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.     

基于相交多路径的组播主动式恢复方案

提出了基于相交多路径的组播主动式恢复方案。该方案通过为树中节点提供备用父节点的方式,计算组播源到各个组成员的多条相交路径来代替不相交双树。相交多路径保证了构建成功率并为组播路由提供一定程度的保护。仿真结果表明,该方案构建的组播树以及故障恢复后组播树的代价均与现有方案相当,但是提供的故障恢复时间与现有方案相比显著缩短。     

A new high performance approach: merging optimal multicast sessions for supporting multisource routing

Each single source multicast session (SSMS) transmits packets from a source node s _i to a group of destination nodes t _i , i=1,2,…,n. An SSMS’s path can be established with a routing algorithm, which constructs multicast path between source and destinations. Also, for each SSMS, the routing algorithm must be performed once. When the number of SSMS increases to N≥2, the routing algorithm must be separately performed N≥2 times because the number of source nodes increase to N≥2 (for each SSMS the routing algorithm must be performed once). This causes that time of computation and bandwidth consumption to grow. To remove this problem, in this paper, we will present a new approach for merging different SSMSs to make a new multicast session, which is performed only with one execution of a routing algorithm. The new approach, merging different sessions together, is based on the optimal resource allocation and Constraint Based Routing (CBR). We will show that as compared to other available routing algorithms, it improves time of computation and bandwidth consumption and increases data rate and network efficiency. The new approach uses CBR and merges more than one single source multicast session (SSMS) problem to one multisource multicast session (MSMS) problem. By solving one MSMS problem instead of solving more than one SSMS, we can obtain an optimal solution that is more efficient than optimal solutions of SSMS problems.     

基于延时影响因子的应用层多播ASD模型改进研究

为提高应用层多播的稳定性和效率,在原ASD-TS模型上加以改进,提出一种基于延时因子的ASD-DIF模型。该模型可以在新节点探测整个多播网络的基础上自主选择加入方式,使新节点给整个多播组带来的延时最小,构建高效率、高分发度的多播树。仿真实验表明ASD-DIF模型在构建多播网络的时候能够构建高效率的转发路径,有效降低多播的时延。     

Distributed Searching of Multi-dimensional Data: A Performance Evaluation Study

In this paper we present a data structure for searching in multi-dimensional point sets in distributed environments and discuss its experimental evaluation also through a comparison with previous proposals. The data structure is based on an extension ofk-d trees. The technological reference context is a distributed environment where multicast (i.e., restricted broadcast) is allowed, but it is also shown how to avoid using it. The data structure supports exact, partial, and range search queries with a complexity that is optimal in a distributed sense. The set of multidimensional points is managed in a scalable way, i.e., it can be dynamically enlarged with insertion of new points. We also propose new performance measures for the comparative evaluation of the efficiency with which a data structure is distributed over a communication network.     

TMA: Trajectory-based Multi-Anycast forwarding for efficient multicast data delivery in vehicular networks

This paper describes Trajectory-based Multi-Anycast forwarding (TMA), tailored and optimized for the efficient multicast data delivery in vehicular networks in terms of transmission cost. To our knowledge, this is the first attempt to investigate the efficient multicast data delivery in vehicle networks, based on the trajectories of vehicles in the multicast group. Due to the privacy concern, we assume only a central server knows the trajectory of each vehicle and the estimated current location of the vehicle. Therefore, after receiving a request of multicast data delivery from a source vehicle, the central server has to figure out how the data has to be delivered to the moving vehicles in the multicast group. For each target vehicle in the multicast group, multiple packet-and-vehicle rendezvous points are computed as a set of relay nodes to temporarily hold the data, considering the vehicle’s trajectory. This set of rendezvous points can be considered an Anycast set for the target vehicle. We have formulated the multicast data delivery as the data delivery to the anycast sets of the multicast group vehicles. Through theoretical analysis and extensive simulation, it is shown that our design provides an efficient multicast for moving vehicles under a variety of vehicular traffic conditions.     

基于MAPE结构的组播AAA模型

指出了现有组播协议存在的安全性问题，提出了一种基于MAPE的组播服务AAA模型，给出了该结构下的核心模块组播敏感第二层交换机的内部结构和工作原理，并阐明这种体系结构对于在城域网范围内开展有偿组播服务的重要意义。     

Dynamic overlay multicast for live multimedia streaming in urban VANETs

Infotainment service has been a foreseeing trend in VANETs (Vehicular Ad Hoc Networks), and multimedia streaming has a high potential in VANET infotainment service. This paper considers the scenario of live multimedia streaming multicast to vehicles of the same group using a dynamic application layer overlay. Due to the willingness for cooperation of non-group nodes, application layer overlay multicast is more feasible than other kinds of multicast such as network-coding-based multicast and network-layer multicast. To adapt to high mobility and full of obstacles in urban VANETs, we propose an effective dynamic overlay multicast scheme for multimedia streaming, called OMV (Overlay Multicast in VANETs). The proposed OMV enhances an overlay’s stability with two strategies: (1) QoS-satisfied dynamic overlay and (2) mesh-structure overlay. The QoS-satisfied strategy to adjust the overlay selects potential new parents based on their streams’ packet loss rates and end-to-end delays. The mesh-structure strategy allows a child to have multiple parents. We evaluate the proposed OMV in urban VANETs with obstacles using two real video clips to demonstrate the feasibility of the OMV for real videos. Evaluation results show that comparing the proposed OMV to Qadri et al.’s work, which is a static mesh overlay and is the best method available in VANETs, the packet loss rate is reduced by 27.1% and the end-to-end delay is decreased by 11.7%, with a small control overhead of 2.1%, on average. Comparing the proposed OMV for tree overlays to ALMA, which is for dynamic tree multicast overlays and is also the best method available in MANETs, the packet loss rate is reduced by 7.1% and the end-to-end delay is decreased by 13.1%. In addition, to address the problem of obstacle-prone urban VANETs, we also derive feasible stream rates and overlay sizes for city maps with different road section sizes. To the best of our knowledge, how to organize and dynamically adjust an application layer multicast overlay for live multimedia streaming have not been studied in existing VANET literatures. In summary, to deal with highly dynamic topologies in urban VANETs, we propose a QoS-satisfied strategy for group nodes to switch to new parents that can offer better QoS. The proposed OMV is feasible for live multimedia streaming applications, such as emergency live video transmission and live video tour guides for passengers in different vehicles that belong to the same multicast group.     

MPLS网络中的可扩展QoS组播研究

MPLS网络中的服务质量组播面临着组播路由状态的可扩展性、服务质量支持困难等瓶颈.针对这些问题,提出一种基于子树共享的新型MPLS服务质量组播方案.本文的贡献有:提出一种组播组到组播分发子树的映射算法,将多个组映射到同一颗子树,以共享的子树为基础构造完整的组播分发树,从而有效地减少MPLS核心网络中的路由状态;将服务质量的考量引入组播分发树的构造过程中,使新的方案能够支持服务质量组播;提出一种简单方便的子树共享实现机制.模拟结果表明,基于子树共享的新型MPLS服务质量组播方案能够有效地减少组播路由状态并提供多种服务质量控制的能力.     

Strategies for Path-Based Multicasting in Wormhole-Routed Meshes

Multicasting is an information dissemination problem which consists, for a processor of a distributed memory parallel computer, in sending the same message to a subset of processors. In this paper, we propose new multicast algorithms for a mesh network usingwormholerouting with apath-basedfacility. These new algorithms generally perform faster than algorithms previously described in the literature under the same model. We used as the criteria for comparing algorithms theoff-line computation timenecessary to prepare the multicast and thecommunication timerequired to complete the multicast.     

基于环覆盖网络的端系统组播方法

针对传统组播方法难于维护的问题,提出一种基于环覆盖网络的端系统组播方法,按照节点之间的延迟将它们组织成不同的延迟聚集环,在此基础上进行组播,无须对每个多播源单独构建多播树,从而更好地适应多播成员的动态变化。仿真实验结果表明,该方法能够使延迟的变化随着节点数目的增大而趋于平稳。     

GMAC: An overlay multicast network for mobile agent platforms

The lack of proper support for multicast services in the Internet has hindered the widespread use of applications that rely on group communication services such as mobile software agents. Although they do not require high bandwidth or heavy traffic, these types of applications need to cooperate in a scalable, fair and decentralized way. This paper presents GMAC, an overlay network that implements all multicast related functionality–including membership management and packet forwarding–in the end systems. GMAC introduces a new approach for providing multicast services for mobile agent platforms in a decentralized way, where group members cooperate in a fair way, minimize the protocol overhead, thus achieving great scalability. Simulations comparing GMAC with other approaches, in aspects such as end-to-end group propagation delay, group latency, group bandwidth, protocol overhead, resource utilization and failure recovery, show that GMAC is a scalable and robust solution to provide multicast services in a decentralized way to mobile software agent platforms with requirements similar to MoviLog.     

Comparison of recovery schemes to maximize restorable throughput in multicast networks

Multicast networks have many applications especially in real-time content delivery systems. For high-quality services, users do not expect to witness any interruption; thus, network link failure has to be handled gracefully. In unicast networks there are many approaches for dealing with link failures using backup paths. Recently, Cohen and Nakibly categorized these methods, provided linear programming formulations for optimizing network throughput under the assumption that the paths are splitable, and compared them experimentally. In this work, we take their approach and apply to the multicast failure recovery problem. We propose backup bandwidth allocation algorithms based on linear programs to maximize the throughput, and perform an experimental study on the performance of recovery schemes. We study many recovery schemes in multicast networks and propose a new recovery scheme that performs better than all other recovery scheme except the one that recomputed the whole multicast tree from scratch for each link failure.     

移动自组网络中简单组播转发协议的扩展

简单组播转发协议在没有接收者时,组播源也会洪泛整个网络,这样就会产生不必要的重复数据．为了避免在移动白组网中出现这种问题,作者针对简单组播转发协议提出了一种扩展方法,即根据有限的洪泛范围和到达所有组播接收者的单播,对组播源列表中的每个接收者计算一个混合值．以这个混合值为标准选择有限的洪泛方式与单播方式的最佳组合来最小化洪泛带来的网络开销．     

Distributed dynamic mobile multicast

Traditional mobile multicast schemes have either high multicast tree reconfiguration cost or high packet delivery cost. The former affects service disruption time while the latter affects packet delivery delay. Although existing region-based mobile multicast schemes offer a trade-off between two costs to some extent, most of them do not determine the size of the service range, which is critical to network performance. In this paper, we propose a novel approach, called Distributed Dynamic Mobile Multicast (D²M²), to dynamically determine the optimal service range according to the mobility and service characteristics of a user. We derive an analytical model to formulate the costs of multicast tree reconfiguration and multicast packet delivery. The model is based on a Markov chain that analyzes a mobile node’s movement in a 2D mesh network. As the complexity of computing steady probability is high, we aggregate the Markov states by leveraging mobility symmetry. Simulation shows that the network performance is enhanced through D²M².     

受时延约束的组播路由算法

提出了一种新的受时延约束的组播路由算法。算法借鉴了MPH算法的思想,最初的组播树只包含源结点,然后每次将到达组播树的代价最小且满足时延约束的结点及其相应的路径加入到组播树,直到所有的成员加入为止。谊算法能够快速地得到一棵满足时延约束的组播树,并且组播树的代价也很小。实验表明：该算法简单,复杂度低,性能良好,易于在分布式环境中实现,可应用于实际的应用系统中。     

MSN网络的优化问题研究

研究了由MSN节点组成的应用层组播网络,讨论了度约束最小直径生成树(D-MDST)问题,并给出了求解该问题的BCT算法。提出了一种新的生成树编码方法——过程控制编码,该编码将启发式算法与遗传算法结合起来且具有编码简单、译码方便、适用常规遗传算子等优点。给出了基于该种编码的遗传算法,并将BCT算法作为过程控制编码的译码器。仿真结果表明了该遗传算法的有效性。     

Dynamic multicast routing algorithm for delay and delay variation-bounded Steiner tree problem

The delay and delay variation-bounded Steiner tree problem is an important problem in real-time multimedia networks, and is known to be NP-complete. In this paper, we propose an efficient heuristic multicast routing algorithm based on simulated annealing named SADDVMA to construct the constrained Steiner tree. To avoid enlargement of search area and increase of computing time, the proposed heuristic algorithm uses a procedure called Paths-switching to construct neighbors in feasible region according to the relationship between delay and delay variation. We also give a method to dynamically reorganize the multicast tree in response to changes for the destinations. Simulations demonstrate that our algorithm is better in terms of tree cost as compared to the existing algorithms. Further, it performs excellent performance of delay and delay variation, rapid convergence and better real-time property.     

On Bandwidth-Efficient Overlay Multicast

In this paper, we propose a new multicast delivery mechanism for bandwidth-demanding applications in IP networks. Our mechanism, referred to as multiple-destination overlay multicast (MOM), combines the advantages of IP multicast and overlay multicast. We formulate the MOM routing problem as an optimization problem. We then design an algorithm based on Lagrangian relaxation on our formulation and propose a distributed protocol based on the algorithm. For network operators, MOM consumes less network bandwidth than both IP multicast and overlay multicast. For users, MOM uses less interface bandwidth than overlay multicast.     

The cost optimal solution of the multi-constrained multicast routing problem

In this paper, we define the cost optimal solution of the multi-constrained multicast routing problem. This problem consists in finding a multicast structure that spans a source node and a set of destinations with respect to a set of constraints, while minimizing a cost function. This optimization is particularly interesting for multicast network communications that require Quality of Service (QoS) guarantees. Finding such a structure that satisfies the set of constraints is an NP-hard problem. To solve the addressed routing problem, most of the proposed algorithms focus on multicast trees. In some cases, the optimal spanning structure (i.e. the optimal multicast route) is neither a tree nor a set of trees nor a set of optimal QoS paths. The main result of our study is the exact identification of this optimal solution. We demonstrate that the optimal connected partial spanning structure that solves the multi-constrained multicast routing problem always corresponds to a hierarchy, a recently proposed generalization of the tree concept. We define the directed partial minimum spanning hierarchies as optimal solutions for the multi-constrained multicast routing problem and analyze their relevant properties. To our knowledge, our paper is the first study that exactly describes the cost optimal solution of this NP-hard problem.