tree with allocated resources to satisfy the QoS constraints. We then present a polynomial‐time greedy heuristic for the QoS multicast routing with resource allocation problem and compare its performance with the optimal solution of the mixed‐integer quadratic program. The simulation results reveal that the proposed heuristic finds near‐optimal QoS multicast trees along with important insights into the interdependency of QoS parameters and resources.     

Forwarding state scalability for multicast provisioning in IP networks

Forwarding state scalability is one of the critical issues that delay the multicast deployment in IP networks. With traditional multicast routing protocols, a forwarding tree is built for each multicast session, and each router is required to maintain a forwarding entry for each multicast session whose distribution tree passes through the router. This poses the multicast forwarding state scalability issue when the number of concurrent multicast sessions is very large. We first present a survey of existing work addressing this scalability issue for providing scalable IP multicast. Then we extend an existing multicast routing protocol, Multicast Extension to OSPF (MOSPF), to scale well with respect to the number of concurrent multicast sessions by introducing tunnel support. This extension aims to reduce the protocol overhead associated with MOSPF. Simulation results show that the extension can significantly reduce multicast forwarding state and computational overhead at routers without affecting the per-destination shortest path characteristic of a resulting tree or introducing extra control overhead.