基于约束路由的绿色虚拟拓扑设计算法

摘 要：针对Internet核心网日益严重的能耗问题,建立了绿色虚拟拓扑设计(GVTD)问题的形式化模型,通过业务汇聚、按需配置网络资源、动态虚拟拓扑设计和多粒度睡眠机制降低网络能耗。提出了一种基于约束路由的启发式算法——CBR-GVTD算法,利用单跳路由和多跳路由相结合的方法构建网络虚拟拓扑,并通过基于约束的路由实现网络功耗与路由性能的折衷。模拟结果表明,CBR-GVTD算法可在接口平均利用率为80%~90%和最大路由跳数不超过5的条件下,最多可降低62%~90%的网络功耗     

Towards energy efficiency in virtual topology design of elastic optical networks

Elastic optical networks offer a reliable platform for achieving energy efficiency by supporting extensive optical grooming of variable‐rate data traffic along with the traditional electrical data aggregation methods. The procedure of routing and spectrum allocation in a topology of nodes has explicit effect to the amount of consumed power. A new energy‐efficient method for designing the virtual topology in IP‐over‐elastic networks is introduced and evaluated. It is concluded that it consumes less power under different elastic transponder types, it designs the virtual topology using fewer transponders, and finally, there is a slight increase in the number of end‐to‐end lightpath hops. The proposed method is characterized by high performance and low lightpath establishment complexity. Therefore, it is suitable for a broad range of network configurations and transponder types.     

Efficient distributed address assignment algorithm based on topology maintenance in ZigBee networks

Adopting the borrowed address algorithm can decrease the orphan nodes in ZigBee networks that use distributed address assignment mechanism （DAAM）. The existing borrowed address algorithms can increase the success rate of address assignment, but they have defects such as greater cost of overhead and time in founding network caused by breaking topology. To solve such problems, we propose an more efficient distributed borrowed address assignment algorithm based on topology maintenance （A2BTM） that has a topology maintenance function. It borrows address firstly from the offspring nodes in the same branch for the orphan nodes and replies distributed the request of the borrowed address message immediately, to maintain the network topology and decrease the overhead and time spent on the mechanism of borrowed address. Theoretical and simulation analyses manifest that AZBTM algorithm outperforms DAAM and its improved algorithms in terms of the overhead and time spent in founding network, on the premise of keeping a higher success rate of address assignment. Furthermore, A2BTM can lessen the influence from detour phenomenon efficiently.     

Physical topology design for all-optical networks

When designing an all-optical network, the designers face a choice of laying down more fibers or increasing the number of wavelengths. Although either choice could be used to support new connections, one increases the link cost and the other increases the node (wavelength equipments) cost. The tradeoffs between link and node cost are not well understood. Using the efficient physical topology design algorithm that we propose, we study this tradeoff. We use the asymptotic growth rate of the provisioned capacity as a metric to compare various design alternatives. A higher asymptotic growth rate translates directly into a higher deployment cost for large networks. Our study shows that taking fiber length into consideration can lead to lower capacity requirement. We also find that a sufficiently large fiber-to-node ratio is necessary in order to minimize the asymptotic growth in the provisioned capacity, increase capacity utilization and minimize the need for wavelength conversion. We study a real network and find that its fiber-to-node ratio is too low. As a result, large provisioned capacity is required and less than 55% of the capacity is usable. By increasing the ratio, we can reduce the provisioned capacity and achieve close to 80% utilization.     

A fast topology maintenance algorithm for high-bandwidth networks

A fast time-driven algorithm for topology maintenance in high-speed networks is presented. The algorithm uses only four time units for each broadcast by each computer. The best previous algorithm required O(log m) time units for each broadcast by each computer, where m is the number of currently operational computers in the network. In addition to its speed, the presented algorithm makes several significant contributions. I. Cidon et al. (1988) have shown that Ω(log m) time units are necessary for time-driven topology maintenance algorithms of high-speed networks that do not allow a packet to traverse the same edge in both directions. The proposed algorithm shows that this lower bound does not hold for networks that do allow a packet to traverse the same edge in both directions. The O(log m) algorithm assumed that it takes each computer at most one time unit to simultaneously broadcast messages to all neighbors of the computer. In contrast, a node in the proposed algorithm can send at most, one message per time unit. As in the O(log m) algorithm, the algorithm requires O (D) broadcasts per node before all nodes know the correct topology of the network, where D is the diameter of the currently operational portion of the network     

IP over WDM网络中一种新型虚拓扑构造算法

对IP over WDM的虚拓扑设计算法进行了研究，选择网络整体流量的均衡性作为优化目标，提出了一种新型的虚拓扑构造算法。在算法中，选择负载分布方差作为评价流量均衡性的指标，并给出其定义和计算方法。主要针对拥塞概率性能，在光层和IP层将提出的新型虚拓扑构造算法与其他算法进行比较。在光层的算法比较部分，选择负载均衡启发式路由算法（RLBH，routing with load balancing heuristics）与提出的算法进行比较；在IP层的算法比较部分，选择固定路径最小拥塞路由算法（FPLC，fixed-path least-congestion）与提出的算法进行比较，并对比较结果进行了讨论。比较结果显示在拥塞概率性能方面，提出的新型虚拓扑构造算法优于RLBH算法和FPLC算法。     

Joint scheduling and virtual topology design for sliding periodic traffic

Two possible approaches can be considered for solving the virtual topology design problem for periodic (multi-hour) traffic demands. The first approach attempts to design a static topology that can accommodate all the traffic variations over time. The second option is to determine an appropriate series of virtual topologies to accommodate the different traffic loads at different times. This can lead to some savings in terms of the number of transceivers needed, but it requires the use of costly reconfigurable switching equipment. So, strategies for stable virtual topology design have received considerable attention in recent years. However, all the works reported in the literature so far, focus on the fixed window scheduled traffic model, where the start and end times of the demands are known in advance. In this paper, we propose a new integrated approach using the more general sliding window model, for jointly scheduling the demands in time and designing a logical topology that can accommodate all the scheduled demands. The goal is to a find a suitable static topology that can handle fluctuations in the offered sub-wavelength traffic load, without requiring the use of reconfigurable optical switching equipment. We first present a comprehensive integer linear program (ILP) formulation for designing a cost-efficient, stable logical topology for time-varying demands, and then propose an integrated heuristic algorithm capable of handling larger networks. Simulation results demonstrate the advantages of the proposed approaches, not only compared to holding time unaware models, but also over the traditional fixed window model.     

Distributed virtual network topology control mechanism in GMPLS-based multiregion networks

This paper proposes a distributed virtual network topology (VNT) reconfiguration method for Internet Protocol over a wavelength-division-multiplexing network under dynamic traffic demand. We have developed a simple heuristic algorithm for calculating the VNT for distributed control. A generalized multiprotocol label switching (GMPLS)-based routing protocol has been developed. The VNT is quickly reconfigured by setting up and/or tearing down lightpaths using a GMPLS signaling protocol. Traffic demand is measured at the ingress node and advertised by the extended GMPLS routing protocol. Performance of the proposed method is investigated using variable traffic model.     

MST-based clustering topology control algorithm for wireless sensor networks

In this paper, we propose a novel clustering topology control algorithm named Minimum Spanning Tree (MST)-based Clustering Topology Control (MCTC) for Wireless Sensor Networks (WSNs), which uses a hybrid approach to adjust sensor nodes’ transmission power in two-tiered hierarchical WSNs. MCTC algorithm employs a one-hop Maximum Energy &; Minimum Distance (MEMD) clustering algorithm to decide clustering status. Each cluster exchanges information between its own Cluster Members (CMs) locally and then deliveries information to the Cluster Head (CH). Moreover, CHs exchange information between CH and CH and afterwards transmits aggregated information to the base station finally. The intra-cluster topology control scheme uses MST to decide CMs’ transmission radius, similarly, the inter-cluster topology control scheme applies MST to decide CHs’ transmission radius. Since the intra-cluster topology control is a full distributed approach and the inter-cluster topology control is a pure centralized approach performed by the base station, therefore, MCTC algorithm belongs to one kind of hybrid clustering topology control algorithms and can obtain scalability topology and strong connectivity guarantees simultaneously. As a result, the network topology will be reduced by MCTC algorithm so that network energy efficiency will be improved. The simulation results verify that MCTC outperforms traditional topology control schemes such as LMST, DRNG and MEMD at the aspects of average node’s degree, average node’s power radius and network lifetime, respectively.     

Logical topology design for linear and ring optical networks

The design of logical topologies in wavelength-routing multihop optical networks is a well-studied problem. We consider logical topology (LT) design over the popular ring and linear topologies. Our objective is the minimization of the electronic processing delay for the worst case traffic flow. For uniform traffic between nodes, this delay minimization corresponds to minimizing the number of hops on a shortest path between the farthest two nodes in the logical topology (the diameter of the logical topology). The simple structure of the physical topologies enables us to present a rigorous analysis of the problem. We present lower bounds for the achievable diameter wherever possible and propose practical logical topology design algorithms and corresponding upper bounds. We also present an application of the LT designs in the linear topology to the survivability of ring networks     

WDM网络拓扑重构的均衡算法研究

针对WDM光网络中逻辑拓扑的重构迁移问题,提出一种均衡算法,以单条光通道为最小的计算单元,每次选择建立对当前的拓扑性能增益较多而中断的网络资源较少的光通道.仿真结果说明这样的做法有效降低了拓扑重构对网络的影响.     

Traffic-based topology control algorithm for energy savings in multi-hop wireless networks

This paper presents a traffic-based topology control algorithm for multi-hop wireless networks, in order to optimize the global energy consumption while maximizing the aggregate throughput. Contrary to major related works, we do not consider that reducing transmission powers implies reducing interferences and that the traffic is uniformly distributed among the links. Thus, we propose to dynamically calculate the transmission power of nodes depending on the traffic. First, we redefine the N-hop interference model for varying transmission powers. Then, we define a function giving the minimum interference according to the transmission powers. We propose several algorithms minimizing this function: global optimization, local optimization, and distributed optimization for a limited computation cost. Our first algorithm is used as a reference for limited cases. We show by simulation that our heuristics are relevant compared to existing works.     

Survivable virtual topology mapping in IP-over-WDM networks using differential evolution optimization

In IP-over-wavelength division multiplexing networks, a virtual topology is placed over the physical topology of the optical network. Given that a simple link failure or a node failure on the physical topology can cause a significant loss of information, an important challenge is to make the routing of the virtual topology on to the physical topology survivable. This problem is known as survivable virtual topology mapping (SVTM) and is known to be an NP-complete problem. So far, this problem has been optimally solved for small instances by the application of integer linear programming and has been sub-optimally solved for more realistic instances by heuristic strategies such as ant colony optimization and genetic algorithms. In this paper, we introduce the application of differential evolution (DE) to solve the SVTM problem and enhancements based on DE are proposed as well. Three algorithms based on DE are developed. The enhanced variants have better convergence rate, get better quality of solutions and require few control parameters. We present the impact of these parameters on the system’s performance improvement. Algorithms are evaluated in different test bench optical networks, as NSFnet and USA, demonstrating that the enhanced DE algorithm overcomes the other two, for small instances. The three algorithms reach a 100  survivable mapping for small instances. The three algorithms also find positive survivable mappings and reduce the network wavelength links. Results show the effectiveness and efficiency of the proposed algorithms.     

Logical topology design for dynamic traffic grooming in WDM optical networks

Traffic grooming in optical networks refers to consolidation of subwavelength client connections onto lightpaths. Depending on whether client connections are given in advance or randomly arrive/depart, traffic grooming is classified as static and dynamic. Dynamic traffic grooming has been traditionally performed through establishing/releasing lightpaths online. In this paper, the authors propose an alternate approach to design a static logical topology a priori and then route randomly arriving client connections on it to avoid frequent lightpath setup/teardown. Two problems are considered: 1) minimize resource usage constrained by traffic blocking requirements and 2) maximize performance constrained by given resources. These are formulated as integer linear-programming (ILP) problems. The numerical results show that the resource usage dramatically decreases when the blocking requirement is relaxed, and the grooming performance slowly increases when given more resources. In addition, the number of ports at client nodes has more profound impact on traffic grooming than the number of wavelengths.     

New algorithm for hub-and-spoke topological virtual networks embedding problem

The virtual network embedding/mapping problem is a core issue of the network virtualization.It's mainly concerned with how to map virtual network requests to the substrate network efficiently.Previous ...     

Efficient synthesis algorithm for low-power ASIC design

The authors propose an efficient synthesis algorithm for the synthesis of RT-level hardware with low power consumption. The proposed algorithm minimises the overall power consumption of generated datapath by reducing spurious operations. Experimental results for several benchmark circuits under various synthesis constraints show the efficiency of the proposed algorithm     

Efficient algorithm for logic design using multiplexers

An algorithmic procedure has been developed for the realisation of any Boolean function F(n) of n variables with a single multiplexer of minimum size. This procedure gives the choice of control variables to be used for the realisation of the function. The algorithm is iterative in nature and very suitable for machine implementation     

Efficient topology construction and routing for IEEE 802.15.4m-based smart grid networks

IEEE 802.15.4m TVWS Multi-Channel Tree PAN (TMCTP) standard that uses the vacant TV frequency of a region is the key to provide a flexible, scalable and cost-effective AMI smart grid networks. However, the performance of the IEEE 802.15.4m based AMI network can suffer from network interruption, varying transmission reliability and energy consumption problems due to the excessive number of channels and periodic channel scanning. To resolve these issues, we presented an enhanced IEEE 802.15.4m TMCTP called TVWS Orphan channel scanning with Multi-Channel Tree PAN Routing (TOMTPR). The proposed TOMTPR framework includes pilot-channel based Multi-Channel beaconing and interleaving-based TVWS orphan channel scanning. Furthermore, a capacity-aware routing tree is constructed during the neighbor discovery procedure. The proposed protocol suite is designed to provide compatibility with the IEEE 802.15.4 family standards with lower architecture complexity. The simulation results in presence of realistic AMI traffic and AMI network model show that TOMTPR can not only satisfy delay requirements of the AMI traffic, but also outperforms IEEE 802.15.4m TMCTP with IEEE 802.15.5 layer 2 mesh routing in terms of topology construction delay, end-to-end transmission reliability, and energy efficiency.     

An architecture for mobile radio networks with dynamically changing topology using virtual subnets

An architecture adaptabie to dynamic topology changes in multi-hop mobile radio networks is described. The architecture partitions a mobile network into logically independent subnetworks. Network nodes are members of physical and virtual subnets and may change their affiliation with these subnets due to their mobility. Each node is allocated an address based on its current subnet affiliation. We observe-especially in large networks with random topology-that partitioning of the network may result in significantly more balanced load than in one large multi-hop network, an attribute that can significantly improve the network's performance. The architecture is highly fault-tolerant, has a relatively simple location updating and tracking scheme, and by virtue of its load balancing feature, typically achieves a network with relatively high throughput and low delay. The addressing method, logical topology, mobility management and routing procedure are described, and network performance is evaluated.     

Efficient heuristics for the design of ring networks

In telecommunications, the Ring Design Problem (RDP) lies at the heart ofmetropolitan area network design. We propose an integer programming formulation for the RDP, as well as several ring construction and post-optimization heuristics. These heuristics are tested and compared on a series of test problems.