Nonblocking k-fold multicast networks

Multicast communication involves transmitting information from a single source to multiple destinations and is a requirement in high-performance networks. Current trends in networking applications indicate an increasing demand in future networks for multicast capability. Many multicast applications require not only multicast capability, but also predictable communication performance such as guaranteed multicast latency and bandwidth. In this paper, we present a design for a nonblocking k-fold multicast network, in which any destination node can be involved in up to k simultaneous multicast connections in a nonblocking manner. We also develop an efficient routing algorithm for the network. As can be seen, a k-fold multicast network has significantly lower network cost than that of k copies of ordinary 1-fold multicast networks and is a cost effective choice for supporting arbitrary multicast communication.     

Point-to-group blocking in the switching networks with unicast and multicast switching

In this paper, a new approximate effective availability method of the point-to-group blocking probability calculation in switching networks carrying a mixture of different multi-rate unicast and multicast traffic streams is presented. Until recently, such methods have only been proposed for the single-services switching networks. To the best of our knowledge, methods of blocking probability calculation for multi-service switching network with multicast connection have not yet been considered. In this paper, four algorithms of setting-up multicast connections in multi-service switching networks are considered and discussed. Special attention is paid to the methods for determining the effective availability parameter in the case of multicast connections. The results of the analytical calculations are compared with the data of the digital simulations of the switching networks with unicast and multicast connections.     

Protections for multicast session in WDM optical networks under reliability constraints

In this paper, we investigate protections of multicast session under reliability constraints in WDM optical networks, which is not referred in previous works. All of the papers about protection of multicast session discuss 100% reliability that may be distinct in different users’ requirement. At the beginning of the paper, we discuss the reliability of a tree. Then under reliability constraints, we propose three novel protection algorithms, which are Arc-Disjoint Tree with Different Reliability (ADT_DiR), Partial Tree Protection (PTP) and Choosing Segments Protection (CSP). ADT_DiR finds an arc-disjoint tree if the reliability of primary tree does not meet users’ requirement. PTP finds a small protection tree for some part of primary tree and also meets users’ requirement. CSP divides primary tree into segments first, and then protects some segments that are picked up by a strategy while satisfying users’ requirement. Compared with all protection schemes in other papers, which provide 100% reliability, ADT_DiR, PTP and CSP all decrease the resources needed by backup tree and reduce the failure probability of finding backup trees. The simulation results show that all the three protection schemes decrease the blocking ratio and reduce the protection resources consumed comparing to other protection schemes while meeting users’ requirement under dynamic traffics.     

Routing of multicast audio/video streams in reconfigurable WDM optical networks

Due to its low attenuation, fiber has become the medium of choice for point-to-point links. Using Wavelength-Division Multiplexing (WDM), many independent channels can be created in the same fiber. A network node equipped with a tunable optical transmitter can select any of these channels for sending data. An optical interconnection combines the signal from the various transmitters in the network, and makes it available to the optical receivers, which may also be tunable. By properly tuning transmitters and/or receivers, point-to-point links can be dynamically created and destroyed. Therefore, in a WDM network, the routing algorithm has an additional degree of freedom compared to traditional networks: it can modify the netowrk topology to create the routes. In this paper, we consider the problem of routing multicast audio/video streams in WDM networks and propose heuristic algorithms to solve it. The performance of these heuristics is evaluated in a number of scenarios, with a realistic traffic model, and from the evaluation we derive guidelines for usage of the proposed algorithms.This work was supported in part by NASA under grant NAG2-842, by the National Science Foundation under grant NCR-9016032 and by Pacific Bell. Ciro Noronha was supported by a graduate scholarship from FAPESP from Sept/89 to Aug/93 under grant 89/1658.     

Algorithms for burst rescheduling in WDM optical burst switching networks

Wavelength division multiplexing (WDM) is a promising technology for realizing terabit networks. Optical burst switching (OBS) is a way to efficiently support bursty traffic on WDM-based optical Internet networks. In OBS networks, the control (header) and payload (data) components of a burst are sent separately with a time gap. The control packet first traverses the burst switching nodes and reserves suitable wavelengths on the links for the corresponding data burst by using a scheduling algorithm. Our work is motivated from the observation that the existing scheduling algorithms either have low computational complexity or high performance in terms of burst dropping probability, but not both simultaneously. Since the arrival of bursts is dynamic, it is highly desirable that the scheduling is done as quickly as possible. We develop scheduling algorithms which integrate the merits of both low computational complexity and high burst dropping performance. The key idea is to reschedule an existing burst by assigning a new wavelength to it keeping the burst arrival and leaving time unchanged in order to accommodate the new burst. We propose computationally simple rescheduling algorithms called on-demand burst rescheduling and aggressive burst rescheduling. The effectiveness of the proposed algorithms and the signaling overhead are studied through simulation experiments.     

c-HyLabs混合光交换网络上的多播机制研究

在WDM网络中有两种全光多播方式,一种是OCS（光电路交换）网络中基于光树的多播,另一种就是在OBS（光突发分组交换）网络中基于突发分组的多播。这两种方式都有各自的优缺点。在分析这两种交换技术优缺点的同时,提出了一种采用混合交换技术的新型光交换网络（c-HyLabs）,并提出了在此网络上实现光多播的机制。通过OPNET的仿真表明,该混合光交换网络在相同条件下其延时及丢包率等性能均优于OBS网络多播。     

Genetic algorithm for finding minimal cost light-forest of multicast routing on WDM networks

Wavelength division multiplexing (WDM) is an important technique to make use of the large amount of bandwidth in optical fibers to meet the bandwidth requirements of applications. Multicast is the transmission of information from one source to multiple destinations simultaneously. Given a multicast request in a WDM network, the goal is to find a set of light-trees, the assigned wavelengths of light-trees, and construct a light-forest. In this paper, the Minimal cost multicast routing problem (MCMRP) on WDM networks with Tap-and-continue nodes is defined and studied. A new cost model which consists of thewavelength usage and communication cost is defined. The objective is to minimize the sum of the cost of used wavelengths and the communication cost of the light-forest. Specifically, the formulation for the WDM multicast routing problem is given. Because the MCMRP is NP-hard, two genetic algorithms (GAs) are proposed to solve this problem. In the proposed GAs, a path-oriented encoding chromosome is used to represent the routing paths. These routing paths are used to construct source-based light-forests to represent a feasible solution to the multicast request. Moreover, to speed up the convergence of GAs, a Farthest-first greedy heuristic algorithm is proposed and used to generate one of the initial chromosomes. Simulation results demonstrate that the proposed GAs can run efficiently.     

On-line multicast routing with QoS constraints in WDM networks with no wavelength converters

The rapid growth of multicast applications initiated the need to realise multicasting in Wavelength Division Multiplexing (WDM) networks in an efficient and cost-effective way. However, most of the applications need to support dynamic multicast sessions wherein the membership of the multicast group changes with time as nodes join or leave the session dynamically. In addition, with the advancements in the multimedia and other real-time group applications, the construction of multicast trees satisfying Quality of Service (QoS) requirements of the member nodes is becoming a problem of prime importance. In this paper, we deal with on-line QoS multicast routing in WDM networks. As members leave the sessions, it will be mandatory to rearrange the trees in order to save costs, at the same time accounting for the disruption caused to the ongoing transmissions because of the rearrangement. We try to effectively decrease the disruption by considering only certain portions of the multicast tree and limiting the rearrangement to only those portions. A region’s usefulness to the overall tree is judged by a novel concept of Cost-to-Service Ratio (CSR) and a region is selected for rearrangement based on its CSR value. Extensive simulation results reveal that rearrangements based on CSR can reduce the disruption to the member nodes by 20–85% compared to rearrangements based on the best known metric (Quality Factor) in the literature, for the same cost performance. We also demonstrate the cost-effectiveness of the trees generated by our on-line algorithm compared to that of static algorithm.     

Scheduling algorithms for multicast traffic in TDM/WDM networks with arbitrary tuning latencies

We consider all-optical Time Division Multiplexing (TDM)/Wavelength Division Multiplexing (WDM) broadcast and select networks with slotted operation. Each network access node is equipped with one fixed transmitter and one tunable receiver; tuning times are not negligible with respect to the fixed size slot time. We discuss efficient scheduling algorithms to assign TDM/WDM slots to multicast traffic in such networks. The problem is shown to be NP-hard; thus, heuristic algorithms based on the Tabu Search meta-heuristic are proposed, and their performance are assessed using randomly created request matrices based on two types of multicast traffic patterns. We show that significant advantages can be obtained by using these novel algorithms with respect to simpler greedy algorithms, even when restricting CPU times to realistic values to make the algorithms of practical use.     

A multi-granularity evolution based Quantum Genetic Algorithm for QoS multicast routing problem in WDM networks

QoS multicast routing problem in WDM networks is investigated, and an improved algorithm Multi-granularity Evolution based Quantum Genetic Algorithm (MEQGA) is proposed to address it. Based on Quantum Genetic Algorithm (QGA) with quantum rotation gate strategy, MEQGA introduces multi-granularity evolution mechanism, which allows different chromosomes of one generation to have different rotation angle step values to update. In term of this mechanism, MEQGA can significantly improve its capability of exploration and exploitation, since its optimization performance does not over-depend on the single rotation angle step scheme shared by all chromosomes any longer. MEQGA also presents an adaptive quantum mutation operation which is able to avoid local search efficiently. A repair method is applied to eliminate illegal graphs as many as possible hence more excellent solutions will appear in each evolutionary generation. Simulation results show that, for the QoS multicast routing problem, MEQGA outperforms other heuristic algorithms and is characterized by robustness, high success ratio, fast convergence and excellent capability on global searching.     

Modular multicast ATM switching architecture

A modular multicast packet switching architecture is proposed for the B-ISDN/ATM. In this switching architecture, we use the abilities of a broadcast bus suitable for multicasting services. Instead of using the concatenation of a copying network and a routing network, we use the same switching network to perform both copying and routing of multicast packets. This multicast switch architecture treats unicast and multicast packets in the same way; the delay time for these two kinds of packets has the same characteristics for the affective load in the switching. Through the modularity of this switching architecture, it is easy to dimension the switching system. We also include a mathematical analysis of this architecture.     

A simulation study of optical burst switching and access protocols for WDM ring networks

We consider a wavelength division multiplexing metro ring architecture with optical burst switching. The ring consists of N nodes, and each node owns a home wavelength on which it transmits its bursts. The ring operates under the fixed transmitter tunable receiver scheme. Control information is transmitted on a separate control channel. Five different burst switching access protocols are proposed, and their performance and fairness is evaluated by simulation.     

Link scheduling state information based offset management for fairness improvement in WDM optical burst switching networks

In wavelength division multiplexed (WDM)-based optical burst switching (OBS) networks, bursts that traverse longer paths are more likely to be dropped compared to bursts that traverse shorter paths resulting in a fairness problem. Fairness here refers to having, for all ingress–egress node pairs in a network, a burst to have equal likelihood to get through independent of the hop length involved. In this paper, we develop a link scheduling state based fairness improvement method which can be used in a classless as well as a multi-class environment. The basic idea is to collect link scheduling state information and use it to determine the offset times for routes with different hop lengths. By using the online link state information, this method periodically computes and adapts the offset times needed, thus inherently accounting for the traffic loading patterns and network topological connectivity. It also ensures that the delay experienced by a burst is low and shorter-hop bursts are not over-penalized while improving the performance of longer-hop bursts. The effectiveness of the proposed method is evaluated through simulation experiments.     

Pseudo-cycle-based multicast routing in wormhole-routed networks

This paper addresses the problem of fault-tolerant multicast routing in wormholerouted multicomputers.A new pseudo-cycle-based routing method is presented for constructing deadlock-free multicast routing algorithms.With at most two virtual channels this technique can be applied to any connected networks with arbitrary topologies.Simulation results show that this technique results in negligible performance degradation even in the presence of a large number of faulty nodes.     

IP multicast routing through ATM networks

The purpose of this paper is to have a closer look at the ‘core’ technology providing interworking between connectionless TCP/IP internetworks and switched ATM networks. The scope of the paper is IP multicast, while the main focus is on the network side of multicast, more precisely, on layers three and two of Internet architecture dealing with IP multicast routing. The paper analyses both practically available solutions and those being currently under discussion in IETF as Internet drafts. As a background of this comparison, the possible convergence of IP and ATM multicast service models is discussed. Major conclusions, based on simulation studies and scalability analysis are: (i) the high mapping overhead requires a separate address resolution service for unicast and multicast addresses; and (ii) efficient convergence has to make obsolete classical IP over ATM (M. Laubach, Classical IP and ARP over ATM, Network Working Group, Request for Comments: 1577, Category: Standards Track, January, 1994 [1]) in order to permit ‘cut-through’ within the ATM domain.     

SMDS multicast support in ATM networks

In this paper we show that an ATM network equipped with Connectionless Servers (which are interconnected by a CLS overlay network) can adequately support SMDS multicasting as well as other key SMDS features. We argue that multicast traffic is most efficiently transmitted on multicast trees, and propose a scheme for the computation and maintenance of such trees exploiting the underlying routing procedure. We then review a number of CLS network design options and variables, namely, encapsulation, on-the-fly transmission, packet dropping and virtual topology. We evaluate the impact of these choices on the multicast service.     

Unicast-based multicast communication in wormhole-routed networks

Multicast communication, in which the same message is delivered from a source node to an arbitrary number of destination nodes, is being increasingly demanded in parallel computing. System supported multicast services can potentially offer improved performance, increased functionality, and simplified programming, and may in turn be used to support various higher-level operations for data movement and global process control. This paper presents efficient algorithms to implement multicast communication in wormhole-routed direct networks, in the absence of hardware multicast support, by exploiting the properties of the switching technology. Minimum-time multicast algorithms are presented for n-dimensional meshes and hypercubes that use deterministic, dimension-ordered routing of unicast messages. Both algorithms can deliver a multicast message to m-1 destinations in [log ₂ m] message passing steps, while avoiding contention among the constituent unicast messages. Performance results of implementations on a 64-node nCUBE-2 hypercube and a 168-node Symult 2010 2-D mesh are given     

基于分配格理论的大规模线速组播交换系统

采用Altera公司的StratixIV系列FPGA芯片为平台,根据代数分配格理论,构造适合组播的排序结构;结合已建立的多路径自路由结构;最终构造出基于代数分配格的线速组播交换结构。同时,研究此结构应用于大规模组播交换的方法,并设计支持该结构的自路由组播线速扇出复制过程的带内信令机制和控制机制。     

Cross-layer optimization for wireless multihop multicast networks

Cyber-Physical System (CPS) is envisioned to tightly integrate the cyber-world of computation, communication, and control with the physical world. CPS is typically designed as a networked system of interacting sensors, actuators, and embedded computing devices to monitor and control the physical world. Thus, one of the essential building blocks of such a system is a highly efficient networking infrastructure. In this paper, we aims to develop an efficient wireless networking technology which can be utilized in CPS. More specifically, we develop a cross-layer optimization model based on the Network Utility Maximization (NUM) framework and its distributed solution for wireless multihop multicast networks exploiting multi-user diversity. It is known that the capacity of a wireless network can be increased by exploiting different channel conditions at different users, i.e., multi-user diversity; however, it is yet to be determined how much performance gain can be achieved by exploiting multi-user diversity in wireless multihop multicast networks. To address this problem, we extend the NUM framework and derive a new optimization problem including the benefits of multi-user diversity for multicasting scenarios in wireless multihop networks under a probabilistic media access control (MAC). In our problem, multi-user diversity is achieved via opportunistic scheduling. Then, we propose a distributed approximation algorithm for the problem. Our numerical results confirm that the benefit of multi-user diversity is prominent in a wireless multihop network with multicast flows.