Connection management for multiwavelength optical networking

This paper describes the connection management research done by the Network Control and Management (NC&M) task force under the multiwavelength optical networking (MONET) program. MONET is sponsored by the Defense Advanced Research Project Agency (DARPA) the US Government Department of Defense, with participation from Bellcore, AT&T, Lucent Technologies, several government agencies, and regional Bell operating companies. MONET's vision is to develop a flexible reliable high-capacity high-performance cost-effective national optical network based on multiwavelength fiber optic technology. As an important component in realizing this vision, the MONET program includes the architecture and design of a prototype network control and management system for MONET's reconfigurable wavelength-division multiplexing (WDM) all-optical network. The primary objectives of the prototype research work are to develop the architecture and framework for managing national-scale transparent reconfigurable WDM optical networks and to demonstrate the feasibility of the NC&M prototype system in a field experiment network in Washington, DC. This prototype system allows the program participants to conduct experiments and gain experience in the management and operations of reconfigurable optical networks. This paper describes the connection management aspects of the prototype system, addressing issues such as the management architecture, information model, and provisioning algorithms of the prototype management system     

A next-generation optical regional access network

We describe an optical regional access network which combines electronic IP routing with intelligent networking functionality of the optical WDM layer. The optical WDM layer provides such networking functions as network logical topology reconfiguration, optical flow switching to offload traffic and bypass IP routers, wavelength routing of signals, protection switching and restoration in the optical domain, and flexible network service provisioning by reconfigurable wavelength connectivity. We discuss key enabling technologies for the WDM layer and describe their limitations. The symbiosis of electronic and optical WDM networking functions also allows support for heterogeneous format traffic and will enable efficient gigabit-per-second user access in next-generation Internet networks     

Distributed dynamic grooming routing and wavelength assignment in WDM optical mesh networks

The bandwidth of a wavelength channel in WDM optical networks is very high compared to the user’s requirements for various applications. Therefore, there is a scope for better utilization of channel bandwidth by traffic grooming, in which several user’s channels are multiplexed for transmission over a single channel. Several research works have been reported on traffic grooming routing and wavelength assignment (GRWA) for static and dynamic traffic pattern under centralized environment. Distributed dynamic grooming routing and wavelength assignment (DDGRWA) is a new and quite unexplored area in WDM optical mesh networks. This article introduces the concept of distributed traffic grooming in WDM mesh networks which also includes virtual topology construction, reconfiguration, routing and wavelength assignment in the distributed environment assuming incoming traffic to be dynamic in nature. We have also presented simulation results of our algorithm on dynamically generated traffic under various network topologies.     

Design and cost performance of the multistage WDM-PON accessnetworks

The advantages of employing passive optical architectures in the access network have been largely recognized. Particularly, recent developments in optical technologies have made the realization of wavelength division multiplexing passive optical networks (WDM PONs) feasible and cost-effective. These networks are more future-proof than conventional PONs, thanks to their intrinsic optical transparency and their extremely high transmission capacity. A very useful optical routing device, called waveguide grating router, is the basic building-block of new PON architectures capable of connecting a large number of users or to improve the use of the optical bandwidth. In this paper, we analyze the connectivity of WDM PONs composed of multiple stages of WGR devices. A design tool is also presented which is able to easily evaluate the connectivity functions of complex WDM PONs. The feasibility of these architectures is discussed by considering the costs and the technological limitations on the optical components     

WDM全光网网络管理系统的设计与实现

基于波长路的ＷＤＭ全光网是下一代高速宽带光纤网络的首选技术，如何对它进行有效而灵活的管理是目前研究的热点。ＳＨＡＯＮＥＴ是国内自主开发的第一个ＷＤＭ全光试验网，它具有自己网络管理系统，可以实现配置管理、性能管理和故障管理。本报导了ＳＨＡＯＮＥＴ网络的设计和它基于ＳＮＭＰ的实现。     

Performance analysis of multicast routing and wavelength assignment protocol with dynamic traffic grooming in WDM networks

The need for on‐demand provisioning of wavelength‐routed channels with service‐differentiated offerings within the transport layer has become more essential because of the recent emergence of high bit rate Internet protocol (IP) network applications. Diverse optical transport network architectures have been proposed to achieve the above requirements. This approach is determined by fundamental advances in wavelength division multiplexing (WDM) technologies. Because of the availability of ultra long‐reach transport and all‐optical switching, the deployment of all‐optical networks has been made possible. The concurrent transmission of multiple streams of data with the assistance of special properties of fiber optics is called WDM. The WDM network provides the capability of transferring huge amounts of data at high speeds by the users over large distances. There are several network applications that require the support of QoS multicast, such as multimedia conferencing systems, video‐on‐demand systems, real‐time control systems, etc. In a WDM network, the route decision and wavelength assignment of lightpath connections are based mainly on the routing and wavelength assignment (RWA). The multicast RWA's task is to maximize the number of multicast groups admitted or minimize the call‐blocking probability. The dynamic traffic‐grooming problem in wavelength‐routed networks is generally a two‐layered routing problem in which traffic connections are routed over lightpaths in the virtual topology layer and lightpaths are routed over physical links in the physical topology layer. In this paper, a multicast RWA protocol for capacity improvement in WDM networks is designed. In the wavelength assignment technique, paths from the source node to each of the destination nodes and the potential paths are divided into fragments by the junction nodes and these junction nodes have the wavelength conversion capability. By using the concept of fragmentation and grouping, the proposed scheme can be generally applied for the wavelength assignment of multicast in WDM networks. An optimized dynamic traffic grooming algorithm is also developed to address the traffic grooming problem in mesh networks in the multicast scenario for maximizing the resource utilization and minimizing the blocking probability. Copyright © 2011 John Wiley & Sons, Ltd.     

A scheduling application for WDM optical networks

Optical networking using WDM technology has matured considerably, and commercial WDM network equipment and WDM network control and management prototypes have appeared. To use such a network efficiently, a scheduling facility and its enabling mechanisms have to be provided. This scheduling facility should be integrated to interoperate with the rest of the network control and management software such as connection manager or signaling daemon. We present a scheduling application to address this need. The architecture for the application and its key components are presented. Agent-related enabling mechanisms are introduced to monitor the optical signal quality and collect performance measurements. A resource broker is used to manage the communication and interoperability between agents and the application. An event service is developed to decouple the communication between the agents and the scheduling application, and to enable the communication among the agents themselves. The scheduling application consists of the quality of signal information and threshold objects, current network usage, history data module, scheduling module, and access to a performance database. To provide traffic control and high network resource utilization, the application is equipped with wavelength scheduling algorithms. An experimental study for the basic scheduling algorithms has been conducted over the MONET DC network.     

On the future of wavelength routing networks

This article discusses the possible applications for optical networks based on wavelength division multiplexing and how they compete and complement current high-speed networks (SONET, ATM). We first outline the best-case scenario for this technology and describe the spectrum of proposed optical networks (WDM links, passive optical access networks, broadcast-and-select networks, and wavelength routing networks). Then we focus on wavelength routing networks and describe their advantages and disadvantages relative to other competing alternatives for very-high-speed networks. Finally, we analyze the different markets for such networks in the telco and data communications arena     

Virtual Source Based Multicast Routing in WDM Optical Networks

Wavelength-division multiplexed (WDM) networks using wavelength-routing are considered to be potential candidates for the next generation wide-area backbone networks. Multicasting is the ability to transmit information from a single source node to multiple destination nodes and is becoming an important requirement in high-speed networks. As WDM technology matures and multicast applications become increasingly popular, supporting multicast routing at the WDM layer becomes an important and yet a challenging topic. This paper concerns with the problem of optical multicast routing in WDM networks. A few nodes in the network may have wavelength conversion and/or splitting capabilities. In this paper, a new multicast tree construction algorithm is proposed. This algorithm is based on a concept called virtual source. A virtual source is a node having both the splitting and wavelength conversion capabilities. By exploiting the presence of virtual source nodes, the proposed algorithm achieves improved performance. To further improve the performance, the algorithm assigns priorities to nodes based on their capabilities. The effectiveness of the proposed algorithm is verified through extensive simulation experiments.     

Scalable WDM access network architecture based on photonic slotrouting

This paper introduces an approach to solving the fundamental scalability problem of all-optical packet switching wavelength-division multiplexing (WDM) access networks. Current optical networks cannot be scaled by simply adding nodes to existing systems due to the accumulation of insertion losses and/or the limited number of wavelengths. Scalability through bridging requires, on the other hand, the capability to switch packets among adjacent subnetworks on a wavelength basis. Such a solution is, however, not possible due to the unavailability of fast-switching wavelength sensitive devices. In this paper, we propose a scalable WDM access network architecture based on a recently proposed optical switching approach, termed photonic slot routing. According to this approach, entire slots, each carrying multiple packets (one on each wavelength) are “transparently” routed through the network as single units so that wavelength sensitive data flows can be handled using fast-switching wavelength nonsensitive devices based on proven technologies. The paper shows that the photonic slot routing technique can be successfully used to achieve statistical multiplexing of the optical bandwidth in the access network, thus providing a cost-effective solution to today's increasing bandwidth demand for data transmissions     

The arrayed-waveguide grating-based single-hop WDM network: an architecture for efficient multicasting

Research on multicasting in single-hop wavelength-division-multiplexing (WDM) networks has so far focused on networks based on the passive star coupler (PSC), a broadcast device. It has been shown that multicasting performance is improved by partitioning multicast transmissions into multiple multicast copies. However, the channel bottleneck of the PSC, which does not allow for spatial wavelength reuse, restricts the multicast performance. We investigate multicasting in a single-hop WDM network that is based on an arrayed-waveguide grating (AWG), a wavelength routing device that allows for spatial wavelength reuse. In our network, optical multicasting is enabled by wavelength-insensitive splitters that are attached to the AWG output ports. Multicasts are partitioned among the splitters and each multicast copy is routed to a different splitter by sending it on a different wavelength. We demonstrate that the spatial wavelength reuse in our network significantly improves the throughput-delay performance for multicast traffic. By means of analysis and simulations, we also demonstrate that, for a typical mix of unicast and multicast traffic, the throughput-delay performance is dramatically increased by transmitting multicast packets concurrently with control information in the reservation medium access control protocol of our AWG-based network.     

Architectures and technologies for high-speed optical data networks

Current optical networks are migrating to wavelength division multiplexing (WDM)-based fiber transport between traditional electronic multiplexers/demultiplexers, routers, and switches. Passive optical add-drop WDM networks have emerged but an optical data network that makes full use of the technologies of dynamic optical routing and switching exists only in experimental test-beds. This paper discusses architecture and technology issues for the design of high performance optical data networks with two classes of technologies, WDM and time division multiplexing (TDM). The WDM network architecture presented stresses WDM aware Internet protocol (IP), taking full advantage of optical reconfiguration, optical protection and restoration, traffic grooming to minimize electronics costs, and optical flow-switching for large transactions. Special attention is paid to the access network where innovative approaches to architecture may have a significant cost benefit. In the more distant future, ultrahigh-speed optical TDM networks, operating at single stream data rates of 100 Gb/s, may offer unique advantages over WDM networks. These advantages may include the ability to provide integrated services to high-end users, multiple quality-of-service (QoS) levels, and truly flexible bandwidth-on-demand. The paper gives an overview of an ultrahigh-speed TDM network architecture and describes recent key technology developments such as high-speed sources, switches, buffers, and rate converters     

Operation of WDM networks with different wavelength conversioncapabilities

We study the impact of wavelength conversion capability on wavelength routing WDM networks with fixed shortest-path routing. We propose a method for implementing wavelength routing in a WDM network with partial wavelength conversion capability. Simulation results show that such partial wavelength conversion networks provide a performance in between that of wavelength continuous networks and those with full conversion capability. In addition, it can be seen that only limited wavelength conversion capability is enough to provide a performance close to that of a network with full conversion. Analytical and simulation bounding results for the full and no conversion cases have also been provided     

Dynamic Routing and Wavelength Assignment Using Cost Based Heuristics in WDM Optical Networks

Dynamic routing and wavelength assignment problem in optical networks is a two-step problem that is influenced by the choice of a successful optimal path selection and wavelength assignment. Proper selection techniques reduce the number of wavelengths required in the network and thereby improves traffic grooming. Heuristic algorithms and integer linear programming models help in selection of route and wavelength separately. Hence, the computation time is large which makes the system slow. A cost function is computed which uses independent parameters in the network for the selection of route and wavelength for a call. The heuristic reduces computation time by combining the search of route and wavelength to be assigned. In addition, the network performance is analyzed with and without alternate routing along with proposed heuristics. The selection of proper route and wavelength finding technique is very essential since it improves the grooming factor of the network thereby allowing more traffic support by the network. Our objective is to investigate and propose a cost based heuristics for dynamic traffic routing and wavelength Assignment in WDM optical networks. For this we plan to develop cost functions and heuristics to compute the route and wavelength assignment strategy. Here, our objective is to reduce the computation time for selection of route and wavelength assignment strategy by weighted cost function. The function has to include network parameters for its processing. Our work provides an overview about DRWA by applying cost based heuristics in WDM networks. This paper explains the proposed cost function and its applications in line with selection of independent parameters. The details of other functions like cost function formulation, hop-based route assignment, available wavelength based route assignment, mathematical analysis of proposed cost function are also explained. Results and discussions based on the findings are presented.

     

AWG-based metro WDM networking

A plethora of metropolitan area wavelength-division multiplexing networks have been proposed and examined in recent years with the aim to alleviate the bandwidth bottleneck between increasingly higher-speed local/access networks and high-speed backbone networks. Many of the considered metropolitan area networks use the arrayed waveguide grating as an optical building block. As we review in this article, in ring, interconnected ring, and meshed metro WDM networks, the AWG is typically used to realize wavelength multiplexers, demultiplexers, or optical add-drop multiplexers without capitalizing on spatial wavelength reuse. By using the AWG as a wavelength router, highly efficient star metro WDM networks can be realized due to extensive spatial wavelength reuse. We give an overview of star metro WDM networks that are able to meet modular upgradability, transparency, flexibility, efficiency, reliability, and protection requirements of future metro networks. AWG-based star networks also enable an evolution path of ring networks toward highly efficient and fault-tolerant hybrid star-ring metro network solutions.     

The NGI ONRAMP test bed: reconfigurable WDM technology for nextgeneration regional access networks

Next generation internet optical network for regional access using multi-wavelength protocols (NGI ONRAMP) is a pre-competitive consortium sponsored by DARPA. Its mission is to develop architectures, protocols, and algorithms for wavelength division multiplexing (WDM)-based regional access networks that will effectively support the NGI. A reconfigurable WDM test bed is being built to demonstrate some of the key thrusts of the consortium, including dynamic service provisioning and optical flow switching, service protection in the optical domain, medium access control protocols, and network control and management geared for the efficient transport of Internet traffic over WDM networks. The ONRAMP test bed will consist of a feeder network connecting via access nodes to distribution networks on which the end users reside. ONRAMP network reconfiguration is enabled by access nodes that contain both optical and electronic switching components, allowing data traffic to be routed all-optically through the network or to be switched and aggregated by electronic Internet protocol (IP) routers. This paper describes the goals and basic architecture of the ONRAMP test bed, as well as the design, construction, and characterization of the network access nodes. To illustrate test bed operation, we demonstrate optical flow switching over the test bed that achieves Gb/s throughput of TCP data between end user workstations     

Adaptive alternate routing in WDM networks and its performance tradeoffs in the presence of wavelength converters

Routing in wavelength-routed all-optical WDM networks has received much attention in the past decade, for which fixed and dynamic routing methods have been proposed. Taking into account the observation that wavelength-routed all-optical WDM networks are similar to circuit-switched voice networks, except with regard to wavelength conversion, we propose an adaptive alternate routing (AAR) scheme for wavelength-routed all-optical WDM networks. A major benefit of AAR is that it can operate and adapt without requiring an exchange of network status, i.e., it is an information-less adaptive routing scheme. The scope of this work is to understand this scheme in its own right since no other dynamic routing schemes are known to have the information-less property. In this paper, we conduct a systematic study of AAR with regard to factors such as the number of converters, load conditions, traffic patterns, network topologies, and the number of alternate paths considered. We observe that the routing scheme with multiple alternate routes provides more gain at a lower load instead of requiring any nodes to be equipped with wavelength converters. On the other hand, the availability of wavelength converters at some nodes, along with adaptive routing, is beneficial at a moderate to high load without requiring all nodes to be equipped with wavelength converters. We also observed that a small number of alternate routes considered in a network without wavelength converters gives a much better performance than a network with full wavelength converters and fewer alternate routes. Throughout this study, we observed that the proposed adaptive alternate routing scheme adapts well to the network traffic condition.     

The scalable lightwave network

In principle, an optical network employing wavelength routing, wavelength reuse, and multihop packet switching is modularly scalable to very large configurations in both the hardware and software sense. As such, it is a viable architecture for a new ATM-based telecommunications infrastructure The network architecture considered for a new, scalable, broadband telecommunications infrastructure is based on (1) the use of wavelength division multiplexing (WDM) and wavelength routing; (2) the translation of signals from one wavelength to another at the access stations; and (3) the use of multihop ATM packet switching. These principles permit networks to be built whose size is essentially unlimited     

Approaches to optical Internet packet switching

Wavelength-division multiplexing is currently being deployed in telecommunications networks in order to satisfy the increased demand for capacity brought about by the explosion in Internet use. The most widely accepted network evolution prediction is via an extension of these initial predominantly point-to-point deployments, with limited system functionalities, into highly interconnected networks supporting circuit-switched paths. While current applications of WDM focus on relatively static usage of individual wavelength channels, optical switching technologies enable fast dynamic allocation of WDM channels. The challenge involves combining the advantages of these relatively coarse-grained WDM techniques with emerging optical switching capabilities to yield a high-throughput optical platform directly underpinning next-generation networks. One alternative longer-term strategy for network evolution employs optical packet switching, providing greater flexibility, functionality, and granularity. This article reviews progress on the definition of optical packet switching and routing networks capable of providing end-to-end optical paths and/or connectionless transport. To date the approaches proposed predominantly use fixed-duration optical packets with lower-bit-rate headers to facilitate processing at the network-node interfaces. Thus, the major advances toward the goal of developing an extensive optical packet-switched layer employing fixed-length packets are summarized, but initial concepts on the support of variable-length IP-like optical packets are also introduced. Particular strategies implementing the crucial optical buffering function at the switching nodes are described, motivated by the network functionalities required within the optical packet layer     

An architecture for IP over WDM using time-division switching

This paper proposes an architecture for routing Internet protocol (IP) packets directly on optical networks. The use of label switching is assumed in the IP routers, while a new routing architecture is introduced to transport IP packets across an optical backbone network. The architecture is based on a two-tier multiplexing approach with wavelength division multiplexing (WDM) addressing the number of regional exchanges and time-division switching communicating among the hubs. Such an architecture not only has the advantages of simple network management and high efficiency with low latency; it also is scalable by addition of regional exchanges, hubs, and fibers