Demonstration of the highly reliable Hikari router network based on a newly developed disjoint path selection scheme

Integration of multiprotocol label switching functions and multiprotocol lambda switching functions can enhance the throughput of IP networks and remove bottlenecks that are derived from electrical packet processing. To enhance the packet forwarding capability, NTT proposed a photonic MPLS concept that includes MP/spl lambda/S, and demonstrated IP, MPLS, and photonic MPLS integrated router systems called the photonic MPLS router. This router system is now called the Hikari router. The word Hikari is Japanese meaning beam, light, lightwave, optical, photonic, and sunshine. The amount of IP data traffic has grown remarkably. Massive IP routers and flexible route control mechanisms are now required to cope with the increased amount of traffic. The Hikari router can offer two solutions utilizing photonic switching technologies, and photonic network operation and management technologies. The first solution is utilizing photonic switching technologies realized using optical-switch-based crossconnect systems. The other solution is realized using the MPLS and MP/spl lambda/S signaling protocol and photonic network protection functions. In this article we report on the implementation of the Hikari router systems, propose a newly developed disjoint path selection scheme for generalized MPLS networks with shared risk link group constraints, and demonstrate the signaling protocol and network protection functions. The demonstration system achieves a distributed optical path set-up/tear-down protocol with an extended constraint-based routing label distribution protocol. Fast self-healing through automatic protection switching and a new restoration scheme are also implemented. These functions are successfully implemented, and the performance is verified on a demonstration network. The protection switching scheme achieves protection in less than 20 ms, and the optical path restoration scheme achieves restoration in less than 500 ms.     

Protection approaches for dynamic traffic in IP/MPLS-over-WDM networks

Due to the explosive growth of data-related traffic driven by the Internet, network reliability becomes an important issue. We investigate various protection approaches to handle failures for dynamic traffic demands in IP/MPLS-over-WDM networks. An LSP can be protected at either the IP/MPLS layer or the optical layer. In IP/MPLS layer protection, an LSP is protected by providing a link-disjoint backup LSP between its end nodes. In optical layer protection, an LSP is protected by the backup lightpath of each lightpath traversed by the LSP. We present two integrated routing algorithms: hop-based integrated routing algorithm and bandwidth-based integrated routing algorithm (BIRA) to set up the restorable bandwidth-guaranteed paths efficiently. Then we present a multilayer protection scheme for multiclass traffic in such networks. This scheme takes into account the different QoS and recovery requirements of the traffic to provide protection capability either at the MPLS layer or at the optical layer in a cost-effective manner. We use the connection blocking probability and number of optical-electrical-optical conversions as performance metrics to compare various protection approaches.     

Traffic grooming in WDM networks: past and future

Traffic grooming refers to techniques used to combine low-speed traffic streams onto high-speed wavelengths in order to minimize the networkwide cost in terms of line terminating equipment and/or electronic switching. Such techniques become increasingly important for emerging network technologies, including SONET/WDM rings and MPLS/MP/spl lambda/S backbones, for which traffic grooming is essential. In this article we formally define the traffic grooming problem, and we provide a general formulation that captures the features of a wide range of problem variants. We then present a comprehensive comparative survey of the literature that unveils the significant amount of research on this subject (the traffic grooming past). We also offer a broad set of ambitious research directions (the traffic grooming future) that are motivated by the exciting new challenges arising with the advent of MP/spl lambda/S technology.     

A concurrent two-layer restoration scheme for GMPLS WDM networks

Next generation backbone networks will likely consist of IP routers as well as optical cross connects (OXCs) and will deploy an optical control plane protocol. Generalized Multi Protocol Label Switching (GMPLS) has been proposed as the candidate of choice for the control plane. Optical fibers may carry large volumes of traffic and therefore adequate mechanisms must exist to enable the network to automatically recover from failures of fiber. In mission critical networks survivability becomes very important. We investigate the problem of autonomous recovery in such networks. The literature contains work in this area that investigates the problem of multilayer recovery. Such recovery had only been sequential in the sense that the published work recovers first in the optical domain, assuming the availability of redundant resources, and then proceeds to recover packet label switched paths. We report a recovery procedure for recovering packet label switch paths (packet LSPs) and lambda label switch paths (λLSP) concurrently. We have conducted an OPNET-based simulation study that compares the performance of the concurrent scheme with the previously published sequential two-layer recovery scheme. The study shows that the concurrent two-layer recovery scheme performs as much as forty-four percent faster than the sequential two-layer recovery scheme.     

Optical burst switching: a viable solution for terabit IP backbone

Wavelength-division multiplexing has emerged as an important physical layer technology. Optical transmission provides a physical layer capable of carrying bits at the speed at the order of a gigabit per second. Optical burst switching is proposed to overcome the shortcomings of conventional WDM deployment, such as lack of fine bandwidth granularity in wavelength routing and electronic speed bottlenecks in SONET/SDH. We describe an architecture for IP network over the OBS WDM transmission core. The use of MPLS-type technique for forwarding data bursts and the inclusion of a medium access control layer between the optical (WDM) and IP layers are the key ingredients of the proposed architecture. In particular, the architecture is based on provisioning MPLS paths, also called label switched paths, of desired quality of service through the OBS WDM transmission core. The MAC layer performs various OBS-specific functions, such as burst assembly, burst scheduling, and offset setting/traffic shaping. While burst assembly and burst scheduling are relatively straightforward, we point out that the offset setting strategy has significant impact on the performance of IP network operating over OBS WDM core. We describe a shaping scheme to set the offset, an important system parameter for OBS, between the successive data bursts of a given data stream (label switched path) and their associated control packets. This scheme results in robust operation of the network and also facilitates traffic engineering. Guidelines are provided for implementing various IP QoS mechanisms in the optical backbone using OBS.     

Topics in Optical Communications - Operational Evaluation of ASON/GMPLS Interdomain Capability over a JGN II Network Testbed

Traffic engineering in backbone networks is an important issue in supporting an appropriate QoS level to accommodate various types of traffic flows efficiently. Automatically switched optical networks and generalized multiprotocol label switching control planes are promising functionalities to achieve the sophisticated mechanism of interdomain traffic engineering. In this article we address dynamic operational scenarios to control IP traffic flows using the ASON/GMPLS control plane. This includes cut-through IP/MPLS routers and the rerouting of failed links through the tunnel of optical label-switched paths. This article presents an operational evaluation of traffic engineering. More specifically, we present QoS recovery for protecting high priority traffic using policy controllers and fault recovery of inter-domain LSPs over the JGN II network testbed. This article evaluates and discusses the feasibility of these operational scenarios using state-of-the-art optical switching and control- plane technologies.     

Differentiated Wavelength Assignment with QoS Recovery for DWDM Next Generation Internet Backbone Networks

This paper describes a differentiated wavelength assignment strategy for the appropriate allocation of wavelengths on wavelength-routed quality of service (QoS) routes with differentiated QoS class and recovery capabilities. The paper is based on the differentiated MPS services (DMS) model as a framework for optical bandwidth management and the real time provisioning of optical channels in re-configurable transport networks. MPS stands for multi protocol lambda switching which is a functional part of GMPLS (generalized MPLS). We discuss here a QoS recovery scheme at the optical layer, at the MPS layer, and at the IP layer, as related to QoS failure caused by device failures or attack-induced faults in dense-wavelength division multiplexing (DWDM) transport networks. According to the QoS characteristics of wavelength in optical links and the type of used optical cross-connect (OXC) nodes, a differentiated wavelength assignment strategy that considers QoS recovery capability is also described. We point out important problems that should be resolved in the DMS model for optical QoS routing with differentiated wavelength assignment.     

Two-layer mesh network optimization based on inter-layer decomposition

Presently, backbone data networks are converging toward a typical two-layer architecture of an IP/MPLS layer over an optical layer. In this paper, we study the problem of maximizing a utility function for an Internet service provider (ISP) of a two-layer mesh networks and propose an efficient decomposition method based on Lagrange relaxation. Differing from previous works on two-layer mesh networks, our proposed decomposition method decomposes an original two-layer mathematic optimization problem, respectively, into an IP/MPLS-layer and an optical-layer optimization problem by slacking the constraints between the two layers. This decomposition method enables to control the trade-off between running time and quality of the feasible solution. Numerical results for a variety of networks indicate that our proposed decomposition method is attractive to quickly find near optimal solutions.     

Optimized design of survivable MPLS over optical transport networks

In this paper we study different options for the survivability implementation in MPLS over Optical Transport Networks (OTNs) in terms of network resource usage and configuration cost. We investigate two approaches to the survivability deployment: single-layer survivability, where some recovery mechanism (e.g. protection or restoration) is implemented in a single network layer and multilayer survivability, where recovery is implemented in multiple network layers. The survivable MPLS over OTN design is implemented as a static network optimization problem and incorporates various methods for spare capacity allocation (SCA) to reroute disrupted traffic.The comparative analysis between the single layer and the multilayer survivability shows the influence of the traffic granularity on the survivability cost: for high-bandwidth LSPs, close to the optical channel capacity, the multilayer survivability outperforms the single layer one, whereas for low-bandwidth LSPs the single-layer survivability is more cost-efficient. For the multilayer survivability we demonstrate that by mapping efficiently the spare capacity of the MPLS layer onto the resources of the optical layer one can achieve up to 22% savings in the total configuration cost and up to 37% in the optical layer cost. Further savings (up to 9%) in the wavelength use can be obtained with the integrated approach to network configuration over the sequential one; however, this is at the increase in the optimization problem complexity. These results are based on a cost model with current technology pricing and were obtained for networks targeted to a nationwide coverage.     

An efficient mechanism for dynamic multicast traffic grooming in overlay IP/MPLS over WDM networks

This paper proposes an efficient overlay multicast provisioning (OMP) mechanism for dynamic multicast traffic grooming in overlay IP/MPLS over WDM networks. To facilitate request provisioning, OMP jointly utilizes a data learning (DL) scheme on the IP/MPLS layer for logical link cost estimation, and a lightpath fragmentation (LPF) based method on the WDM layer for improving resource sharing in grooming process. Extensive simulations are carried out to evaluate the performance of OMP mechanism under different traffic loads, with either limited or unlimited port resources. Simulation results demonstrate that OMP significantly outperforms the existing methods. To evaluate the respective influences of the DL scheme and the LPF method on OMP performance, provisioning mechanisms only utilizing either the IP/MPLS layer DL scheme or the WDM layer LPF method are also devised. Comparison results show that both DL and LPF methods help improve OMP blocking performance, and contribution from the DL scheme is more significant when the fixed routing and first-fit wavelength assignment (RWA) strategy is adopted on the WDM layer. Effects of a few other factors, including definition of connection cost to be reported by the WDM layer to the IP/MPLS layer and WDM-layer routing method, on OMP performance are also evaluated.     

IP over DWDM网络的生存性研究

探讨了IP over DWDM生存性的机制，研究了各个网络层的恢复特点以及不同层间相互作用对生存性的影响，明确了多层网络生存性的优点，从而得出光层能够提供最快的保护，较高的层能够提供智能恢复。最后提出了一种在光层的自动保护倒换的结构，这种保护能够优先考虑来自较高层的告警信息，使IP over DWDM网络做到智能化的快速恢复，为IP over DWDM网络的研究和建设提供了一定基础。     

A Pre-Segmented Sharing Recovery Scheme for MPLS/GMPLS

Path recovery aims at helping network operators automatically detecting and recovering from faults before human being’s intervening, and therefore can before customers notice these faults. By applying some algorithm of recovery, service provider (SP) can enhance the speed of repair and save paying refunds against broken service level agreement (SLA). Fast restoration of traffic after a network failure is a crucial aspect of current and future IP and transport networks. Recently, there is a…     

Convergence of Protection and Restoration in Telecommunication Networks

This paper argues for the need for convergence of protection and restoration schemes in today's telecommunication networks. Such networks are presented both in a layered context and from an end-to-end perspective. Such convergence is both necessary to ensure inter-working amongst a multitude of technologies deployed and desirable to ensure simplified operations. This paper further identifies the issues and inter-working items that need resolution in today's telecommunication and data networks in order to achieve inter working amongst various existing and emerging restoration and protection schemes in a layered and end-to-end context. End-to-end context covers the access, metro, and long haul dimensions of the network. It also encompasses both the services and the transport layers of the network in the context of multi-domain, multi service provider networks. Layering issues arise from the mix of technologies at several layers for example: optical transmission and CWDM/DWDM at physical layer, SONET/SDH framing and management at layer-1, ATM, MPLS, Ethernet, and resilient packet rings at layer-2, and finally IP and routing protocols at layer-3. Given that some degree of routing and signaling intelligence is migrating down to the optical layer equipment, this whole layering concept is currently in transition. This paper shows the need for convergence in the form of a two level protection and restoration scheme. A service independent layer and a mesh restoration capability at the routing layer.     

IP restoration vs. WDM protection: is there an optimal choice?

The exponentially growing number of Internet users armed with emerging multimedia Internet applications is continuously thirsty for more network capacity. Wavelength-division multiplexing networks that directly support IP-the so-called IP over WDM architecture-have the appropriate characteristics to quench this bandwidth thirst. As everyday life increasingly relies on telecommunication services, users become more and more demanding, and connection reliability is currently as critical as high capacity. Both IP and WDM layers can fulfil this need by providing various resilient schemes to protect users' traffic from disruptions due to network faults. This article first reviews the most common restoration and protection schemes available at the IP and WDM layers. These schemes may be present concurrently in the IP over WDM architecture, with the resilient mechanism of each connection specifically chosen as a function of the overall cost, application requirements, and management complexity. The article describes a versatile heuristic based on simulated annealing that may be adopted to optimize the concurrent use of IP restoration and WDM protection schemes in the same (mesh) network. The proposed heuristic allows varying the percentage of traffic protected by the WDM layer and that of traffic relying on IP restoration, taking into account topology constraints and network cost minimization. An additional feature of the proposed heuristic is the potential to trade solution optimality for computational time, thus yielding fast solutions in support of interactive design.     

IP over WDM光网分层体系结构

介绍了传统的 IP over WDM光网实现方案 ,指出各种方案的优缺点。阐述了 IP directly overWDM光网的分层结构实现方案 ,分析了各层功能 ,详细讨论了光层和光适配层。在指出分层结构实现方案的利弊后 ,讨论了波长标记和多协议波长交换方案。     

Efficient Distributed Bandwidth Management for MPLS Fast Reroute

As service providers move more applications to their IP/MPLS (multiple protocol label switching ) backbone networks, rapid restoration upon failure becomes more and more crucial. Recently MPLS fast reroute has attracted lots of attention as it was designed to meet the needs of real-time applications, such as voice over IP. MPLS fast reroute achieves rapid restoration by computing and signaling backup label switched path (LSP) tunnels in advance and re-directing traffic as close to failure point as possible. To provide a guarantee of bandwidth protection, extra bandwidth has to be reserved on backup paths. Using path merging technique as described in IETF RFC 4090 only, the network is able to share some bandwidth on common links among backup paths of the same service LSP, i.e., so-called intra-sharing. But no solution is provided on how to share bandwidth among backup paths of different service LSPs, i.e., so-called inter-sharing. In this paper, we provide an efficient distributed bandwidth management solution. This solution allows bandwidth sharing among backup paths of the same and different service LSPs, i.e., both intra-sharing and inter-sharing, with a guarantee of bandwidth protection for any single node/link failure. We also propose an efficient algorithm for backup path selection with the associated signaling extensions for additional information distribution and collection. To evaluate our schemes, we compare them via simulation with the basic MPLS fast reroute proposal, IETF RFC 4090, on two networks. Our simulation results show that using our bandwidth management scheme can significantly reduce restoration overbuild from about 250% to about 100%, and our optimized backup path selection can further reduce restoration overbuild to about 60%.     

IP/MPLS-Over-WDM网络的生存性

Internet的发展和数据业务的爆炸性增长对当前网络提出了更高的要求。网络将演变为IP/MPLS-over-WDM。对于这种以光网络为基础的网络构架,网络生存性问题变得尤为重要。由于以数据业务为中心的光网络至少包含IP层和光层,笔者提出了几个在多层网络生存性面临的问题,并给出了几种方案。最后,讨论了IP/MPLS--Over-WDM特有的生存性思考。     

Future transport network architectures

The architecture of today's long distance transmission networks, which we call the baseline architecture, is a complex and multilayered hierarchy of TDM circuits. One premise of the baseline architecture is that restoration from network failures is provided mostly by SONET/SDH rings. This article presents an alternative architecture that uses ATM and optical layer cross-connect technology for TDM services. Using a sophisticated set of network design tools developed at AT&T Labs-Research, we show that the alternative architecture offers dramatic capital savings and improved network efficiency over the baseline architecture. Most of this savings can be attributed to use of OLXC mesh network restoration, which makes more efficient use of capacity than SONET/SDH rings, and use of ATM switching for transport of TDM circuits, which consolidates the numerous TDM equipment layers inherent to the baseline architecture. In addition, motivated by the rapid growth of IP services, we analyze in the alternative architecture whether to provide restoration for IP services in the IP layer itself, by rerouting packets over precalculated restoration paths with MPLS, or to alternatively provide restoration of failed IP layer links in the OLXC layer. One potential advantage of IP layer restoration is that network operators may choose to only restore a fraction of the services, in particular the “priority” services, affected by a network failure. This article gives some methodology of how to determine this fraction at which IP layer restoration is cost-competitive with OLXC restoration     

A joint resilience scheme with interlayer backup resource sharing in IP over WDM networks

The survivability of IP over WDM networks gains importance as network traffic keeps growing. Recovery at the lowest layer is fast and scalable. However, it is usually considered to provide poor network utilization. In this article we propose a resilience scheme based on recovery at the lowest layer in which intralayer and interlayer backup resource sharing is utilized to improve the network utilization. By applying interlayer backup resource sharing, we can totally depend on the reserved backup resources for fiber link failures to guarantee 100 percent recovery of IP router failures. In addition, by applying intralayer backup resource sharing, the network utilization improvement of recovery at the lowest layer is much more significant than at the highest layer. Simulations results show that the proposed scheme can efficiently improve network utilization and be even more capacity-efficient than resilience schemes based on recovery at the highest layer.     

A path inflation control strategy for dynamic traffic grooming in IP/MPLS over WDM network

The use of alternate routes for traffic grooming in IP/MPLS over wavelength-division multiplexing (WDM) networks may lead to the propagation of congestion from one link to others in the IP/MPLS layer. This can be tackled by using the path inflation control (PIC) strategy proposed here for operating an IP/MPLS over WDM network in the overlay model. This supports dynamic traffic grooming with less blocking than other strategies. Network resource usage is also efficient as new lightpaths are set up for a new label switched path (LSP) request only when indicated by the congestion conditions.