损伤感知的光网络连接指配的关键问题研究

在透明网络中,光信号由于受到物理损伤的影响而质量降低,这使得损伤感知的连接指配日益成为人们研究的热点.文章从架构、损伤模型和损伤感知的路由波长分配(IRWA)算法3方面研究了损伤感知的光网络连接指配的     

Lightpath routing for intelligent optical networks

An overview of current issues and challenges in lightpath routing for optical networks is given. An architecture is presented in which optical switches are deployed, usually in the core, to interconnect IP routers at the edges. Lightpath routing within this architecture follows the framework of generalized multiprotocol label switching. Our discussion pays particular attention to the aspects of optical routing that differ from routing in irrational IP networks. Such aspects include physical layer constraints, wavelength continuity, the decoupling of the control network topology from the data network topology, explicit routing with wavelength assignment, and diversity routing for fast protection. We also present an algorithmic framework for lightpath computation, highlighting the issue of wavelength continuity and the differences between lightpath computation and traditional IP route computation     

Applying PTF/VTF routing policies in multilayer IP/MPLS-based ASON/GMPLS multi-domain networks

The IP/MPLS-based ASON/GMPLS hybrid network architecture enables the interaction between the IP layer and the optical dense wavelength division multiplexing (DWDM) layer. This architecture makes it possible to transfer huge amounts of traffic data on DWDM networks, while supporting Internet Protocol (IP)-based service applications. Additionally, this architecture provides a unified routing scenario, which allows the dynamic routing in both the IP layer and/or optical layer. Cross- layer routing has been addressed in single domain networks scenarios, where the routing policies Physical Topology First (PTF) and Virtual Topology First (VTP) have been proposed and applied. However, applying cross-layer routing using both routing topology policies PTF and VTF has not been investigated in a multi-domain networks scenario yet. In this study, we address this issue and propose a routing scheme to establish traffic connections in the optical WDM layer and the IP layer, which makes the applicability of PTF and VTF in multilayer multi-domain network feasible.     

Benefits of the use of impairment constraint routing in optical networks

In transparent optical networks, the optical signal accumulates the effects of all physical impairments present along the path it traverses. The conventional selection of signal paths based on e.g. shortest path routing without considering the signal quality and its association with the physical impairments does not always provide the optimum solution in terms of network performance such as blocking and resource utilization. This paper proposes an impairment constraint based routing algorithm to achieve an optimal combination of physical and networking performance taking into account all physical linear impairments including noise, chromatic and polarization mode dispersion, crosstalk and filter concatenation effects in an integrated approach. The performance of a typical metropolitan area network is examined and the improvement achieved when using the proposed approach compared to the conventional shortest path routing is demonstrated.     

多粒度全光网中的多层联合路由

多粒度交换技术利用波带级路由以及光纤级路由,可有效降低光交叉连接器的复杂度.但多粒度交换增加了光网络的逻辑层次结构,使得网络中的路由与资源分配问题更为复杂,因此,在多粒度全光网中实现多层联合路由是提高网络性能的关键.本文对多粒度交叉连接结构进行了分析,并对多粒度全光网中的多层联合路由问题进行了研究.     

波长路由网络选路时的光信号质量限制研究

光网络中,路由与波长分配(RWA)算法是最优化网络性能的核心问题之一,传统的RWA算法都假设光网络的物理层状态是理想的,即不存在光信号传输损伤的问题.通过对这个缺陷的分析,将光信号的传输损伤问题充分考虑到路由与波长分配算法中,从算法的角度来实现对光信号的传输保护,这样做不仅能有效防止业务的物理损伤阻塞,还能极大地提高光网络的性能.     

A dynamic impairment-aware networking solution for transparent mesh optical networks - [Topics in optical communications]

Core networks of the future will have a translucent and eventually transparent optical structure. Ultra-high-speed end-to-end connectivity with high quality of service and high reliability will be realized through the exploitation of optimized protocols and lightpath routing algorithms. These algorithms will complement a flexible control and management plane integrated in the proposed solution. Physical layer impairments and optical performance are monitored and incorporated in impairment-aware lightpath routing algorithms. These algorithms will be integrated into a novel dynamic network planning tool that will consider dynamic traffic characteristics, a reconfigurable optical layer, and varying physical impairment and component characteristics. The network planning tool along with extended control planes will make it possible to realize the vision of optical transparency. This article presents a novel framework that addresses dynamic cross-layer network planning and optimization while considering the development of a future transport network infrastructure.     

Integrated IP/WDM routing in GMPLS-based optical networks

Future transport networks will have to cope with the continuous growth of IP traffic. Furthermore, transport networks need to evolve so as to drastically reduce both deployment costs and operating expenses. A reasonable strategy to achieve this goal consists of simplifying the network architecture by reducing the number of layers. Assuming a peer model IP over optical network, we propose an integrated routing strategy that takes into account constraints and dynamic occupancy of both the IP and optical layers. The collaboration of both layers in the routing process leads to optimization of network performance. The main emphasis is on the implementation requirements of this grooming functionality using GMPLS-TE mechanisms. Simulation results show the benefits obtained by applying this strategy.     

Network architecture for optical path transport networks

This paper proposes a new layered transport network architecture on which the WDM optical path network can be effectively created. The optical path network will play a key role in the development of the transport network that will realize the bandwidth-abundant B-ISDN. This paper extends the layered transport network architecture described in ITU-T Recommendation G.803 which is applied in existing SDH networks. First, we elucidate an application example of WDM optical path networks. Next, we propose a new layered architecture for WDM-based transport networks that retains maximum commonality with the layered architectures developed for existing B-ISDN networks. The proposed architecture is composed of circuit layer networks, electrical path layer networks, optical layer networks, and physical media (fiber) networks. The optical layer is divided into an optical path layer and an optical section layer. The optical path layer accommodates electrical paths. Optical section layer networks are divided into optical multiplex section (OMS) layer networks and optical repeater section (ORS) layer networks. The OMS layer network is concerned with the end-to-end transfer of information between locations transferring or terminating optical paths, whereas the ORS layer is concerned with the transfer of information between individual optical repeaters. Finally, a detailed functional block model of WDM optical path networks, the function allocation of each layer, and an optical transport module (OTM) are developed     

Evaluation of optical core networks based on the CANON architecture

Clustering of nodes in optical networks has been proven to be an efficient way to serve end-to-end connectivity. However, clustering requires specific topological characteristics, or alternatively the introduction of significant alterations of an existing topology to achieve the expected performance improvements. The comparison of future dynamic optical networking technologies should therefore include in the set of initial assumptions, apart from the statistical properties of the traffic load, the network topology to draw conclusions regarding the efficiency as well as feasibility and scalability of the proposed solutions. In this article, we show how node clustering under the CANON architecture can be applied in real-life core networks and provide superior performance compared to conventional burst switching techniques in terms of blocking, resource utilization and power consumption.     

Distributed optical control plane for dynamic lightpath establishment in translucent optical networks based on reachability graph

In transparent optical networks, physical layer impairments (PLIs) incurred by non-ideal optical transmission media accumulate along an optical path, and the overall effect determines the optical feasibility of the lightpaths. In addition, transparent optical networks suffer from inefficient wavelength utilization, as a connection request may be rejected because of non-availability of a common wavelength on all the links along the chosen route. To increase optical reach, resource utilization, and average call acceptance ratio (and hence revenues), network operators are resort to translucent optical networks. In these networks a limited number of regenerators are placed at a selected set of nodes. In this scenario development of an optical control plane which is aware of PLIs, location and number of regenerators, is of paramount importance for on-demand lightpath provisioning. In this paper, we propose a novel approach of constructing a reachability graph of the physical network considering PLIs and regenerators. If there is no transparent path in the physical network, we route the connections with multiple transparent segments on the reachability graph. We propose efficient mechanisms and corresponding GMPLS protocol extensions for impairment and regenerator aware routing and wavelength assignment (IRA-RWA) in translucent optical networks. The simulation results suggest that our proposed approach together with LSP stitching signaling mechanism is feasible to implement and close to deployment.     

Architectures and performance of optical packet switching nodes for IP networks

As new bandwidth-hungry Internet protocol (IP) services are demanding more and more capacity, transport networks are evolving to provide a reconfigurable optical layer in order to allow fast dynamic allocation of wavelength-division-multiplexing (WDM) channels. To achieve this goal, optical packet-switched systems seem to be strong candidates as they allow a high degree of statistical resource sharing, which leads to an efficient bandwidth utilization. In this paper, we propose an architecture for optical packet-switched transport networks, together with an innovative switching node structure based on the concept of per-packet wavelength routing. The traffic performance of such node when loaded by a typical IP traffic is evaluated through computer simulation; packet loss probability and average delay performance are shown for various load conditions.     

On Multicast Routing for Wavelength-Routed WDM Networks with Dynamic Membership

Future broadband networks must support integrated services and offer flexible bandwidth usage. In our previous work in [1], we explored the optical link control (OLC) layer on the top of optical layer that enables the possibility of bandwidth on-demand (BoD) service directly over wavelength division multiplexed (WDM) networks. Today, more and more applications and services such as video-conferencing software and Virtual LAN service require multicast support over the underlying networks. Currently, it is difficult to provide wavelength multicast over optical switches without optical/electronic conversions although the conversion takes extra cost. In this paper, based on the proposed wavelength router architecture (equipped with ATM switches to offer O/E and E/O conversions when necessary), a dynamic multicast routing algorithm is proposed to furnish multicast services over WDM networks. The goal is to join a new group member into the multicast tree so that the cost, including the link cost and the optical/electronic conversion cost, is kept as low as possible. The same algorithm can be applied to other wavelength routing architectures with redefinition of electronic copy cost. The effectiveness of the proposed wavelength router architecture as well as the dynamic multicast algorithm is evaluated by simulation.     

A joint scheduling,power control,and routing algorithm for ad hoc wireless networks

In wireless networks there is strong coupling among the traditional layers of the architecture, and these interactions cannot be ignored. One example is the interaction between routing in the network layer and access control in the MAC layer. Another one is the coupling between power control in the physical layer and scheduling in the MAC layer. In this paper, we assume a TDMA-based wireless ad hoc network and provide a centralized algorithm of joint power control, scheduling, and routing. Simulation results show the improvement of the network performance, in terms of throughput, delay, and power consumption, through use of the joint algorithm. Energy efficiency is another important aspect of ad hoc networking, and is considered in our algorithm. Our simulation also shows the trade-off between energy consumption and network throughput or delay performance.     

A hierarchical scheme on achieving all-IP communication between WSN and IPv6 networks

The paper proposes a hierarchical scheme on implementing all-IP communication between wireless sensor networks and IPv6 networks. The paper proposes the cluster-tree architecture for all-IP wireless sensor networks which is consistent with the IPv6 Internet architecture. Based on the cluster-tree architecture, the paper proposes the hierarchical IPv6 address configuration algorithm where the IPv6 configuration for cluster members in different clusters can be performed simultaneously, so the IPv6 configuration delay is shortened. Based on the proposed cluster-tree architecture and the IPv6 address configuration algorithm, the paper proposes the hierarchical routing scheme in the link layer where the intermediate nodes only need to deal with the frame header in the link layer without processing the headers in the above layers, so the routing delay is shortened and the power consumption is reduced. From both theoretical perspective and simulative perspectives, the paper analyze the performance parameters of the proposed scheme. And the data results show that the performance of the proposed scheme is better.     

Design and analysis of a dynamically reconfigurablethree-dimensional FPGA

This paper presents the design and analysis of a dynamically reconfigurable field programmable gate array (FPGA) that consists of three physical layers: routing and logic block layer, routing layer, and memory layer. The architecture was developed using a methodology that examines different architectural parameters and how they affect different performance criteria such as speed, area, and reconfiguration time. The resulting architecture has high performance while the requirement of balancing the areas of its constituent layers is satisfied     

A 1+1 protection architecture for optical burst switched networks

High-capacity optical backbone networks protect their premium customers' information flows by routing two copies of the customer's data over disjoint paths. This scheme, known as 1+1 protection, provides extremely rapid recovery from network failures. We propose an architecture by which 1+1 protection can be extended to optical burst switched (OBS) networks. This architecture is designed by modifying the diversity routing architecture that was originally proposed for nonoptical packet networks and recently applied to networks employing the generalized multiprotocol label switched (GMPLS) architecture. We extend the architecture developed for just-in-time OBS signaling to support 1+1 protection. We also examine design issues that are raised by a difference in the propagation delays of the two disjoint paths across the OBS network. We show that a sufficiently large difference in the propagation delays can cause performance degradations that may result in an unsatisfactory quality-of-service on the protected connection. We examine the impact of this delay mismatch on restoration performance, probability of burst loss, and jitter. Through analysis and simulations, it is discussed how these negative effects can be eliminated.     

Toward alternative high-speed network concepts: the SWIFTarchitecture

An approach to communication architectures for high-speed networks which provides efficient, adaptive communication for any traffic distribution is presented. It is based on a concept of dynamic sharing of communication resources which is obtained from the following three-tier SWIFT architecture. At the physical layer the high-speed communication system is based on the use of several lower speed channels or frequencies. At the data link layer, driven by hardware simplicity considerations, the SWIFT architecture uses a fixed time-slotted allocation of subchannels, in which each node is required to transmit or receive over only a single, predetermined, subchannel at a time. To provide adaptive channel access control, while preserving the data link hardware simplicity, a network layer is added. This layer introduces multihop adaptive channel (frequency) routing on the inherently broadcast communication medium. The routing concept provides dynamic sharing of communication channels and buffers, leading to a fully distributed adaptive bandwidth control. An analytic model for analyzing the performance of the multilayered architecture is developed. It shows that for homogeneous or heterogeneous traffic requirements the approach provides throughput/delay performance superior to that found in existing communication systems     

Impairment-aware ordered scheduling in dual-header optical burst switched networks

Optical burst switching (OBS) is a promising technology for bridging the gap between optical wavelength switching and optical packet switching. Optical signal transmission quality is subject to various types of physical impairment introduced by optical fibers, switching elements, or other network components. The signal degradation due to physical impairment may be significant enough such that the bit-error rate of received signals is unacceptably high at the destination, rendering the signal to not usable. In this article, based on earlier study, we study the burst-scheduling problem in OBS networks using two control packets for each data burst, taking into account physical impairment effects. We propose a burst-scheduling algorithm that accommodates incoming bursts by primary path routing, deflection routing, and burst scheduling. We design an admission control mechanism to use network resources efficiently. At an OBS node, the proposed algorithm schedules bursts for transmission by searching for available resources as well as verifying signal quality. Our simulation results demonstrate that the proposed algorithm is effective in terms of reducing the burst-blocking probability.