Proceedings Volume 4585

Optical Networking

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Proceedings Volume 4585

Optical Networking

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Volume Details

Date Published: 17 October 2001
Contents: 8 Sessions, 40 Papers, 0 Presentations
Conference: Asia-Pacific Optical and Wireless Communications Conference and Exhibit 2001
Volume Number: 4585

Table of Contents

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Table of Contents

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  • Optical Packet Switching I
  • Routing and Wavelength Assignment
  • Implementation Issues I
  • Protection and Restoration
  • Optical Flow and Label Switching
  • Implementation Issues II
  • Poster Session
  • Section
Optical Packet Switching I
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Optical-label switching, MPLS, MPLambdaS, and GMPLS
This paper discusses the new architecture and protocol of Optical-Label switching in light of its interworking with MPLS and MPLambdaS networks. The dynamic and agile characteristics of Optical-Label switching indicate its support of diverse QoS, CoS and ToS services while interoperating packet and circuit switching. Optical-Label switching routers employ time, space and wavelength domain switching for contention resolution, and the interface with MPLS, MPLambdaS, or any client networks with proper signaling such as extension of GMPLS.
Buffering optical IP packets
Soon Hwa Chin, Ian Wright, Ivan Andonovic, et al.
A novel buffering mechanism for IP packets over WDM links is proposed by exploiting the packet nature. ACK packets which do not carry any payload can be singled out to be processed and stored purely in the electronic control plane without getting through the optical path which consists of the switching matrix and optical delay line buffers. An optical path is then reserved at the output for these ACK packets by extending the optical delay lines to be integral of ACK packets. Simulation results have shown an improvement both in the packet loss probability and the mean delay for using this scheme.
Hybrid contention-resolution scheme for an optical packet-switched network with self-similar IP traffic
We propose a novel optical-electrical hybrid contention-resolution scheme for optical packet-switched networks. This scheme exploits both electrical buffering at the ingress nodes and optical contention resolutions at the core nodes. It significantly improves the network's performance with a simple node architecture. By employing self-similar packet traffic with typical IP packet-size distribution, we demonstrate a packet-loss rate of less than 0.01 with average offered transmitter load up to 0.6 for a representative telecom network. Our results also show that the use of electrical buffering at the edge does not introduce any significant latency.
IP over fiber technologies: ATM/POS/SDL
Depeng Jin, Lieguang Zeng
The explosive growth of Internet traffic has created the need to transport IP over high-speed links such as fiber. Three main IP over fiber technologies have been developed: ATM, POS and SDL. As ATM has been widely researched and developed, this paper mainly discusses the POS and SDL. POS is a traditional mapping method of packets, and this paper presents the realization state machine of POS and analyzes the Probability of Packet Loss. SDL is a new framing protocol for variable/fixed length of packet, which extends the HEC-liking framing mechanism used in ATM. This paper analyzes this new protocol and gives the performance results such as MTTF and PFP. Finally, the comparison of POS and SDL is provided.
Routing and Wavelength Assignment
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Soft optics in intelligent optical networks
Chikong Shue, Yang Cao
In addition to the recent advances in Hard-optics that pushes the optical transmission speed, distance, wave density and optical switching capacity, Soft-optics provides the necessary intelligence and control software that reduces operational costs, increase efficiency, and enhances revenue generating services by automating optimal optical circuit placement and restoration, and enabling value-added new services like Optical VPN. This paper describes the advances in 1) Overall Hard-optics and Soft-optics 2) Layered hierarchy of Soft-optics 3) Component of Soft-optics, including hard-optics drivers, Management Soft-optics, Routing Soft-optics and System Soft-optics 4) Key component of Routing and System Soft-optics, namely optical routing and signaling (including UNI/NNI and GMPLS signaling). In summary, the soft-optics on a new generation of OXC's enables Intelligent Optical Networks to provide just-in-time service delivery and fast restoration, and real-time capacity management that eliminates stranded bandwidth. It reduces operational costs and provides new revenue opportunities.
Unified approach for wavelength switch routing connection management
Jesse Zhang
This paper discussed some requirements and issues for connection management in an optical wavelength routing switch in the context of a dynamically configurable wavelength management network environment. The wavelength connection management in the optical routing switch provides and manages the data path in the switch core for the configured end-to-end light path. Through a unique approach in design of the switching fabrics control and management, it is believed that a more scalable, flexible, and manageable optical wavelength routing switch architecture can be achieved. For editing purpose it is focused more on O-E-O model throughout this paper, although the contents would serve the same purpose to all optical model.
Path-protection routing and wavelength assignment in WDM mesh networks under shared-risk-group constraints
This study investigates the problem of fault management in a wavelength-division multiplexing (WDM)-based optical mesh network in which failures occur due to fiber cuts. In reality, bundles of fibers often get cut at the same time due to construction or destructive natural events, such as earthquakes. Fibers laid down in the same duct have a significant probability to fail at the same time. If two fibers reside in the same cable (bundle of fibers) or the same duct, we say that these two fibers are in the same Shared Risk Group (SRG). When path protection is employed, we require the primary path and the backup path to be SRG-disjoint, so that the network is survivable under single-SRG failures. Moreover, if two primary paths go through any common SRG, their backup paths cannot share wavelengths on common links. This study addresses the routing and wavelength-assignment problem in a network with path protection under SRG constraints. Off-line algorithms for static traffic is developed to combat single-SRG failures. The objective is to minimize total number of wavelengths used on all the links in the network. Both Integer Linear Programs (ILPs) and heuristic algorithms are presented and their performances are compared through numerical examples.
Sparse regeneration in a translucent WDM optical network
Xi Yang, Byrav Ramamurthy
Recent research implies that transparent optical WDM networks have difficulty in overcoming transmission impairments introduced by long-haul fibers and cascading optical components while opaque networks are not cost-efficient because a large number of wavelengths need optical-electronic and electronic-optical conversions at every intermediate node. This paper proposes an alternate approach to fully transparent and fully opaque optical networks for operating a wavelength routed optical network. In this paper, the architecture of regeneration node that performs sparse regeneration (or translucency) is modeled. Both static and dynamic regeneration schemes are discussed. The regeneration demands generated from call blocking and signal quality requirements are addressed. Two implementation strategies for incorporating sparse regeneration are introduced and algorithms are proposed for the regenerator placement, and their relative merits are studied.
Dynamic traffic grooming in optical WDM mesh networks with distributed control
Keyao Zhu, Biswanath Mukherjee
Wavelength-division multiplexing (WDM) is the promising technology to meet the rapid growth of Internet traffic. The next-generation optical WDM networks will have the capability of real-time provisioning of network capacity, providing interoperability between different optical and electronic networks, etc. An unified control plane that incorporates these desirable features is being designed and developed. Traffic grooming is a very important problem whose solution will enable us to fully develop such a control plane for next-generation optical networks. In this work, we study the network architectures for grooming-capable WDM networks and propose a routing algorithm that enables a WDM network to support dynamic grooming of traffic streams of different capacity granularities. Network performance, based on various node architectures, is investigated via simulations.
Priority-based wavelength assignment algorithm in WDM networks
Rongxi He, Zhizhong Zhang, Lemin Li, et al.
In this paper, a priority-based wavelength assignment algorithm, Dynamic Threshold Method (DTM), is proposed. A set of wavelengths, Preferred Wavelength Set (PWS), is pre-allocated for each priority request. Based on the usage of wavelength in the PWS of a priority request, a threshold is dynamically calculated to decide whether the wavelengths for the higher priority request can be allocated to the lower. By using DTM, the blocking probability of the high priority request is guaranteed to be a lower degree, and at the same time performance of the low priority request is improved. So the network's average blocking probability is minimized. Simulation results of the network performance show that the proposed algorithm performs well in different dynamic traffic load situation.
Implementation Issues I
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Adaptation technology between IP layer and optical layer in optical Internet
Wavelength division multiplexing (WDM) optical network provides a platform with high bandwidth capacity and is supposed to be the backbone infrastructure supporting the next-generation high-speed multi-service networks (ATM, IP, etc.). In the foreseeable future, IP will be the predominant data traffic, to make fully use of the bandwidth of the WDM optical network, many attentions have been focused on IP over WDM, which has been proposed as the most promising technology for new kind of network, so-called Optical Internet. According to OSI model, IP is in the 3rd layer (network layer) and optical network is in the 1st layer (physical layer), so the key issue is what adaptation technology should be used in the 2nd layer (data link layer). In this paper, firstly, we analyze and compare the current adaptation technologies used in backbone network nowadays. Secondly, aiming at the drawbacks of above technologies, we present a novel adaptation protocol (DONA) between IP layer and optical layer in Optical Internet and describe it in details. Thirdly, the gigabit transmission adapter (GTA) we accomplished based on the novel protocol is described. Finally, we set up an experiment platform to apply and verify the DONA and GTA, the results and conclusions of the experiment are given.
Signaling for fast restoration in heterogeneous optical mesh networks
Bala Rajagopalan, Debanjan Saha, Greg Bernstein, et al.
With the advent of optical mesh networks, certain new protection schemes have been defined. This encompasses both local span and end-to-end path protection. But the implementations of these protection schemes have so far been based on proprietary mechanisms developed by each vendor. This has made it virtually impractical to construct a heterogeneous network with interoperable mesh protection schemes. Also, while the notion of a standard IP-centric control plane for optical networks based on Generalized Multi-Protocol Label Switching (GMPLS) has gained wide acceptance, the work in this area has so far focused exclusively on connection provisioning rather than restoration. This paper defines standard, IP-based signaling protocols for restoration in optical mesh networks. These protocols focus on a new local span protection mode and end-to-end shared protection. The main requirements on these protocols are simplicity and speed. The signaling mechanisms described in this paper are complimentary to the GMPLS provisioning mechanisms.
Reliable optical network design
Guangzhi Li, Jennifer Yates, Dongmei Wang, et al.
Emerging optical networks will provide very high bandwidth connections to users. However, improving provisioning times and restoration capabilities after a network failure are important issues in evolving the optical networks. critical problems faced by optical network providers. The application of IP-based protocols to the optical network control plane has opened up new opportunities and challenges for network designers. Although much work has been done on standardization of the relevant protocols, the reliability of optical networks and their control plane needs further investigation. Based on our experience prototyping an IP based control plane, this paper discusses some general requirements and proposed solutions for reliable optical network design from a service and operational perspective. Our experiments suggest that a reliable IP based control plane for fast provisioning and restoration in optical network is feasible with careful design.
Optical SNR of OXC chains
Tao Qin, Hanyi Zhang, Xiaoping Zheng, et al.
We introduce a general model for the calculation of the optical signal-to-noise ratio (SNR) of the optical cross-connection (OXC) in optical networks in this paper. The impact of two power equalization schemes on the optical SNR is presented. We also point out the EDFA design principle for optimizing noise character of OXC chains.
Protection and Restoration
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Quality-of-service-based protection in MPLS control WDM mesh networks
Intelligent methods for automatic protection and restoration are critical in optical transport mesh networks. This paper discusses the problem of quality of service (QoS)-based protection in term of the protection-switching time and availability for end-to-end lightpaths in a WDM mesh network. We analyze the backup lightpath-sharing problem in such networks and study the correlation of the working lightpaths and its impact to the sharing of their backup lightpaths. We present a multi-protocol-label-switching (MPLS) control-based fully distributed algorithm to solve the protection problem. The proposed algorithm includes intelligent and fully automatic procedures to set up, take down, activate, restore, and manage backup lightpaths. It greatly reduces the required resources for protection by allowing the sharing of network resources by multiple backup lightpaths. At the same time, it guarantees, if possible, to satisfy the availability requirement even with resource sharing by taking the correlation of working lightpaths into consideration when deciding backup lightpaths. A simple analysis of the proposed algorithm in terms of computation, time, and message complexity indicates that the implementation of the algorithm is practical. The illustrative studies that compare the performance of 1:1, unlimited sharing, and QoS-based sharing backup algorithms indicates that QoS-based sharing achieves comparable performance as unlimited sharing, which is much better than the 1:1 backup scheme in terms of connection blocking probability, average number of connections in the network for a given offered load, and network-resource utilization.
Joint lightpath routing approach in survivable optical networks
Chunsheng Xin, Yinghua Ye, Sudhir Dixit, et al.
In optical networks, each single lightpath can offer huge bandwidth to carry the client traffic. In many cases, the clients require the optical network to provide the survivability of the carried traffic. Hence how to route the working and protection paths to better utilize the wavelength resource is an important challenge for service providers. In this paper, we propose a joint lightpath routing approach to select the working and protection paths for the dynamic traffic. The proposed routing approach attempts to perform individual optimization on the path selection for each call request. The performance of the joint lightpath routing approach has been examined against the traditional lightpath routing approach.
IP-based restoration algorithm for optical networks
Mianfeng Lin, Chunbo Mu, Laifu Fang, et al.
One distributed restoration algorithm used to protect optical transport networks against network failures is proposed in the paper. The algorithm takes advantage of the existing IP protocols, and therefore it can restore the affected traffic in the distributed and efficiently manner. By carrying the wavelength availability information in protocol data unit, the algorithm can reserve the required capacities as well as search the restoration routing.
Optimization of protection domains for a survivable optical network with short leap shared protection (SLSP)
Survivability and continuity of service to the end users during the occurrence of failure have evolved to be a critical issue in the aspect of control and management of the next-generation Internet. The ordinary path-based and link-based shared protection schemes can only provide a limited spectrum of protection services with coarse protection granularity, which will not be able to satisfy the versatile requirements of multimedia applications on the Internet in the foreseeable future. In this paper we propose a framework, Short Leap Shared Protection (SLSP), for service-guaranteed end-to-end shared protection for the optical Internet. We will describe the algorithm for implementing this idea in detail and show that SLSP enhances the 1:N and M:N shared protection schemes in terms of scalability, flexibility and class of service.
Protection scheme in NSFCNET
Xiaodong Jia, Yi Dong, Jianping Wang, et al.
Protection and restoration issues in optical networks especially DWDM networks are attracting significant attention for future high-capacity transport applications. In this paper a flexible protection scheme of BWLSR/2 (Two-fiber Bi-directional Wavelength Line Switched Ring)/1/ is demonstrated, this protection system can function automatically without the interference of the network management system. In the case of fiber broken or single channel transport problem it can protect the optical signal. It is implemented successfully in the NSFCNET.
Optical Flow and Label Switching
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Optical flow networking: a new approach for IP over DWDM services
Jon Anderson
This paper describes a new architecture for providing a full range of IP services and features in the optical layer. This architecture, called optical flow networking (OFN), uses a new class of device that tightly integrates IP routing and reconfigurable WDM. OFN enables new networking capabilities in four key areas: IP over (lambda) provisioning and routing; flow-based QoS optical packet services; IP/(lambda) traffic engineering and differentiated IP/(lambda) service resiliency. With these capabilities, the OFN IP-optical integrated architecture provides key advantages over the conventional, multi-element overlay approach by enabling intelligent QoS IP/(lambda) networking with overall simplified network operations. Therefore, it is a viable solution for next generation metropolitan IP-based services.
Optical networks with deflected MPLS paths
Stig Nygaard Quist, David Kennedy Hunter, Derek J. Stagg, et al.
In this paper, we introduce deflection routing for irregular meshed networks in an optical packet based environment. By using the MPLS (Multiprotocol Label Switching) control plane to manage the deflected paths, we offer a relatively simple way of controlling the otherwise complicated deflected paths. This is beneficial due to the way it simplifies the optical packet switch so it only needs to deal with simple forwarding and thereby relaxing the need for buffering. The latter is becoming increasingly more important in optical networks since there is no practical optical memory insight for the near future. By introducing deflection routing along with statistical wavelength multiplexing, the need for buffers is greatly reduced while the network resources are better utilized. MPLS is emerging as a main protocol for future networks, whether being based on packet switched or circuit switched technology, hence rendering this approach to be compatible with most modern and future systems.
Statistical multiplexing in optical flow switching networks
Kai Wu, QingJi Zeng
In IP over WDM networks, optical paths (OP's) form a virtual topology seen from the upper IP layer, and greatly relieve the burden of electronic processing thanks to optical bypasses. However, in contrast to the circuit-switching, connection-oriented and coarser OP's, the IP is packet-switching, connectionless and finely granular in nature. Special care should be taken in the control plane to bridge the gap. In our research, we incorporate the idea of optical flow. Optical flows are optically switched in intermediate nodes and converted into electronic form at termination to treat small nested flows. Two modes of optical flow switching (OFS) are examined. One is optical burst switching (OBS), which sends control packet ahead of data to announce a switching and make future reservations. The other is Optical Grooming Switching (OGS), which put packet flows into finer container with discrete yet flexible bit rate. We find that both of these two modes use statistical multiplexing to bridge the gap between IP packets and WDM OP's, and such function is fulfilled respectively by scheduling in OBS and by framing in OGS. Taking snapshots of statistical multiplexing, we formulate the bandwidth distribution (BWD) of the whole OFS networks and the bandwidth usage (BWU) over each node pair. The BWD can be expressed by the product of a traffic-independent grooming matrix with the traffic demand matrix under a given virtual topology. Changes to the grooming matrix are reflected by adjustments in framing or scheduling. Three distinct states of BWU are also identified to determine the initiation of such changes. The BWU states are hence proposed to add to the extension of existing routing protocols.
Performance of the optical label eraser based on Lyot-Sagnac filter
Zhensheng Jia, Minghua Chen, Kun Xu, et al.
This paper presents a novel label eraser that has the flat passband based on the Lyot-Sagnac filter for all optical label swapping (AOLS) networks. The cascaded performance of this filter is analyzed. The cascaded performance of the fiber-loop mirror (FLM) filter is also analyzed to bring into comparison with the Lyot-Sagnac filter. It is shown that power penalty of 1.48dB through four cascaded Lyot-Sagnac filters is obtained obviously prior to it of FLM filters that is 5.62dB. Meanwhile, the influences of the residual labels on the intermediate swapping node labels through the filters are also investigated, it is seen that the power penalty is only less 1dB when the optical power ratio of residual label to the new label signal arrives at - 8 dB.
Implementation Issues II
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All-optical MAN based on IP
Shuwen Yang, Maoguo Cai, Junxian Ma, et al.
A novel MAN (Metro Area Network) based on IP technology and all-optical network technology is presented in this paper. The information infrastructure network platform of Shenzhen, which is an all-optical IP Metro Area Network (MAN) with Tb/s capability, is proposed. The architecture of the all- optical MAN, core network and access network is given.
Versatile emulator for automatically switched optical networks
Bernd Stilling, Martin Nathansen
Development, testing and deployment of routing and signaling protocols for automatically switched optical networks (ASON) are considerably simplified by using an emulation tool. In this paper we present an emulator that supports OSPF routing and (G)MPLS based signaling. Currently the emulator supports the signaling protocol CR-LDP but we are working on the integration of RSVP-TE. Running complete protocol stacks for each emulated node enables the emulator to fill the gap between a network simulation and a real network. To allow the emulation of very large networks which can not be done on a single workstation the network can be emulated using a set of workstation. By adding additional workstations the number of emulated nodes is almost unlimited. The architecture and the functionality of the emulator are described and an example of an emulation is given. The example network with 16 nodes is investigated regarding the behavior in case of network failures.
Novel method to suppress waveform distortion and compress frequency chirp in SOAs as in-line amplifiers in WDM networks
Wenshan Cai, Yi Dong, Mingyuan Zou, et al.
A novel method to suppress the waveform distortion and compress frequency chirp in SOAs as in-line amplifiers in WDM networks is proposed and experimented. The results show that the signal distortion and pattern effect are reduced significantly and over 5dB expansion of input dynamic range is achieved.
Operation model study of optical Internet with MP[lambda]S
Mingye Jin, Lemin Li
The MP (lambda) S is proposed to implement IP running over the WDM layer. However it's just a beginning work. In order to integrate MPLS with WDM transmission layer deeper, we borrow the definition that mapping label with optical lightpath, and further propose a flexible MP (lambda) S operation model that use MPLS as the control plane in WDM network and then integrate IP with WDM. This model extends the mapping from one-layer mapping into four-layer mapping. Further analysis about mapping method of each layer and a function model of such four-layer mapping are given.
10-Gb/s optical Internet network with 16-channel bidirectional DWDM transmission system
Jianping Wang, Yi Dong, Minyu Yao, et al.
10Gb/s optical internet network (NSFCnet) in china with protection switching function and performance monitoring is introduced in this paper. 16x10Gb/s Transmission is demonstrated over 400km SMF with 3 network elements consisting of multiplxers and demultiplxers. The power penalties for all 16 channels are measured to be less than 2dB (BER=10-10).
Poster Session
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Integrated routing in wavelength-routed all-optical networks
Xudong Yang, QingJi Zeng, Xu Zhu, et al.
All-optical wavelength division multiplexing (WDM) networks using wavelength routing technology are considered to be a potential and practical solution to the next generation of wide area backbone networks. The ever-increasing demand for bandwidth further enhances the application of WDM optical networking technology. The main problem involved in design and optimization of wavelength-routed optical network is lightpath routing and wavelength assignment, namely, R&WA. In previous work on the R&WA problem, the project function has been analyzed by mathematic tools, such as integrate linear programming (ILP), heuristic algorithms or probability model, under the assumption of an ideal physical layer over which transmission impairments are ignored. In practical application, however, such impairments and their influence over traffic performance should be considered seriously, and the lightpath selection should be adjusted accordingly. In this paper, we propose an integrated approach for lightpath routing, which considers both the limitations of network topology and resource and the restrictions resulted from transmission impairments through the path computed by our heuristic algorithm when performing lightpath routing. The selected paths resulted from our proposed R&WA algorithm will be evaluated in a coarse-to-fine mechanism. By analyzing the impact of the optical devices (OXC, EDFA etc.) deployed through the lightpath, an optimal path is finally determined. This paper is composed mainly in three parts. For the first part, as to a given network topology, we present the ligthpath routing result, which investigate the influence of different network parameters, based on the proposed heuristic algorithm combining graph theory. For the second part, we studied the impact of various transmission impairments over BER performance, including crosstalk and noise caused by the optical devices. For the third part we combine the results obtained from the former two parts, and evaluate the selected path in a coarse-to-fine mechanism to make an optimal selection. The problem of load balancing is also briefly discussed in our paper.
Traffic grooming in interconnected multigranularity WDM SDH/SONET rings
Jie Xu, QingJi Zeng, Yun Wang, et al.
All-optical wavelength division multiplexing (WDM) networks using wavelength routing technology are considered to be a potential and practical solution to the next generation of wide area backbone networks. The ever-increasing demand for bandwidth further enhances the application of WDM optical networking technology. The main problem involved in design and optimization of wavelength-routed optical network is lightpath routing and wavelength assignment, namely, R&WA. In previous work on the R&WA problem, the project function has been analyzed by mathematic tools, such as integrate linear programming (ILP), heuristic algorithms or probability model, under the assumption of an ideal physical layer over which transmission impairments are ignored. In practical application, however, such impairments and their influence over traffic performance should be considered seriously, and the lightpath selection should be adjusted accordingly. In this paper, we propose an integrated approach for lightpath routing, which considers both the limitations of network topology and resource and the restrictions resulted from transmission impairments through the path computed by our heuristic algorithm when performing lightpath routing. The selected paths resulted from our proposed R&WA algorithm will be evaluated in a coarse-to-fine mechanism. By analyzing the impact of the optical devices (OXC, EDFA etc.) deployed through the lightpath, an optimal path is finally determined. This paper is composed mainly in three parts. For the first part, as to a given network topology, we present the ligthpath routing result, which investigate the influence of different network parameters, based on the proposed heuristic algorithm combining graph theory. For the second part, we studied the impact of various transmission impairments over BER performance, including crosstalk and noise caused by the optical devices. For the third part we combine the results obtained from the former two parts, and evaluate the selected path in a coarse-to-fine mechanism to make an optimal selection. The problem of load balancing is also briefly discussed in our paper.
Unified control plane scheme for IP over WDM
Yun Wang, QingJi Zeng, Jie Xu, et al.
The development of advanced optical networking technology put forward a requirement for a new control plane to implement such functionalities as resource discovery, state information dissemination, path selection, and path management. In this paper, the development and evolution of optical networks are analyzed at first, then the requirements for the unified control plane are put forward, finally, the functional modules and interface properties for the unified control plane are investigated in detail.
Enhanced restoration approach in IP-centric mesh optical networks
Jimin Liu, QingJi Zeng, Jun Huang, et al.
Optical layer networking and survivability are very important branches of the study of optical communication network. Recent standards proposals have focused on extending MPLS protocols to manage optical network resources. These proposals have concentrated on provisioning optical connections and offering restoration capability in mesh optical networks. Few papers, however, are concentrated on protection issues of backup path. By considering the protection of backup path, survivability of protection scheme will improve. This article presents a novel paradigm enhancing the existing pre-established protection schemes using Multi-Protocol Lambda Switching architecture and demonstrates local restoration and global restoration for backup path with examples. Finally, we discuss the advantages of this approach and present future work.
Optical multicast using a mixed waveband forwarding in MPL(ambda)S network
Dae-gun Kim, Kyung-Young Kang, Joosang Yoon, et al.
Optical multicast in a MPL(ambda)S network has not yet to be defined. An MPL(ambda)S network consists of lambda switching devices such as OXC. In this paper, optical multicast using the mixed waveband forwarding within a MPL(ambda)S network is discussed on both dense-mode and sparse-mode. And the OXC capable waveband switching is suggested. Unlike unicast routing, dense-mode multicast routing trees are established in a traffic-driven manner and it is not possible to topologically aggregate such trees, which are rooted at different sources. In sparse-mode multicast, source-specific trees may coexist with a core/shared trees, and it is not possible to assign a common wavelength label to traffic from different sources on a branch of the shared tree. This paper suggests a mixed waveband-forwarding scheme for supporting all two types of multicast (shared tree, source tree) routing trees in a MPL(ambda)S network.
Offset time decision (OTD) algorithm for guaranteeing the requested QoS of high priority traffic in OBS networks
Won-Ho So, Yun-Ho Cha, Sun-Sik Roh, et al.
In this paper, we propose the Offset Time Decision (OTD) algorithm for supporting the QoS in optical networks based on Optical Burst Switching (OBS), which is the new switching paradigm, and evaluate the performance of the OTD algorithm. The proposed algorithm can decide a reasonable offset time to guarantee the Burst Loss Rate (BLR) of high priority traffic by considering traffic load of network and the number of wavelengths. In order to design this effective OTD algorithm, firstly we illustrate the new burst loss formula, which includes the effect of offset time of high priority class. As the decision of offset time corresponding to the requested BLR, however, should use the reversed formula of new one, we are not able to use it without any changes. Thus, we define the Heuristic Loss Formula (HLF) that is based on the new burst loss formula and the proportional equation considering its characteristics. Finally we show the OTD algorithm to decide the reasonable offset time by using HLF. The simulation result shows that the requested BLR of high priority traffic is guaranteed under various traffic load.
Novel approach for assigning wavelengths in WDM all-optical networks (AONs)
Debashis Saha, Amitava Mukherjee, Sahadeb Jana, et al.
In this paper, we present an algorithm for effectively assigning wavelengths to ligthpaths in a multihop WDM optical network wherein the physical medium consists of optical fiber segments, which interconnect wavelength selective optical switches. This physical medium permits a limited number of wavelengths to be re-used among various fiber links, thereby offering vary high aggregate capacity. The proposed algorithm is a one where the problem of wavelength assignment in WDM optical network is posed as a graph-coloring problem. In this algorithm, an auxiliary graph is used, which is constructed from a given input physical topology and ligthpaths requests of a network. On this auxiliary graph a dynamic coloring approach assigns permanent colors to nodes. The number of colors needed represents the number of wavelengths required for the network. The algorithm is tested on a traffic model, and the coloring and timing efficiency are studied through extensive simulation and compared with the existing wavelength assignment heuristic algorithm. We find, that for a wide range of lightpath requests, the performance of our proposed algorithm is performing well as compared with the existing algorithm.
Promising network evolution technology: MPLS
Peng Xu, Wang Yu, Wei Ding
This paper presents Multi-Protocol Label Switch (MPLS) as a promising network evolution technology to implement the transition from traditional ATM and IP network to the next generation optical Internet. As bandwidth-intensive services increase, and as the number of users connected to the Internet grows, traditional ATM and IP network, though with their own advantages, could hardly satisfy the ever-increasing requirements. Under such conditions, the network evolution is impending. MPLS, which integrates the control of IP routing on the layer 3 with the simplicity of Layer 2 switching, inheriting their advantages, and discarding their disadvantages, is deem as the most promising candidate for the network evolution technology. Furthermore, the recent research on MPLS traffic engineering provides an ideal solution to combine MPLS control plane with optical switching, and even to incorporate DWDM multiplexing capabilities in IP routers. The perspective of MPLS is further illustrated.
Standardization efforts in optical networking focused on architecture and signaling issues
Soo-Hyun Choi, Tae-Man Han, You-Hyeon Jeong
This paper summarizes the present state of optical networking, whereabouts of the optical network by which IP-centric networks carry the traffic. By start out from the assuming that the Internet transport infrastructure is moving towards a model of high speed routers interconnected by optical core networks, various technical issues mainly on optical network architecture and signaling standardization trends are presented in this article. Also, the author present the concepts of generalized multiprotocol label switching (GMPLS) in accordance to the future direction of deploying the IP over optical networks.
Laser source providing multiple ITU wavelengths for WDM applications
Lin Xue, Huafeng Zhao, Shan Huang
A novel Fiber Bragg Grating (FBG) external cavity laser diode capable of providing multiple ITU wavelengths is presented. An air gap Fabry-Perot filter with transmission peaks on ITU wavelengths was inserted in the external cavity. While the FBG wavelength was tuned to a F-P transmission peak by the simple beam, the laser source generated an ITU wavelength. In our experiment 7 ITU wavelengths was acquired. As a versatile wavelength generating system, developed for both high precision wavelength calibration and stabilization of tunable diode lasers, our laser source already considerably improved the quality of our diode laser spectra and is promising for WDM communication systems.
GMPLS-based hierarchical optical routing switching architecture
Wei Wei, QingJi Zeng
With the development of Generalized Multi-Protocol Label Switching (GMPLS: an optical extension to traditional Multi-Protocol Label Switching) by IETF, we envision that today's static optical networks will evolve towards dynamic optical networks with a intelligent, flexible and scalable control plane software. In this paper we firstly describes a novel IP-Centric optical network architecture called Hierarchical Optical Routing Switching Architecture (HORSA) based on GMPLS--a flexible, highly scalable IP over WDM optical network architecture for the delivery of public network IP services. Two kinds of node including Optical Core Router (OCR) and Optical Edge Router (OER) are involved in this optical network architecture. In this section we also discuss some issues such as routing, signaling and management of HORSA. Secondly, we mainly focus on the design issues of OCR and OER including multi-granularity switching fabrics, intelligent OTU, control plane software and etc. Finally, we reach conclusions that HORSA based on GMPLS is suitable for current hybrid network environment and optimistic for IP traffic transfer, it can be scaled to pure optical IP over WDM architecture based on Optical Packet Switch (OPS).
Section
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Intelligentization: an efficient means to get more from optical networking
Zhi Yun Chen
Infocom is a term used to describe the merger of Information and Communications and is used to show the radical changes in today's network traffic. The continuous growth of Infocom traffic, especially that of Internet, is driving Infocom networks to expand rapidly. To service providers, the traffic is consuming the bandwidth of their network. Simultaneously, users are complaining too slow, the net never stopped in China. It is the reality faced by both the service providers and equipment vendors. Demands from both the customers and competition in market call for an efficient network infrastructure. What should a Service Provider do? This paper will first analyze the development trends of optical networking and the formation of the concepts of Intelligent Optical Network (ION) and Automatic Switched Optical Network (ASON) as a solution to this problem. Next it will look at the ways to bring intelligence into optical networks, discussing the benefits to service providers by showing some application examples. Finally, it concludes that the development of optical networking has arrived at a point of introducing intelligence into optical networks. The intelligent optical networks and Automatic Switched Optical Networks will immediately bring a wide range of benefit to service providers, equipment vendors, and, of course, the end users.