Multilayer traffic engineering for energy efficiency

Automatically switched multilayer IP-over-optical networks offer extensive flexibility in adapting the network to offered IP/MPLS traffic. Multilayer traffic engineering (MLTE) takes advantage of this through online IP logical topology reconfiguration in addition to the more traditional rerouting. The main goal of MLTE is to optimize toward resource usage, bandwidth throughput and QoS performance. However, energy efficiency of ICT infrastructure and the network in particular more recently have become an important aspect as well. In this article, we will look how MLTE helps in improving network energy efficiency. For this we will explain how optimization toward power requirement relates to the traditional resource usage minimization objective, and how power requirement in the network can be modeled for the MLTE algorithm. We will discuss two cases where the merit of MLTE for energy efficiency is discussed. Firstly, we will examine the interaction of MLTE with hardware-based energy efficiency optimization techniques; for this we look at scaling back power requirements through the use of better chip technology, but also decreasing idle-power requirement only, using improved chip architecture. Secondly, as MLTE allows for fast responses to changing traffic, we will see how link switch-off during off-peak hours offers a straightforward option to reduce energy needs.     

Multilayer traffic engineering for GMPLS-enabled networks

In recent years, significant work has been completed on traffic engineering enhancements to the generalized multiprotocol label switching protocol suite (E. Mannie Oct 2004) (D. Katz et al., Sept. 2003) (K. Kompella et al., Oct 2003). As a next step, reproducing the current trend of switching layers' integration happening in the data plane, network control is foreseen to go beyond the traditional per layer approach and tend toward an integrated model (K. Shimoto et al., Oct 2004) (E. Dotaro et al., Dec. 2004). In these multilayer environments, a single GMPLS control plane drives various distinct switching layers at the same time and as a coherent whole, taking benefit from the "common" property of GMPLS. Beyond this application of supporting network control across different technologies, in this article we catalog the unified traffic engineering paradigms, discuss their applicability, and present their enforcement techniques. Furthermore, we show that the common GMPLS concept has the advantage of low operational complexity, and enables unified TE capabilities such as efficient network resource usage and rapid service provisioning.     

流量工程中静态路由算法的研究

该文提出了一种应用于流量工程环境中的静态路由算法。考虑当前的网络资源情况,分优先级别在网络中计算并配置标记交换路径(Label Switched Path,LSP),当某一优先级有多条 LSP需要并行配置时,利用遗传算法搜索最优或较优的配置方案,使得网络的链路带宽使用率低于管理员定义的某个限定值,达到合理分布资源的目的。此外,提出了一种改进的 Dijkstra 算法计算 LSP的最短路径。     

On efficient traffic engineering with DV-based routing protocols in DiffServ-aware IP networks

In this paper, an approach to efficient traffic engineering in the DiffServ-aware network environment is proposed. We focus to distance vector-based routing protocols, considering both modifications of routing protocols needed to support path differentiation and traffic engineering methods relied on adjusting multiple per-link costs to particular network conditions. Further, a method for determining link cost of particular traffic class, as a unique generic function of the single generalized performance metric has been proposed. In order to achieve efficient traffic engineering, possible approximations of generic cost function and mappings of generalized to particular metrics have been proposed. Finally, prerequisites for implementing proposed approach have been discussed in the context of different administrative policies and time scales of their application.     

MTRA: An on-line hose-model VPN provisioning algorithm

Virtual private networks (VPNs) provide customers with a secure and manageable communication environment. The allocation of bandwidth for VPNs to meet the requirements specified by customers is now one of the most important research issues in the field of traffic engineering. A VPN resource-provisioning model called hose-model was developed to provide customers with a flexible and convenient way to specify the bandwidth requirements of a VPN. Several hose-model VPN provisioning algorithms have already been proposed. They focus on the bandwidth efficiency issue in the case of establishing a single hose-mode VPN. However, these algorithms cannot achieve a satisfactory rejection ratio when: (1) the residual bandwidths on links of the network backbone are finite and (2) multiple VPN setup requests are handled on-line. In this paper, we propose a new hose-model VPN provisioning algorithm called MTRA to address the issue. MTRA can process multiple VPN setup requests rapidly and reduce the rejection ratio effectively. Theoretical upper bounds of rejection ratios achieved by several VPN provisioning algorithms are also derived. The experiments verify that MTRA performs better in regards to the rejection ratio than other provisioning algorithms.     

A multiservice traffic allocation model for LEO satellite communication networks

Modern telecommunication networks are characterized by a heterogeneous mix of traffic classes, ranging from traditional telephone calls to video and data services. Therefore, there is a need to solve the traffic allocation problem with different quality-of-service (QoS) requirements, wherein each traffic demand is fulfilled. This paper investigates the possibility of allocating loaded traffic in a low earth orbital (LEO) satellite network by considering multiservice traffic. Both Poisson and Markov models are used for the incoming traffic, which includes multiservice requirements. By introducing a privilege parameter, a quantum of bandwidth can be reserved for high priority traffic and a better QoS can be given for this traffic. The algorithm performs well for both traffic patterns tested. Simulation results are presented.     

多层前馈神经网络快速学习算法的实现

本文评述优化学习率BP(Back Propagation)算法,给出应用研究中几种常用网络结构的优化学习率的计算公式,讨论与算法实现相关的一些问题.模拟实验结果进一步揭示算法的快速性质.     

Performance analysis of an improved soft preemptive scheme for unevenly distributed traffic in optical wavelength-division multiplexing networks

In optical wavelength-division multiplexing (WDM) networks, traffic can be unevenly distributed across the network causing inefficient utilization of resources. To solve this problem, an improved soft preemptive (SP) scheme is proposed by considering dynamic resource distribution to deal with the uneven network utilization. A novel unevenly distributed traffic model in cross-time-zone networks is also presented to evaluate the efficiency of the new scheme. Compared with other schemes such as normal shortest path first (SPF) routing and wavelength conversion (WC), the new proposed scheme results demonstrate significantly better performance with respect to the network utilization and overall network blocking probability.

Virtual topology reconfiguration on optical WDM networks considering traffic grooming

This paper investigates the virtual topology reconfiguration (VTR) problem of optical WDM networks by taking the traffic grooming factor into consideration. Firstly, by applying a common “divide and conquer” approach, the problem is categorized and handled as two independent sub-problems, triggering policy and the proper algorithm. Secondly, the VTR problem considering traffic grooming is formulated with new variables and constraints by a mixed-integer linear program (MILP). In order to handle the tradeoff between the advantages and disadvantages of VTR, both network resource utilization and network disruption are examined and quantified in terms of measurable parameters. A new multi-objective VTR algorithm called integrated reconfiguration (IR) algorithm is proposed to provide better overall VTR performance. Different from previous studies this newly proposed VTR algorithm combines three main factors (traffic load, traffic grooming ratio and route length of lightpaths) into one single objective and considers them all when reconfiguring. The results of simulations indicate that proposed VTR policy, periodic VTR triggering policy with IR algorithm, achieves performance improvements for overall VTR performance.     

Is multilayer networking feasible?

IP traffic has been growing every year, bringing the need for deploying an IP backbone interconnected by links provided by the transport network. Thus, network operators have had traditionally divided their core network in two, the IP network and the transport network. Network planning and engineering tasks have been performed independently in both domains. Traditionally, the transport network has been quite inflexible, and changes have often required a long time to occur. However, recent developments in the control plane allow flexibility in the transport network, making it possible to set up and tear down circuits on demand. In this light, multilayer traffic engineering has been proposed to jointly manage both IP and transport layers, with the aim of optimizing the use of resources. This paper aims to describe the rationale behind multilayer traffic engineering, demonstrate its feasibility and quantify its advantages in terms of cost effectiveness. Also, this work takes a look at the different choices in performing the multilayer operation, in terms of control plane implementation and equipment integration. Finally, the paper presents a report on multilayer traffic engineer experimentation which proves its feasibility and show a preliminary techno-economic case study of the multilayer operation.     

Dynamic link sleeping reconfigurations for green traffic engineering

The high volume of energy consumption has become a great concern to the Internet community because of high energy waste on redundant network devices. One promising scheme for energy savings is to reconfigure network elements to sleep mode when traffic demand is low. However, due to the nature of today's traditional IP routing protocols, network reconfiguration is generally deemed to be harmful because of routing table reconvergence. To make these sleeping network elements, such as links, robust to traffic disruption, we propose a novel online scheme called designate to sleep algorithm that aims to remove network links without causing traffic disruption during energy‐saving periods. Considering the nature of diurnal traffic, there could be traffic surge in the network because of reduced network capacity. We therefore propose a complementary scheme called dynamic wake‐up algorithm that intelligently wakes up minimum number of sleeping links needed to control such dynamicity. This is contrary to the normal paradigm of either reverting to full topology and sacrificing energy savings or employing on‐the‐fly link weight manipulation. Using the real topologies of GEANT and Abilene networks respectively, we show that the proposed schemes can save a substantial amount of energy without affecting network performance.     

面向卫星网络的流量工程路由算法

针对卫星网络链路长时延、拓扑时变等特征,将链路传输时延引入并基于MPLS网络中源-目的节点对已知这一先验知识,提出了一种面向卫星网络的MPLS流量工程路由算法。该算法基于卫星网络时变拓扑模型的卫星拓扑快照,定义链路初始权重为链路剩余带宽、传输时延的综合函数,在为当前节点对建路时考虑其余节点对将来建路的可能需求计算链路的关键度,在此基础上通过链路权重的动态调整及延期选用实现流量工程,从而优化卫星网络的链路利用。实验表明,此算法在请求拒绝数、吞吐量、平均跳数及平均时延等方面性能都有较理想的提升。     

Bandwidth borrowing‐based QoS approach for adaptive call admission control in multiclass traffic wireless cellular networks

This paper proposes a QoS approach for an adaptive call admission control (CAC) scheme for multiclass service wireless cellular networks. The QoS of the proposed CAC scheme is achieved through call bandwidth borrowing and call preemption techniques according to the priorities of the traffic classes, using complete sharing of the available bandwidth. The CAC scheme maintains QoS in each class to avoid performance deterioration through mechanisms for call bandwidth degradation, and call bandwidth upgrading based on min–max and max–min policies for fair resource deallocation and reallocation, respectively. The proposed adaptive CAC scheme utilizes a measurement‐based online monitoring approach of the system performance, and a prediction model to determine the amount of bandwidth to be borrowed from calls, or the amount of bandwidth to be returned to calls. The simulation‐based performance evaluation of the proposed adaptive CAC scheme shows the strength and effectiveness of our proposed scheme. Copyright © 2011 John Wiley & Sons, Ltd.     

Multidimensional PRMA with prioritized Bayesian broadcast-a MACstrategy for multiservice traffic over UMTS

Multidimensional packet reservation multiple access is proposed as a medium-access control (MAC) strategy for the uplink channel of the UTRA (UMTS terrestrial radio access) time-division/code-division multiple-access (TD/CDMA) mode to benefit from efficient statistical multiplexing on the large common pool of available resources (i.e., slots defined both in time and code domain). A prioritized Bayesian broadcast algorithm is derived to stabilize multidimensional packet reservation multiple access (MD PRMA) and to allow for access delay discrimination of four different access classes. Access delay spread can be selected, and trading voice-dropping ratio against data-access delay is possible. To control multiple-access interference, Bayesian broadcast can be combined with load-based access control. The performance of both frequency-division duplex (FDD) and time-division duplex (TDD) mode is evaluated, the latter particularly relevant for TD/CDMA. For mixed voice, Worldwide Web (WWW) browsing, and e-mail traffic, the UMTS WWW model is used, while the e-mail traffic model is derived here     

大规模高速网络流量工程研究

主要讨论互联网主干上的流量工程。由于现在路由协议使网络的低效率和新的应用的出现，迫切要求发展新的技术、引进流量工程的观点来处理这些问题。介绍了MPLS等的新的IP交换技术及其相关的路由算法；讨论了在IP主干上电话传输技术。     

埋入电容式多层印制板的研制

研究埋入电容多层板的制作工艺。通过试验验证电容容值与电容设计方法的关系,多层板生产流程中层压、热风整平工序对电容容值的影响;通过热冲击试验、老化试验等试验验证了埋入电容的容值在环境试验中的稳定性。通过一系列试验验证了埋入电容具有高温稳定性,可以在多层板内实现多个埋置电容层。可靠性试验证明埋置电容具有很好的稳定性和很高的可靠性。     

A cost effective approach for survivable multicast traffic grooming in bidirectional multiwavelength ring networks

In this paper, we address the problem of survivable multicast traffic grooming in WDM bidirectional ring networks. The rapid growth of multicast applications such as video conferencing, distance learning, and online auction, has initiated the need for cost-effective solutions to realize multicasting in WDM optical networks. Many of these applications, being time critical and delay sensitive, demand robust and fault-tolerant means of data communication. The end user traffic demands in metro environment are in fractional bandwidth as compared to the wavelength channel capacity. Providing survivability at connection level is resource intensive. Hence cost-effective solutions that require minimum resources for realizing survivable multicasting are in great demand. In order to realize multicast traffic grooming in bidirectional ring networks, we propose a node architecture based on Bidirectional Add Drop Multiplexers (BADM) to support bidirectional add/drop functionality along with traffic duplication at each node. We also propose two traffic grooming algorithms, namely Survivable Grooming with Maximum Overlap of Sessions (SGMOS) and Survivable Grooming with Rerouting of Sessions (SGRS). Extensive simulation studies reveal that the proposed algorithms consume minimum resources measured in terms of BADM grooming ports, backup cost, and wavelengths.     

Improved traffic sign recognition algorithm based on YOLOv4-tiny

This study offers an enhanced yolov4-tiny traffic sign identification method for easy deployment on mobile or embedded devices to address the difficulties of a high number of parameters, low recognition accuracy, and poor real-time performance of traffic sign recognition models in complex scenarios. The yolov4-tiny network serves as the model’s foundation. To begin, Octave Convolution is incorporated into the backbone network to eliminate low-frequency feature redundancy, lowering the number of parameters in the model and enhancing computational efficiency. Second, the convolutional block attention module is employed to improve the recognition accuracy of small and medium-sized targets by strengthening the weights of traffic sign regions and suppressing the weights of invalid features. Finally, in the feature fusion stage, the Feature Pyramid Networks structure is replaced with the Simplified Path Aggregation Network structure to improve the fusing of shallow feature information with deep semantic knowledge and lower the miss detection rate even more On the TT100K data set as well as on CCTSDB dataset, the experimental results suggest that our technique can achieve good recognition performance. With a 16MB model size, our solution improves the mean average precision by 3.5 percent and the Frame Per Second by 12.5 f/s when compared to the yolov4-tiny algorithm. Our method outperforms yolov4-tiny in terms of recognition accuracy and detection speed, and it can easily meet the real-time requirements for traffic sign recognition.     

光互联网中基于集成模型的流量工程研究

光互联网是一种简洁、高效、经济的网络体系结构,流量工程是其中的一个重要方面．文章在对IP层和光层流量工程进行分析的基础上指出了重叠模型流量工程的弊端,提出在光互联网中应采取集成模型的流量工程,并对其机制进行了研究,同时还对如何优化IP层和光层的流量工程代价分配进行了分析。