Energy efficient all-to-all broadcast in all-wireless networks

All-to-all broadcast is a communication pattern in which every node initiates a broadcast. In this paper, we investigate the problem of building a unique cast tree of minimum total energy, which we call Minimum Unique Cast (MUC) tree, to be used for all-to-all broadcast. The MUC tree is unoriented and unrooted. We study three known heuristics for the minimum-energy broadcast problem: the Broadcast Incremental Power (BIP) algorithm, the Wireless Multicast Advantage-conforming Minimum Spanning Tree (WMA-conforming MST) algorithm, and the Iterative Maximum-Branch Minimization (IMBM) algorithm. Experimental results conducted on various types of networks are reported. We show that neither of these methods is best overall for building all-to-all broadcast trees.     

On general results for all-to-all broadcast

All-to-all broadcast refers to the process by which every node broadcasts its certain piece of information to all other nodes in the system. In this paper, we develop all-to-all broadcast schemes by dealing with two classes of schemes. A prior scheme based on generation of minimal complete sets is first described, and then a new scheme based on propagation of experts is developed. The former always completes the broadcasting in the minimal number of steps and the latter is designed to minimize the number of messages. Performance of these two classes of schemes is comparatively analyzed. The all-to-all broadcast scheme desired can be derived by combining the advantages of these two classes of schemes     

Interleaved all-to-all reliable broadcast on meshes and hypercubes

All-to-all (ATA) reliable broadcast is the problem of reliably distributing information from every node to every other node in point-to-point interconnection networks. A good solution to this problem is essential for clock synchronization, distributed agreement, etc. We propose a novel solution in which the reliable broadcasts from individual nodes are interleaved in such a manner that no two packets contend for the same link at any given time-this type of method is particularly suited for systems which use virtual cut-through or wormhole routing for fast communication between nodes. Our solution, called the IHC Algorithm, can be used on a large class of regular interconnection networks including regular meshes and hypercubes. By adjusting a parameter η referred to as the interleaving distance, we can flexibly decrease the link utilization of the IHC algorithm (for normal traffic) at the expense of an increase in the time required for ATA reliable broadcast. We compare the IHC algorithm to several other possible virtual cut-through solutions and a store-and-forward solution. The IHC algorithm with the minimum value of η is shown to be optimal in minimizing the execution time of ATA reliable broadcast when used in a dedicated mode (with no other network traffic)     

Multi-hop all-to-all optical routings in Cartesian product networks

This paper considers the wavelength assignment problem for Cartesian product networks with multi-hops. An upper bound of the (uniform) wavelength index for Cartesian product networks with single-hop is established. This result leads to a consequence for the nth power of an arbitrary network with k-hops. In particular, if k=1, this bound partially generalizes the results of Pankaj [R.K. Pankaj, Architectures for linear lightwave networks, PhD thesis, Dept. of Electrical Engineering and Computer Science, MIT, Cambridge, MA, 1992], Bermond et al. [J.-C. Bermond, L. Gargano, S. Perennes, A.A. Rescigno, U. Vaccaro, Efficient collective communication in optical networks, Theoret. Comput. Sci. 233 (2000) 165-189] and Beauquier [B. Beauquier, All-to-all communication for some wavelength-routed all-optical networks, Networks 33 (1999) 179-187] for hypercubes and Hamming graphs. As an application, a tight upper bound for Hamming graph with k hops is established and a corresponding open problem is also proposed.     

Optimal NODUP all-to-all broadcast schemes in distributed computingsystems

Broadcast, referring to a process of information dissemination in a distributed system whereby a message originating from a certain node is sent to all other nodes in the system, is a very important issue in distributed computing. All-to-all broadcast means the process by which every node broadcasts its certain piece of information to all other nodes. In this paper, we first develop the optimal all-to-all broadcast scheme for the case of one-port communication, which means that each node can only send out one message in one communication step, and then, extend our results to the case of multi-port communication, i.e., k-port communication, meaning that each node can send out k messages in one communication step. We prove that the proposed schemes are optimal for the model considered in the sense that they not only require the minimal number of communication steps, but also incur the minimal number of messages     

A reservation protocol for broadcast WDM networks and stability analysis

We consider the problem of coordinating access to the various channels of a single-hop wavelength division multiplexing (WDM) network. We present a high performance reservation (HiPeR-ℓ) protocol specifically designed to overcome the potential inefficiencies of operating in environments with non-negligible processing, tuning, and propagation delays. HiPeR-ℓ differs from previous reservation protocols in that each control packet makes reservations for all data packets waiting in a node's queues, thus significantly reducing control overhead. Packets are scheduled for transmission using algorithms that can effectively mask the tuning times. HiPeR-ℓ also uses pipelining to mask processing times and propagation delays; parameter ℓ of the protocol is used to control the degree of pipelining. We use Markov chain theory to obtain a sufficient condition for the stability of the protocol. The stability condition provides insight into the factors affecting the operation of the protocol, such as the degree of load balancing across the various channels, and the quality of the scheduling algorithms. The analysis is fairly general, as it holds for MMBP-like arrival processes with any number of states, and for non-uniform destinations.     

Near-optimal all-to-all broadcast in multidimensional all-portmeshes and tori

All-to-all communication is one of the most dense collective communication patterns and occurs in many important applications in parallel and distributed computing. In this paper, we present a new all-to-all broadcast algorithm in multidimensional all-port mesh and torus networks. We propose a broadcast pattern which ensures a balanced traffic load in all dimensions in the network so that the all-to-all broadcast algorithm can achieve a very tight near-optimal transmission time. The algorithm also takes advantage of overlapping of message switching time and transmission time, and the total communication delay asymptotically matches the lower bound of all-to-all broadcast. Finally, the algorithm is conceptually simple and symmetrical for every message and every node so that it can be easily implemented in hardware and achieves the near-optimum in practice     

Adaptive scheduling for integrated traffic on WDM optical networks

One of the important issues in the design of future generation of high-speed networks is to provide differentiated service to different types of traffic with various time constraints. In this paper, we study the problem of providing real-time service to either hard or soft real-time messages and normal transmission service to variable-length messages without time constraints in WDM optical networks. We propose an adaptive scheduling algorithm for scheduling message transmissions in order to improve the network performance when both real-time and non real-time messages are transmitted in one topology. We have analyzed the complexity of the algorithm to show its feasibility. We have conducted extensive discrete-event simulations to evaluate the performance of the proposed algorithm. The study suggests that when scheduling message transmission in WDM networks differentiated services should be considered in order to meet time constraints of real-time messages while non real-time messages are being served so that the overall performance of the network could be improved.     

Dynamic survivable algorithm for meshed WDM optical networks

In this paper, we propose a novel heuristic survivable algorithm called dynamic path-shared protection (DPSP) to completely protect the double-link failures in meshed Wavelength-division-multiplexing (WDM) optical networks. In order to improve the algorithm performance, we focus on considering two key issues that are load balancing and resource-sharing degree when computing the working and backup paths. We also investigate the trap situations and present a solution method, because the trap situations may lead to high blocking probability (BP). Simulations results show that, DPSP can provide complete protection for the double-link failures; with respect to the previous work, DPSP not only can effectively avoid the trap situations but also is able to obtain higher resource utilization ratio and lower BP.     

Efficient fault-tolerant routing in multihop optical WDM networks

This paper addresses the problem of efficient routing in unreliable multihop optical networks supported by Wavelength Division Multiplexing (WDM). We first define a new cost model for routing in (optical) WDM networks that is more general than the existing models. Our model takes into consideration not only the cost of wavelength access and conversion but also the delay for queuing signals arriving at different input channels that share the same output channel at the same node. We then propose a set of efficient algorithms in a reliable WDM network on the new cost model for each of the three most important communication patterns-multiple point-to-point routing, multicast, and multiple multicast. Finally, we show how to obtain a set of efficient algorithms in an unreliable WDM network with up to f faulty optical channels and wavelength conversion gates. Our strategy is to first enhance the physical paths constructed by the algorithms for reliable networks to ensure success of fault-tolerant routing, and then to route among the enhanced paths to establish a set of fault-free physical routes to complete the corresponding routing request for each of the communication patterns     

Multicast protection scheme in survivable WDM optical networks

The protection design is a key issue in survivable wavelength division multiplexing (WDM) optical networks. Most researches focused on protecting unicast traffic against the failure of a single network component such as a link or a node. In this paper, we investigate the protection scheme for multicast traffic in meshed WDM optical networks under dual-link failure consideration, and propose a novel protection algorithm called shared segment protection with reprovisioning (SSPR). Through dynamically adjusting link-cost according to the current network state, SSPR establishes a primary light-tree and corresponding link-disjoint backup segments for each multicast connection request. A backup segment can efficiently share wavelength capacity of its working tree or the common resource of other backup segments. Capacity reprovisioning establishes new segments for the vulnerable connections after a link failure and tolerates following link failures. The simulation results show that SSPR not only can make good use of wavelength resources and protect multicast sessions against any single-link failure, but also can greatly improve the traffic restorability in the event of dual-link breakdown.     

WDM光网络动态虚拟拓扑重构算法

针对波分复用光纤网络上业务流量动态改变的问题,为了使光纤网络能支持更多的业务连接,需要对虚拟拓扑进行重构。基于链路最大负载和包平均跳步距离,利用混合线性规划公式对重构问题进行描述,在此基础上提出一个自适应拓扑重构算法,达到提高网络吞吐量的目的。仿真结果表明,该算法可以有效地改善网络性能。     

Optimal all-to-all personalized exchange in self-routablemultistage networks

All-to-all personalized exchange is one of the most dense collective communication patterns and occurs in many important applications in parallel computing. Previous all-to-all personalized exchange algorithms were mainly developed for hypercube and mesh/torus networks. Although the algorithms for a hypercube may achieve optimal time complexity, the network suffers from unbounded node degrees and thus has poor scalability in terms of I/O port limitation in a processor. On the other hand, a mesh/torus has a constant node degree and better scalability in this aspect, but the all-to-all personalized exchange algorithms have higher time complexity. In this paper, we propose an alternative approach to efficient all-to-all personalized exchange by considering another important type of networks, multistage networks, for parallel computing systems. We present a new all-to-all personalized exchange algorithm for a class of unique-path, self-routable multistage networks. We first develop a generic method for decomposing all-to-all personalized exchange patterns into some permutations which are realizable in these networks, and then present a new all-to-all personalized exchange algorithm based on this method. The newly proposed algorithm has O(n) time complexity for an n×n network, which is optimal for all-to-all personalized exchange. By taking advantage of fast switch setting of self-routable switches and the property of a single input/output port per processor in a multistage network, we believe that a multistage network could be a better choice for implementing all-to-all personalized exchange due to its shorter communication latency and better scalability     

A comparison of wavelength reservation protocols for WDM optical networks

In WDM optical networks, wavelength is the critical resource for efficient communication of traffic. Hence, suitable protocols are required to allocate and use the wavelengths efficiently. We have studied the wavelength reservation protocols of such networks, which are already developed and reported in literature. Following their historical development, we have outlined some generalized classification for them and provided comparison of their performances. Finally, on the basis of the previous works, we have discussed some future scopes, which may be explored for further improvement in performance of the protocols.     

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.     

Rerouting schemes for dynamic traffic grooming in optical WDM networks

Traffic grooming in optical WDM mesh networks is a two-layer routing problem to effectively pack low-rate connections onto high-rate lightpaths, which, in turn, are established on wavelength links. The objective of traffic grooming is to improve resource efficiency. However, resource contention between lightpaths and connections may result in inefficient resource usage or even the blocking of some connections. In this work, we employ a rerouting approach to alleviate resource inefficiency and improve the network throughput under a dynamic traffic model. We propose two rerouting schemes, rerouting at lightpath level (RRLP) and rerouting at connection level (RRCON) and a qualitative comparison is made between the two. We also propose two heuristic rerouting algorithms, namely the critical-wavelength-avoiding one-lightpath-limited (CWA-1L) rerouting algorithm and the critical-lightpath-avoiding one-connection-limited (CLA-1C) rerouting algorithm, which are based on the two rerouting schemes. Simulation results show that rerouting reduces the blocking probability of connections significantly.     

WDM 光网络双链路故障混合保护算法*

针对WDM光网络中的双链路故障,采用P-cycle与共享通路保护结合的方式来实现。其主要思路是：对给定的工作路径,在寻找一条与工作通路分离的保护通路的同时,再为工作通路上的每条链路寻找与保护通路部分分离的P-cycle。最后在三种不同的业务模型下进行了仿真,结果显示该算法能实现双链路故障的100%恢复,并且具有较低的阻塞率和资源冗余度。     

Routing and wavelength assignment for hypercube in array-based WDM optical networks

Hypercube is one of the most versatile and efficient communication patterns shared by a large number of computational problems. As the number of edges in hypercube grows logarithmically with the size of networks, the complexity of network topologies can be significantly reduced to realize hypercube in optical networks by taking advantage of the parallel transmission characteristic of optical fibers. In this paper, we study the routing and wavelength assignment for realizing hypercube on WDM optical networks including linear arrays and rings with the consideration of communication directions. Specifically, we analyze this problem for both bidirectional and unidirectional hypercubes. For each case, we identify a lower bound on the number of wavelengths required, and design the embedding scheme and wavelength assignment algorithm that uses a provably near-optimal number of wavelengths. In addition, we extend the results to meshes and tori. By our embedding schemes, many algorithms, originally designed based on hypercubes, can be applied to optical networks, and the wavelength requirements can be easily derived using our obtained results.     

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.     

Optimal all-to-all personalized exchange in a class of opticalmultistage networks

All-to-all personalized exchange is one of the most dense collective communication patterns and it occurs in many important parallel computing/networking applications. In this paper, we look into the issue of realizing an all-to-all personalized exchange in a class of optical multistage networks. Advances in electrooptic technologies have made optical communication a promising networking choice to meet the increasing demands for high channel bandwidth and low communication latency of high-performance computing/communication applications. Although optical multistage networks hold great promise and have demonstrated advantages over their electronic counterpart, they also hold their own challenges. Due to the unique properties of optics, crosstalk in optical switches should be avoided to make them work properly. In this paper, we provide a systematic scheme for realizing an all-to-all personalized exchange in a class of unique-path optical multistage networks crosstalk-free. The basic idea of realizing an all-to-all personalized exchange in such a multistage network is to transform it to multiple semipermutations and ensure that each of them can be realized crosstalk-free in a single pass. As can be seen, the all-to-all personalized exchange algorithm we propose has O(n) time complexity for n processors, which is optimal for an all-to-all personalized exchange. The optimal time complexity combined with the property of a single input/output port per processor suggests that a multistage network could be a better choice for implementing an all-to-all personalized exchange due to its shorter communication latency and better scalability