Performance analysis for the dynamic virtual path bandwidth control method in ATM networks

Broadband ISDN (integrated services digital network) should provide various kinds of communication services for multimedia traffic, including voice, computer data, still picture and motion video, and an ATM (asynchronous transfer mode) technology is expected to satisfy those demands. In ATM networks, a VP (virtual path) concept is introduced for simplifying the network resource management. However, if the bandwidth of each VP is fixed, it cannot absorb traffic load fluctuation. In this case, it is likely to happen that one VP has no remaining bandwidth while other VPs on the same physical link have free capacities. Another extremity is that a VP is not introduced, and that all VCs along the same physical link share the whole bandwidth of the link. This can achieve an efficient use of the link, but it apparently requires complicated call set-up procedures. In this paper, we propose a new dynamic VP bandwidth control method, in which the bandwidth allocated to each VP is dynamically changed according to traffic fluctuation. More specifically, in the case that multiple VPs are multiplexed on the same link between two nodes, when the utilization of some VP is increased, that VP requests an additional bandwidth. When the traffic load becomes low and the utilization of a VP is decreased, a part of the assigned bandwidth is released. We consider two methods for this purpose; one is the basic method in which the bandwidth increase request is issued after the VP bandwidth is exhausted. The other is the look-ahead method where the bandwidth increase is requested in advance before the bandwidth starvation. An approximate analysis for the above methods is provided, and the validation of its accuracy is assessed by comparing with simulation results. Through numerical examples, we show that our methods can provide performance improvement in terms of call loss probabilities of each VP.     

Network planning based on virtual path bandwidth management

Periodical performance evaluation and adaptive resource assignment, already proposed as performance-oriented management, seems to be the most suitable strategy for network planning under demand uncertainty. In this paper, we exploit the inherent capability of ATM networks to rearrange dynamically the already installed resources, and propose performance-oriented management combined with virtual path bandwidth (VPB) control for the planning of the extensions of bandwidth capacities of virtual paths (VPs) and transmission links of the network. We define a large network optimization problem and solve it by a rigorous, analytical procedure. The optimization model comprises specific requirements of the network-planning problem and a bandwidth distribution scheme ensuring network reliability. We reveal the efficiency of the proposed scheme by applying it on a model network, considering two realistic case-studies of network-traffic evolution. We show that in the presence of VPB control: (a) the initial distribution of the total bandwidth to VPs is of no importance, since it can be adaptively rearranged according to the offered traffic, (b) the network is well used and bandwidth investment could be saved, and (c) whenever additional bandwidth must be installed in VPs which have an unanticipated bad grade-of-service, time savings result. We present the network performance in detail, in figures, and compare this with the performance of the network in the absence of VPB control.     

Comparison of virtual path bandwidth assignment and routing methods

The virtual path (VP) can simplifyAtm network management by minimizing connection routing and admission costs, and by facilitating the layered control of resources. However, fully exploiting these advantages may lead to a large number of relatively low capacity virtual paths travelling on each physical link. If each VP is treated as a separate unit, as is commonly assumed, low path capacities will lead to low network utilisation. This paper carefully examines the trade-off between simplification through traffic separation and improved efficiency due to traffic consolidation. We review existing vp bandwidth assignment and control techniques, and propose a new vp tagging control method. A comparison shows that by permitting resource sharing between paths it is possible to influence significantly the trade-off between simplified network management and multiplexing gain from traffic consolidation.     

Building networks for the wide and local areas using asynchronoustransfer mode switches and synchronous optical network technology

Sandia National Laboratories is using a set of evolving technologies to develop a standards-based approach to wide- and local-area networking, which offers the potential of gigabit speeds. In particular, asynchronous transfer mode (ATM) switches and synchronous optical network (SONET) technologies were used to build a supercomputing network between its California and New Mexico sites and now is being deployed in the local-area environment. The progress of these endeavors and the lessons learned are discussed     

Priority shaping of traffic streams sharing a policed virtual path in an ATM network

Traffic streams with differing service requirements, sharing a single contract for use of a policed virtual path in an ATM network, may be jointly shaped to make the best use of bandwidth available in the path. The shaper may use the information about the network policer to perform self-policing with a form of priority service to ensure satisfactory levels of cell loss and delay for both real-time and non-real-time traffic. Two such shapers are considered assuming a mean bit-rate contract with the network in which a leaky-bucket mechanism performs the policing function. The performance of the shapers is analysed using Markov-modulated models of bursty traffic sources and stochastic fluid methods, and the analytical results are corroborated by simulations. The choice of the shaper type and optimization of the shaper design parameters are discussed using correlated and non-correlated source models.     

Dynamic allocation of resources to virtual path agents

One of the major problems faced in operating large networks is the enormous amount of processing and communications overhead required for setting up and tearing down the large number of connections maintained by the network. ATM and MPLS aim at solving these problems via the Virtual Path (VP) mechanism which is used to group together the connections. When a need for setting up a connection rises, the request and its resource allocation are processed by the VP agent and not by the network, thus reducing the processing cost significantly. An important question in the design of these networks is the amount of network resources to be dynamically allocated to and held by the VP agents; too high allocation will result with bandwidth resource waste, while too low allocation will result with heavy connection set-up and tear-down processing load. In this paper we deal with this problem, and at deriving simple operational rules to determine the amount of bandwidth resources to be held by the various VP agents, while balancing between bandwidth waste and connection processing overhead. We formulate the resource allocation problem by accounting both for bandwidth utilization and for connection processing constraints. Recognizing the complexity of the problem, we use a decomposition approach in which we first analyze the single link problem and then propose to use this solution as a building block in constructing algorithms for the whole network. For the single link problem we realize that the pure problem is too complex and thus formulate an approximate model and derive the optimal allocation for it. The optimal rule is expressed as a closed-form square-root allocation. Extensive numerical examination shows that the rule proposed yields very efficient allocations. For the full network problem, we propose to capitalize on the closed form structure of the single link problem solution and use it in devising algorithms for the whole network.     

Hardware implementation of fair queuing algorithms for asynchronoustransfer mode networks

Providing quality-of-service guarantees in both cell- and packet-based networks requires the use of a scheduling algorithm in the switches and network interfaces. These algorithms need to be implemented in hardware in a high-speed switch. The authors present a number of approaches to implement scheduling algorithms in hardware. They begin by presenting a general methodology for the design of timestamp-based fair queuing algorithms that provide the same bounds on end-to-end delay and fairness as those of weighted fair queuing, yet have efficient hardware implementations. Based on this general methodology, the authors describe two specific algorithms, frame-based fair queuing and starting potential-based fair queuing, and discuss illustrative implementations in hardware. These algorithms may be used in both cell switches and packet switches with variable-size packets. A methodology for combining a traffic shaper with this class of fair queuing schedulers is also presented for use in network interface devices, such as an ATM segmentation and reassembly device     

A simple bandwidth management strategy based on measurements ofinstantaneous virtual path utilization in ATM networks

A new connection admission control method based on actual virtual path traffic measurements is proposed to achieve high bandwidth efficiency for various types of traffic. The proposed method is based on the measurement of instantaneous virtual path utilization, which is defined as the total cell rate of the active virtual channels normalized by the virtual path capacity. A low-pass filter is used to determine the instantaneous virtual path utilization from crude measurements. A smoothing coefficient formula is derived as a function of the peak rate of the virtual channel. The residual bandwidth is derived from the maximum instantaneous utilization observed during a monitoring period. Simulation shows that the proposed method achieves statistical multiplexing gains of up to 80% of the limit possible with optimum control for similar traffic sources. It can be implemented with very simple hardware. The admission decision is simple: the requested bandwidth is compared with the residual bandwidth. This method is therefore well suited for practical asynchronous transfer mode switching systems     

Power-aware virtual optical network provisioning in flexible bandwidth optical networks [Invited]

Considering the virtual network infrastructure as a service, optical network virtualization can facilitate the physical infrastructure sharing among different clients and applications that require optical network resources. Obviously, mapping multiple virtual network infrastructures onto the same physical network infrastructure is one of the greatest challenges related to optical network virtualization in flexible bandwidth optical networks. In order to efficiently address the virtual optical network (VON) provisioning problem, we can first obtain the virtual links’ order and the virtual nodes’ order based on their characteristics, such as the bandwidth requirement on virtual links and computing resources on virtual nodes. We then preconfigure the primary and backup paths for all node-pairs in the physical optical network, and the auxiliary graph is constructed by preconfiguring primary and backup paths. Two VON mapping approaches that include the power-aware virtual-links mapping (PVLM) approach and the power-aware virtual-nodes mapping (PVNM) approach are developed to reduce power consumption for a given set of VONs in flexible bandwidth optical networks with the distributed data centers. Simulation results show that our proposed PVLM approach can greatly reduce power consumption and save spectrum resources compared to the PVNM approach for the single-line rate and the mixed-line rate in flexible bandwidth optical networks with the distributed data centers.     

SDN环境下的虚拟网络动态切换技术

SDN的出现开展了计算机虚拟网络模式新的转变,实现了将控制层面与数据转发分离的功能。利用OpenFlow协议对控制器与交换机进行交流。针对网络传输的能耗问题,提出虚拟网络动态切换技术,在该系统中虚拟机之间通信有两条路径可供选择,即光交换机和电交换机。通过对交换机的切换,实现虚拟网络流量的整合,减少物理网络资源的冗余浪费,从而达到优化数据网络能耗的目的。通过Ping与Netperf这两个测试工具测出丢包率、延迟及流量值,这些数值的变化证明了所提系统可正常运行。     

Dynamic recovery for survivable virtual network embedding

Network virtualization is a promising way to overcome the current ossification of the Intemet. It is essential challenge to find effective, efficient and robust embedding algorithms for recovering virtual network. The virtual network mapping algorithm based on integer programming which was proposed months ago. But it did consider the faults of physical network resources, which is so called survivable virtual network embedding （VNE） problem. Previous strategies for enabling survivability in network virtualization focused on providing protection for the physical network or enhancing the virtual networks by providing backup physical resources in advance, and treated all the physical failures as link failures. In the article, a dynamic recovery method is proposed to solve the survivable virtual network embedding problem based on the integer programming VNE algorithm. The dynamic recovery method doesn＇t need to backup physical resources and it makes more substrate resources which can be used in the embedding. The dynamic recovery process will be activated only when physical failures occur. Different algorithms are used to recovery node and link failures. Simulations show that the method helps to recover almost all of physical failures by finding the substitute nodes and paths, and its performance is very close to that of pure VNE method without considering physical failures.     

一种均衡物理资源和网络带宽的虚拟机部署方法研究

随着互联网的发展,云计算的发展越来越快,云资源管理平台也受到了越来越多的关注。云计算资源管理系统是云计算体系的大脑,具有重要的研究价值。针对目前虚拟机部署未能均衡考虑能耗与网络流量的问题,文章设计了一种结合能耗和网络均衡优化的虚拟机部署算法。该算法采用K-均值聚类,利用改进的皮尔逊相关系数进行相似度计算,最终为虚拟机在所有的候选宿主机中选择合适的宿主机。     

基于KVM的虚拟化网络模式实现的技术分析

云计算堪称近年来计算机网络领域的一次变革,其核心虚拟化技术得到了广泛的重视。KVM是其中一种高效的虚拟化技术,结合QEMU,KVM对虚拟机提供了丰富的网络支持。本文对QEMU-KVM主流的虚拟化网络模式的实现进行技术分析,该分析对教学实践活动和企业实践应用具有一定借鉴意义。     

Virtual path bandwidth allocation in multiuser networks

We consider a multiuser network that is shared by noncooperative users. Each user sets up virtual paths that optimize its own selfish performance measure. This measure accounts for the guaranteed call level quality of service, as well as for the cost incurred for reserving the resource. The interaction among the user strategies is formalized as a noncooperative game. We show that the game has a unique Nash equilibrium and that it possesses a certain fairness property. We investigate the dynamics of this game and prove convergence to the Nash equilibrium of both a Gauss-Seidel scheme and a Jacobi scheme. We extend our study to various general network topologies. Finally, the formal results and some extensions thereof are tested by emulating the schemes on an experimental network     

Adaptive filtering with bandwidth constraints in the feedback path

This paper introduces a new, adaptive-filter-based controller that shows advantageous properties from the viewpoint of its communication requirement. The algorithm is called signed-error filtered-x LMS (SE-FxLMS). Its novelty is characterized by the fact that it makes possible data compression in the feedback path of adaptive-filter-based control loops in a very simple way. This feature is especially useful in such closed-loop systems where the feedback signals are transmitted over a low-bandwidth communication channel. This is a typical case in so-called networked control systems (NCS), where the communication is carried out over a shared communication channel, e.g., using a wireless sensor network. The paper introduces an analysis of the algorithm as well.     

网络化虚拟测控系统的设计

为满足计算机专业教学和测控仪器开发的需要,设计了基于网络、虚拟仪器和SOPC技术的网络化虚拟测控系统。该系统由PCI接口卡、基于NiosII软核的SOPC数据采集系统组成,使用Labview技术构建了C/S模式的远程数据采集和管理体系结构,并基于Windows DDK与VC++语言开发了PCI接口驱动程序。实际应用表明,该系统具有开放性、灵活性以及易用性等优点,达到了预期目的。     

Priority-based minimum interference path multicast: routing algorithm in optical virtual private network

While the “Virtual Private Network (VPN) over Internet” is cost-effective and flexible, it suffers from the difficulty of providing adequate transmission capacity for high bandwidth services. Hence a Dense Wavelength Division Multiplexing (DWDM) based “Optical VPN (OVPN)” technology has been regarded as a good alternative for realizing the future VPN services. To improve the transparency and data rate of OVPN, it is critical to consider the problem of Routing and Wavelength Assignment (RWA) for transmission capacity utilization. This paper proposes a Priority-based Minimum Interference Path Multicast Routing (PMIPMR) algorithm, a new routing algorithm which finds alternative routes based on node priorities and Virtual Source (VS) nodes that has both splitting and wavelength conversion, and then chooses a path that does not interfere with potential future multicast session requests when congestions occur in the network. The PMIPMR algorithm reduces blocking rate significantly and increases the wavelength utilization by avoiding congestion in future multicast session requests. We measured the performance of the proposed algorithm in terms of blocking rate and the resource utilization. The simulation results demonstrate that the PMIPMR algorithm is superior to the previous multicast routing algorithms using the Capability-based-Connection algorithm based on Capability-based-Priority and Spawn-from-VS methods.     

Neural network based-time optimal sliding mode control for an autonomous underwater robot

This paper presents a robot control system using sliding mode control (SMC) as a core controller. The SMC switches according to the Pontryagin’s time optimal control principle, in which the solution is obtained by using neural network approach. The control system is implemented on Chalawan, a six-degree-of-freedom autonomous underwater robot developed at Mechatronics Laboratory, AIT. The control system can be applied to underwater robots, which have similar kind of architecture. Performance of the proposed controller is compared with various classical SMCs and conventional linear control system. The comparison detail results such as controller performance and error phase portrait are presented and analyzed. Such comparisons ensure the implementation success and prove it as a real time-optimal controller. The results also show the controller’s effective capabilities in plant nonlinearity and parameters uncertainties.     

GPON中的动态带宽分配

首先介绍了吉比特无源光网络(GPON)的复用结构和所承载的业务,随后就GPON的关键技术之一——动态带宽分配作了详细论述,分别从带宽分配的功能、对象和过程这几个方面作了介绍,最后比较了GPON和宽带无源光网络(BPON)在动态带宽分配方面的不同。     

Optimization strategy of virtual machine online migration with awareness of application characteristics and network bandwidth migration

Firstly the experiments to verify the relationship between the number of dirty memory pages and application characteristics which exist in virtual machine migration was conducted.Then,different virtual machine application characteristics were perceived,with which the number of dirty memory pages produced during the migrations was predicted by the use of GM(1,N) grey prediction model.At the same time,using residual correction to adjust error makes results more reliable.According to the prediction of memory dirty pages,network bandwidth was adjusted and reserved.Compared with the traditional pre-copy strategy,the given experiments show that the optimized strategy proposed can improve the performance of network and reduce migratory cost for the memory-intensive and network-intensive applications.