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.     

Resource management with virtual paths in ATM networks

A virtual path connection (VPC) is a labelled path which can be used to transport a bundle of virtual channel connections (VCCs) and to manage the resources used by these connections. The virtual network is organized as a collection of VPCs which form a VPC, or logical, overlay network. If the VPCs are permanent or semi-permanent and have reserved capacity, establishing new VCCs requires simple connection admission decisions at the VPC terminators of existing VPCs. This would enable faster connection establishment since transit nodes are not involved in the connection setup. The virtual path concept also allows the possibility of segregating traffic types according to quality of service requirements. However, the extent to which VPC provisioning is able to improve network efficiency is dependent on the resource management decisions that determine the VPC topology and capacity allocations. The article surveys resource management using virtual paths in an ATM network. Of interest are techniques which modify the VPC topology and capacity assignments in order to adapt to changing traffic conditions and possible network failures. The resource management activities employed to facilitate such adaptation can be categorized by the timescale on which they operate. On the shortest timescale are strategies for dynamically making minor changes to the VPC topology or capacity assignments. On a somewhat longer timescale are strategies for making more widespread modifications to the VPC overlay network. This would be appropriate for traffic changes based on time of day and for recovering from network failures. Finally, on an even longer timescale, strategies may be employed to design a general VPC overlay network, to be used at startup or after major network upgrades. Solutions to VPC resource management for each of these timescales are discussed     

An Elastic Sub-carrier and Power Allocation Algorithm Enabling Wireless Network Virtualization

Wireless mobile network virtualization enables physical mobile network operators (PMNO) to partition their network resources into smaller slices and assign each slice to an individual virtual mobile network operator and then manages these virtual networks in a more dynamic and cost-effective fashion. How a PMNO allocates resources to individual slices while ensuring resource elasticity is a key issue. This paper presents a resource allocation algorithm in such a network virtualization scenario where resource considered here includes both sub-carriers and transmission power. The overall algorithm involves the following two major processes: firstly to virtualize a physical wireless network into multiple slices each representing a virtual network, where resources are allocated elastically based on traffic loads and channel state information during virtualization; secondly, to carry out physical resource allocation within each virtual network (or slice). In particular the paper adopts orthogonal frequency division multiplexing as its physical layer to achieve more efficient resource utilization. A multi-step dynamic optimization approach is proposed to achieve sub-carrier allocation using binary integer programming and power allocation using nonlinear programming. The aim is to achieve the following design goals: virtual network isolation, and resource efficiency. The simulation results show that the above goals have been achieved.     

Design Philosophy and Hardware Implementation for Digital Subscriber Loops

This paper presents various requirements and configurations in the information network system (INS) NTT's version of the integrated services digital network (ISDN)- such as field trials, and technologies and equipment design of the digital subscriber loop using balanced wire pairs. The main aspects characterizing digital subscriber loops, are a customer access structure, a digital transmission system on existing subscriber loops, and customer interface. A configuration of two-wire digital subscriber loops with two customer access channels, which is adopted in the field trials, will be described. The time-shared two-wire digital transmission and power feeding methods on subscriber loops are discussed. The common mode rejection ratio (CMRR) is discussed in detail, since CMRR is one of the main factors which affects the transmission ability of balanced wire pairs. A proposed self-clocked four-wire customer interface utilizes time division multiplexing technique. The digital subscriber loop operates on a call-by-call basis for link establishment to avoid excessive power dissipations as well as to avoid impairments caused by crosstalk from other lines within a cable. Its design objectives and implementation are also discussed.     

轻量级容器化技术驱动的虚拟网络部署研究

近年来,由于5G、物联网等技术的快速发展,网络规模越来越庞大,对于网络应用的要求随之提高,网络应用的各项性能则需要在较为复杂的网络中进行测试,将现实生活中结构复杂的网络用于应用性能测试的可行性不高。因此,对于SDN(Software-Defined Networking,SDN)网络开发而言,迫切的需要能够进行测试的仿真平台。市面上常见的网络测试工具尽管可以实现网络仿真,但存在保真度低、可视化支持差等问题。在本设计中,采用轻量级虚拟化技术,搭建虚拟化的网络模拟仿真平台——网络魔镜。将真实网络协议“照进”虚拟环境,摆脱现有模拟网络仿真工具的局限性,对基于Docker容器搭建起来的轻量级的虚拟网络,可以方便地对其进行计算机网络的相关研究。     

Covering all the bases: network interconnectivity and its legal implications

We live in a world connected by many different networks. Network components can be physical, virtual, or a combination of both. Some network industries rely on physical infrastructures, such as electrical power and telephony networks, while others are mainly organized around virtual network standards, such as the Internet and the software industry. The control and use of network infrastructures and standards in network industries not only reflects technological developments and business decisions, but also entails legal constraints. This article will discuss the concept of network effects, the relevance of network infrastructures and standards, and some legal frameworks regarding the control and use of network infrastructures and standards.     

Power‐efficient routing for SDN with discrete link rates and size‐limited flow tables: A tree‐based particle swarm optimization approach

Software‐defined networking is a promising networking paradigm for achieving programmability and centralized control in communication networks. These features simplify network management and enable innovation in network applications and services such as routing, virtual machine migration, load balancing, security, access control, and traffic engineering. The routing application can be optimized for power efficiency by routing flows and coalescing them such that the least number of links is activated with the lowest link rates. However, in practice, flow coalescing can generally overflow the flow tables, which are implemented in a size‐limited and power‐hungry ternary content addressable memory (TCAM). In this paper, a set of practical constraints is imposed to the software‐defined networking routing problem, namely, size‐limited flow table and discrete link rate constraints, to ensure applicability in real networks. Because the problem is NP‐hard and difficult to approximate, a low‐complexity particle swarm optimization–based and power‐efficient routing (PSOPR) heuristic is proposed. Performance evaluation results revealed that PSOPR achieves more than 90% of the optimal network power consumption while requiring only 0.0045% to 0.9% of the optimal computation time in real‐network topologies. In addition, PSOPR generates shorter routes than the optimal routes generated by CPLEX.     

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     

On topology improvement of a packet radio network by power control

The packet radio network (PRN) is an attractive architecture for wireless data communication. The code assignment problem in PRN is a classical problem that has been extensively studied. However, we observe that the power control issue has been ignored by most works but may have significant impact on the PRN's performance. Given a set of PRN stations, the network topology can be changed by adjusting each station's transmission power. All existing works, nevertheless, assume that the network topology is given before solving the code assignment problem. We regard code assignment as an independent problem and show how to improve the network topology by power adjustment without violating the original code assignment. The improvement in topology (such as more links in the network) may result in improvement in network throughput. Through simulations, we demonstrate that, although the code assignment problem is NP-complete, our power adjustment schemes can easily improve the network performance by about 10% with polynomial costs.     

On the Maximum Protection Problem in IP-over-WDM Networks Using IP LSP Protection

In dynamic IP-over-WDM networks efficient fault-management techniques become more difficult since as demands change with time the optimal logical topology varies as well. Changes in the virtual topology should be done with care because working IP LSPs routed on top of a virtual topology should not be interrupted. Reconfiguration of the virtual topology may also affect precomputed backup IP LSPs to be activated in case of failure meaning that backup IP LSPs would need to be recomputed after any change in the virtual topology. A good sense solution can be the dimensioning of the virtual topology for a worst case traffic scenario, having as goal the minimization of the network cost, for example, and then route dynamic IP LSPs on this virtual topology. The virtual topology would remain unchanged as long as possible, that is, until changes in the virtual topology are considered to bring considerable benefits. Since data services over IP are essentially of a best-effort nature, protection could be provided, using IP LSP protection, only when bandwidth is available in the virtual topology. The computation of backup IP LSPs does not interfere with working IP LSPs meaning that no service interruption will exist. Such a strategy, considered in this paper, allows resources to be used efficiently, since free bandwidth is used for backup purposes, while the normal delivery of traffic is guaranteed in peak traffic situations although having no protection guarantees. Our main objective is to quantify the spare capacity, which can be used for restoration (backup) purposes, over a virtual topology designed and optimized to carry a traffic scenario with no survivability and QoS requirements. We analyse the maximum protection (MP) problem in such IP-over-WDM network environment. Protection is provided to IP LSP requests whenever possible through bandwidth reservation in a backup IP LSP on the virtual topology. Besides the mathematical formalization of the MP problem, an upper bound and heuristic algorithms are proposed and evaluated. The traffic considered includes IP LSPs of different granularities and is the worst case traffic scenario for which the network should be dimensioned.     

The Tempest: a framework for safe, resource assured, programmablenetworks

Most research in network programmability has stressed the flexibility engendered by increasing the ability of users to configure network elements for their own purposes, without addressing the larger issues of how such advanced control systems can coexist both with each other and with more conventional ones. The Tempest framework presented here extends beyond the provision of simple network programmability to address these larger issues. In particular, we show how network programmability can be achieved without jeopardizing the integrity of the network as a whole, how network programmability fits in with existing networks, and how programmability can be offered at different levels of granularity. Our approach is based on the Tempest's ability to dynamically create virtual private networks over a switched transport architecture (e.g., an ATM network). Each VPN is assigned a set of network resources which can be controlled using either a well-known control system or a control system tailored to the specific needs of a distributed application. The first level of programmability in the Tempest is fairly coarse-grained: an entire virtual network can be programmed by a third party. At a finer level of granularity the Tempest allows user supplied code to be injected into parts of an operational virtual network, thus allowing application specific customization of network control. The article shows how the Tempest framework allows these new approaches to coexist with more conventional solutions     

Optical signal processing for lightwave communications networks

A number of optical signal processing functions that might be potentially important for future lightwave communication networks are described. An optical network with a distribution capacity of 100 HDTV channels is considered along with how such a network can be implemented using the following functional subsystems: frequency converters; transmitter banks; modified (wavelength division multiplexing) WDM demultiplexers; and tunable optical receivers. Discussed are the key network-level issues: the power budget, the channel separation, and the overall rationale for selection of multiplexing techniques. A hardware implementation of the functional subsystems using three basic building blocks-tunable amplifiers/filters, phase locked loops, and comb generators-is discussed     

Adaptive link layer strategies for energy efficient wireless networking

Low power consumption is a key design metric for portable wireless network devices where battery energy is a limited resource. The resultant energy efficient design problem can be addressed at various levels of system design, and indeed much research has been done for hardware power optimization and power management within a wireless device. However, with the increasing trend towards thin client type wireless devices that rely more and more on network based services, a high fraction of power consumption is being accounted for by the transport of packet data over wireless links [28]. This offers an opportunity to optimize for low power in higher layer network protocols responsible for data communication among multiple wireless devices. Consider the data link protocols that transport bits across the wireless link. While traditionally designed around the conventional metrics of throughput and latency, a proper design offers many opportunities for optimizing the metric most relevant to battery operated devices: the amount of battery energy consumed per useful user level bit transmitted across the wireless link. This includes energy spent in the physical radio transmission process, as well as in computation such as signal processing and error coding. This paper describes how energy efficiency in the wireless data link can be enhanced via adaptive frame length control in concert with adaptive error control based on hybrid FEC (forward error correction) and ARQ (automatic repeat request). Key to this approach is a high degree of adaptivity. The length and error coding of the atomic data unit (frame) going over the air, and the retransmission protocol are (a) selected for each application stream (ATM virtual circuit or IP/RSVP flow) based on quality of service (QoS) requirements, and (b) continually adapted as a function of varying radio channel conditions due to fading and other impairments. We present analysis and simulation results on the battery energy efficiency achieved for user traffic of different QoS requirements, and describe hardware and software implementations.     

Multi-hour, multi-traffic class network design for virtualpath-based dynamically reconfigurable wide-area ATM networks

The virtual path (VP) concept has been gaining attention in terms of effective deployment of asynchronous transfer mode (ATM) networks in recent years. In a recent paper, we outlined a framework and models for network design and management of dynamically reconfigurable ATM networks based on the virtual path concept from a network planning and management perspective. Our approach has been based on statistical multiplexing of traffic within a traffic class by using a virtual path for the class and deterministic multiplexing of different virtual paths, and on providing dynamic bandwidth and reconfigurability through virtual path concept depending on traffic load during the course of the day. In this paper, we discuss in detail, a multi-hour, multi-traffic class network (capacity) design model for providing specified quality-of-service in such dynamically reconfigurable networks. This is done based on the observation that statistical multiplexing of virtual circuits for a traffic class in a virtual path, and the deterministic multiplexing of different virtual paths leads to decoupling of the network dimensioning problem into the bandwidth estimation problem and the combined virtual path routing and capacity design problem. We discuss how bandwidth estimation can be done, then how the design problem can be solved by a decomposition algorithm by looking at the dual problem and using subgradient optimization. We provide computational results for realistic network traffic data to show the effectiveness of our approach. We show for the test problems considered, our approach does between 6% to 20% better than a local shortest-path heuristic. We also show that considering network dynamism through variation of traffic during the course of a day by doing dynamic bandwidth and virtual path reconfiguration can save between 10% and 14% in network design costs compared to a static network based on maximum busy hour traffic     

Internetworking based on cell switch router-architecture andprotocol overview

This paper describes an internetworking architecture and related protocol overview based on routers that have asynchronous transfer mode (ATM) cell switching capability in addition to conventional Internet protocol (IP) packet forwarding. The proposed architecture can provide high-throughput and low-latency switched paths for individual application flows or a group of application flows while retaining current router-based internetworking architecture. The proposed router is able to establish the switched path based on the characteristics of flows, e.g., arrival of a data packet with specific upper layer protocols or arrival of more than a certain amount of data packets in a predetermined period, as well as by the reception of an IP-layer resource reservation request, such as resource reservation protocol (RSVP). One important feature that is provided by the proposed router is interoperability with the emerging ATM network platform specified by the ATM Forum and the telecommunications sector of the International Telecommunications Union (ITU-T). The proposed routers can be interconnected with each other over the point-to-point synchronous optical network link as well as over the ATM network platform, which provides permanent virtual channel, virtual path, or switched virtual channel (SVC) services. That enables network carriers to provide Internet/intranet services as well as others, such as telephony, ATM/time division multiplexing leased line, or native ATM SVC services     

An Energy and Performance Exploration of Network-on-Chip Architectures

In this paper, we explore the designs of a circuit-switched router, a wormhole router, a quality-of-service (QoS) supporting virtual channel router and a speculative virtual channel router and accurately evaluate the energy-performance tradeoffs they offer. Power results from the designs placed and routed in a 90-nm CMOS process show that all the architectures dissipate significant idle state power. The additional energy required to route a packet through the router is then shown to be dominated by the data path. This leads to the key result that, if this trend continues, the use of more elaborate control can be justified and will not be immediately limited by the energy budget. A performance analysis also shows that dynamic resource allocation leads to the lowest network latencies, while static allocation may be used to meet QoS goals. Combining the power and performance figures then allows an energy-latency product to be calculated to judge the efficiency of each of the networks. The speculative virtual channel router was shown to have a very similar efficiency to the wormhole router, while providing a better performance, supporting its use for general purpose designs. Finally, area metrics are also presented to allow a comparison of implementation costs.      

Control of distributed generation

Summary  Distributed generation (DG), whose installed capacity is increasing rapidly, can be defined as low rating generation that is neither planned nor dispatched centrally and is usually connected to the distribution network. Appropriate control of DG can improve the performance of DG units without violating network constraints, and facilitate the effective participation of DG in power system and market operation. Two control levels, DG unit control and network control, are summarized. DG unit control is introduced based on three technologies: induction generators, synchronous generators and power electric converters. Effective network control can be built based upon active management concept. Finally, three DG control paradigms, MicroGrid, cell and virtual power plant, are discussed.      

Joint Algorithm of Channel Allocation and Power Control in Multi-channel Wireless Sensor Network

In the wireless sensor network, the interference incurred by another transmitter’s transmission may disturb other receivers’ correct receptions of packets, thus, the add of a new transmission must consider its effect on other transmissions. Additionally, in order to reduce the interference and increase QoS, multi-channel technology is introduced into wireless communication, but the energy cost by the channel switch increases with the interval of channels increasing. Based on the above analysis, we consider an energy efficient joint algorithm of channel allocation and power control (JCAPC) for wireless sensor network. In JCAPC, each link firstly establishes its available channel set on which the transmitter of the link can guarantee its transmission successfully and don’t disturb other receivers’ transmissions, and then each link chooses a channel from the available channel set according to the energy cost on anti-interference and channel switch. After that, we formulate power control on each channel as a non-cooperative game with utility function including Signal-to-Interference-and-Noise Ratio (SINR) price. In order to reduce the energy cost of the information exchange during the traditional game, we introduce the thought of game virtual playing, in which each link can decide its own transmission power by imitating the game among links with its once collected information. Consequently, JCAPC can not only increase the transmission efficiency but also reduce the nodes’ energy waste. Moreover, the existence of Nash Equilibrium (NE) is proven based on super-modular game theory, and it’s able to obtain the unique NE by relating this algorithm to myopic best response updates. The introduction of game virtual playing saves the energy cost of network further more by reducing the number of information exchange. Simulation results show that our algorithm can select a channel with good QoS using less energy consumption and provide adequate SINR with less transmit power, which achieves the goal of efficiently reducing energy waste.     

On capacity of cognitive radio networks with average interference power constraints

Cognitive radio (CR) has been considered as a promising technology to improve the spectrum utilization. In this paper we analyze the capacity of a CR network with average received interference power constraints. Under the assumptions of uniform node placements and a simple power control scheme, the maximum transmit power of a target CR transmitter is characterized by its cumulative distribution function (CDF). We study two CR scenarios for future applications. The first scenario is called the CR based central access network, which aims at providing broadband access to CR devices. In the second scenario, the so-called CR assisted virtual multiple-input multiple-output (MIMO) network, CR is used to improve the access capability of a cellular system. The uplink ergodic channel capacities of both scenarios are derived and analyzed with an emphasis on understanding the impact of numbers of primary users and CR users on the capacity. Numerical and simulation results suggest that the CR based central access network is more suitable for less-populated rural areas where a relatively low density of primary receivers is expected; while the CR assisted virtual MIMO network performs better in urban environments with a dense population of mobile CR users.     

Construction and maintenance of virtual backbone in wireless networks

In ad hoc wireless networks, there is no predefined infrastructure and nodes communicate with each other via peer communications. In order to make routing efficient in such networks the connected dominating set (CDS) can act as virtual backbone for the network. A smaller virtual backbone suffers less from the interference problem and incurs less maintenance overhead. Computing minimum CDS backbone is proven to be NP-Hard, it is therefore desirable to use efficient heuristic algorithms to find a virtual backbone of small size. Diameter and average backbone path length (ABPL) are other major criteria for evaluation of the backbone produced by an algorithm. In this paper, after giving a brief survey of classical CDS algorithms, two new centralized algorithms are described for the construction of the virtual backbone and their performance has been compared with five recent algorithms (two centralized and three distributed) along the parameters: size, diameter, and ABPL. The new algorithms perform better on most of the criteria. The re-construction of entire CDS upon movement or failure of a few nodes is very costly in terms of processing power, battery utilization, bandwidth utilization etc., as compared to maintaining the CDS for the affected nodes, since the re-construction of the CDS is to be performed for the whole network while maintenance involves the affected nodes and their neighbours only. A new distributed algorithm is described that maintains the virtual backbone on movement or failure of a single node. The overhead of CDS maintenance with this algorithm compares very favourably against that of re-construction.