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The leakage of confidential information is one of important issues in the network security area. Elastic Optical Networks (EON) as a promising technology in the optical transport network is under threat from eavesdropping attacks. It is a great demand to support confidential information service (CIS) and design efficient security strategy against the eavesdropping attacks. In this paper, we propose a solution to cope with the eavesdropping attacks in routing and spectrum allocation. Firstly, we introduce probability theory to describe eavesdropping issue and achieve awareness of eavesdropping attacks. Then we propose an eavesdropping-aware routing and spectrum allocation (ES-RSA) algorithm to guarantee information security. For further improving security and network performance, we employ multi-flow virtual concatenation (MFVC) and propose an eavesdropping-aware MFVC-based secure routing and spectrum allocation (MES-RSA) algorithm. The presented simulation results show that the proposed two RSA algorithms can both achieve greater security against the eavesdropping attacks and MES-RSA can also improve the network performance efficiently.

Spatial division multiplexing enabled elastic optical networks (SDM-EONs) are the potential implementation form of future optical transport networks, because it can curve the physical limitation of achievable transmission capacity in single-mode fiber and single-core fiber. However, spectrum fragmentation issue becomes more serious in SDM-EONs compared with simple elastic optical networks (EONs) with single mode fiber or single core fiber. In this paper, multi-core virtual concatenation (MCVC) scheme is first proposed considering inter-core crosstalk to solve the spectrum fragmentation issue in SDM-EONs. Simulation results show that the proposed MCVC scheme can achieve better performance compared with the baseline scheme, i.e., single-core virtual concatenation (SCVC) scheme, in terms of blocking probability and spectrum utilization.

A novel strategy is presented to operate a mixed fixed/flexible grid optical network which may be used to gradually migrate from a fixed to a flexible mode of operation. Routing and spectrum allocation (RSA) in an optical network where fixed and flexible grids co-exist using a multi-path sub-band virtual concatenation (VCAT) or split spectrum (SS) technique is considered. Mixed integer linear programming models and an efficient heuristic algorithm based on spectrum window planes are proposed for the RSA optimization. The results obtained for the static traffic demand indicate that it is operationally more convenient to use the multi-path VCAT only by itself in a mixed grid optical network to guarantee performance comparable to that of the joint multi-path and single-path VCAT case. Network performance is also evaluated in terms of bandwidth blocking probability (BBP) under a dynamic traffic demand. Simulation results show that the multi-path VCAT scheme can efficiently utilize the overall spectrum resources with low blocking. The results of studies with both static and dynamic traffic demands also confirm that migration from a pure fixed grid optical network to a pure flexible grid will be desirable for better network capacity utilization.

The elastic optical network (EON) provides fine-grained and orthogonal frequency slots for establishing the connection that will realize high-rate data transmission among data centers (DCs). With the implementation of cloud DCs (CDCs) and EON virtualization, achieving EON embedding (EONE) is essential, which includes two components: node mapping from the virtual machine to the CDC and link mapping from the virtual lightpath to fiber link(s). In particular, the link mapping must satisfy some rigid constraints in terms of spectrum continuity, consistency, and nonoverlapping, which may create spectrum fragments over fiber links. Thus, in this paper, we reoptimize the virtual concatenation (VCAT) framework accompanied by the hitless push-pull spectrum movement (PPSM) function when the common link mapping fails. Our design framework integrates spectrum movement with inverse multiplexing such that more EONE requests can be satisfied by performing effective spectrum defragmentation. We also optimize the number of subbands with a constrained buffer size to compensate the differential delay at the receiving end. The problem is formulated using the relaxed integer linear programming (ILP) model, and the corresponding heuristic tailored to four different service-sorting strategies is also designed. The simulation results verify the superiority of our method in terms of increasing the spectrum efficiency and reducing the blocking rate of EONE requests. This paper is the first work to focus on designing a reoptimized VCAT framework accompanied by the hitless PPSM function for the EONE that includes both node and link mapping processes rather than a simple spectrum defragmentation.

Sub-band virtual concatenation (VCAT) technique can help improve spectrum utilization of an elastic optical network (EON). On the other hand, availability is an important service level agreement (SLA) criterion for an optical transport network. This paper evaluates how the sub-band VCAT technique can enhance the availability of an EON. A quadratic programming optimization model and an efficient heuristic algorithm are developed to maximize availability-weighted network bandwidth. Also, an allowed maximal differential delay (MDD) between different sub-paths that make up a VCAT connection is considered as a constraint, and the related availability-weighted network bandwidth is evaluated. Considering the limited spectrum capacity of each transponder, we also extend the model to assign spectra based on each independent transponder. Simulation results show that the sub-band VCAT technique can significantly increase average network availability of an EON compared to the case without VCAT (non-VCAT). A trend is also observed that with an increasing MDD, the average network availability increases, but saturates for a large MDD. In addition, the limitation of the available transponders at each node can become a bottleneck for provisioning the bandwidth between node pairs.

Spatial division multiplexing elastic optical networks (SDM-EONs) will become the most important form of future optical transport networks, because it can break the physical limit of achievable capacity in single-mode and single-core fibre. However, spectrum fragmentation issue becomes more serious in SDM-EONs compared with in single EON. Crosstalk-aware cross-core virtual concatenation (CCVC) scheme is first proposed to solve the spectrum fragmentation issue in SDM-EONs. Simulation results show that CCVC can achieve lower blocking probability and higher spectrum utilisation compared with single-core virtual concatenation scheme.

A dynamic Optical Transport Network (OTN) has the advantage of being able to adjust the connection capacity on demand in order to respond to variations on traffic patterns or to network failures. This feature has the potential to reduce operational costs and at the same time to optimize networks resources. Virtual Concatenation (VCAT) and Link Capacity Adjustment Scheme (LCAS) are two techniques that when properly combined can be used to provide improved dynamism in OTN networks. These techniques have been previously standardized in the context of Next Generation SDH/SONET networks. VCAT is used to tailor the capacity of network connections according to service requirements, while LCAS can adjust dynamically that capacity in a hitless manner. This paper presents an overview of the application of VCAT/LCAS techniques in the context of OTN. It explains in detail how these techniques can be employed to resize the connection capacity and analyses its use in network protection solutions. Furthermore, a detailed analysis of the time delays associated with different operations is provided and its application to some reference networks is undertaken. The obtained results provide an idea about the time delays of the capacity adjustment processes and define potential scenarios for implementing VCAT/LCAS techniques.

We present a novel strategy for the operation of a mixed fixed/flexible grid optical network which would be useful for the gradual migration from a fixed to a flexible mode of operation. Routing and spectrum allocation (RSA) in co-existing fixed/flexible grid optical networks with a multi-path sub-band virtual concatenation (VCAT) technique is considered. An integer linear programming (ILP) model and efficient heuristic algorithms based on k-shortest path (KSP) and spectrum window planes (SWPs) are proposed for the RSA optimization which minimizes the maximum number of frequency slots (FSs) used in the fiber link. Simulation studies are presented to show the efficiency of the proposed approaches.

An investigation on researches of technologies and applications tailored to optical-connection cloud data center networks (OCDCNs) is made in this article, moreover, the existing approaches of virtual network embedding (VNE) and future challenges are summarized for OCDCNs. Also, we propose a promising VNE solution in OCDCNs integrating both elastic optical networks and virtual concatenation technology.

Next generation synchronous digital hierarchy is a popular transport technology for integrated voice and data communication. It typically uses virtual concatenation (VCAT) for dynamic bandwidth management. This paper discusses different issues related to VCAT. Paper mainly focuses on the differential delay that occurs as all the VCAT members traverse through different path to reach the destination. These streams do not reach the destination at the same time and thus incur differential delay. Buffers are provided at the receiver to compensate for differential delay. The larger the differential delay, the larger is the buffer requirement at the receiver. Differential delay/buffer size can be reduced by proper routing of the traffic. In the existing receiver circuits, all incoming streams are allocated the same buffer space, specifying the maximum differential delay it can compensate. This results in a large buffer requirement. To overcome this limitation, this paper proposes a novel scheme of allocating buffers dynamically to all the streams. To achieve this, differential delay between the streams is computed by extracting the multiframe indicator and then as per the delay, each stream is allocated buffer space from a common buffer pool. The common buffer pool consists of a number of buffer modules. The size of each module is equal to the frame size for the specific virtual channel, and the size of the common buffer pool is architecture dependent. Sixty per cent reduction in the buffer requirement is predicted using this scheme, at the receiver. For functional verification of the concept, a hardware circuit is designed. Copyright © 2011 John Wiley & Sons, Ltd.

Cross Virtual Concatenation is the new technique proposed for bandwidth efficient transmission of data over SDH networks. SDH networks came into existence for reliable voice transmission. As the demand of data traffic grew in wide area networks, new technologies were developed and standardized for data transmission over SDH networks. The technologies used namely, GFP (generic framing procedure), VCAT (virtual concatenation) and LCAS (link capacity adjustment scheme) enable network operator to provide integrated voice and data services over their legacy SDH infrastructure. Data packets are encapsulated using framing protocols GFP. VCAT is a process of distributing the GFP framed data payload in number of virtual channels of same capacity forming a Virtually Concatenated Group (VCG). LCAS is used for dynamic bandwidth allocation. LCAS enhances the VCAT scheme with hitless in service addition and removal of VC's to/from the VCG.VCAT combines homogeneous virtual channels together which in some cases limits the performance of VCAT. This paper describes the implementation of new concatenation technology named cross virtual concatenation (CVC), which combines heterogeneous VC's together to utilize the SDH bandwidth more efficiently. CVC implementation requires only end node equipments to be upgraded as VCG members travel through the link similar to the conventional VCAT. This paper proposes FPGA implementation of transmitter and receiver circuits for 100 Mbps Ethernet data transmission over next Generation SDH systems using CVC, where two types of VC's namely VC-3 and VC-12 are used for data transmission. Total Transmission delay is calculated as 125 μs. There is no complexity added at the receiver side due to this delay. The receiver is designed for 32 ms differential delay compensation which can be increased up to maximum 256 ms by increasing the buffer size at the receiver.

Ethernet-over-SONET/SDH (EoS) is a popular approach for interconnecting geographically distant Ethernet segments using a SONET/SDH transport infrastructure. It typically uses virtual concatenation (VC) for dynamic bandwidth management. The aggregate SONET/SDH bandwidth for a given EoS connection is obtained by “concatenating” a number of equal-capacity virtual channels. Together, these virtual channels form a virtually concatenated group (VCG). In this article, we introduce a new concatenation technique, referred to as cross-virtual concatenation (CVC), which involves the concatenation of virtual channels of heterogeneous capacities. We show that CVC can be implemented through a simple upgrade at the end node, thus utilizing the existing legacy SDH infrastructure. By employing CVC for EoS systems, we show that the SDH bandwidth can be harvested more efficiently than in conventional VC. We consider two problems associated with routing CVC connections: the connection establishment problem and the connection upgrade problem. The goal of the first problem is to compute a set of paths between two EoS end systems such that a total bandwidth demand and a constraint on the differential delay between the paths are satisfied. Among all feasible sets, the one that consumes the least amount of network bandwidth is selected. For this problem, we develop an integer linear program (ILP) and an efficient algorithm based on the sliding-window approach. For the connection upgrade problem, the goal is to augment an existing set of paths so as to increase the aggregate bandwidth, while continue to meet the differential-delay constraint. We model this problem as a flow-maximization problem with a constraint on the delay of the virtual channels with positive flow. We then consider the problem of path selection under imprecise network state information. Simulations are conducted to demonstrate the advantages of employing CVC and to evaluate the performance of the proposed algorithms.

SONET/SDH is historically the dominant telecom transport infrastructure for backbone networks, and it is optimized for reliable delivery of voice and private-line services. Efficient utilization of the existing infrastructure through novel methods and algorithms can lead to higher revenue, which is attractive for network operators. In this study, we examine a network of inter-connected SONET/SDH rings that use dual-node interconnection employing the drop-and-continue facility, which is the de-facto standard for interworking SONET/SDH protection architectures. We develop an efficient algorithm for provisioning in such a network while keeping fragmentation of capacity low and taking into account the various constraints imposed by the underlying physical layer. We examine the case of dual-node-interconnected ring networks employing both contiguous and virtual concatenation (a next-generation SONET/SDH architecture), and as expected, we discover that provisioning higher-bandwidth connections with virtual concatenation offers significant improvement. The stringent time-slot alignment and contiguity constraints imposed by contiguous concatenation are further compounded by the constraints imposed by the ring interworking architecture, and virtual concatenation allows capacity to be used more efficiently.

The next-generation SONET metro network is evolving into a service-rich infrastructure. At the edge of such a network, multiservice provisioning platforms (MSPPs) provide efficient data mapping enabled by Generic Framing Procedure (GFP) and Virtual Concatenation (VC). The core of the network tends to be a meshed architecture equipped with Multi-service Switches (MSSs). In the context of these emerging technologies, we propose a load-balancing spare capacity reallocation approach to improve network utilization in the next-generation SONET metro networks. Using our approach, carriers can postpone network upgrades, resulting in increased revenue with reduced capital expenditures (CAPEX). For the first time, we consider the spare capacity reallocation problem from a capacity upgrade and network planning perspective. Our approach can operate in the context of shared-path protection (with backup multiplexing) because it reallocates spare capacity without disrupting working services. Unlike previous spare capacity reallocation approaches which aim at minimizing total spare capacity, our load-balancing approach minimizes the network load vector (NLV), which is a novel metric that reflects the network load distribution. Because NLV takes into consideration both uniform and non-uniform link capacity distribution, our approach can benefit both uniform and non-uniform networks. We develop a greedy load-balancing spare capacity reallocation (GLB-SCR) heuristic algorithm to implement this approach. Our experimental results show that GLB-SCR outperforms a previously proposed algorithm (SSR) in terms of established connection capacity and total network capacity in both uniform and non-uniform networks.

This article describes how bandwidth virtualization can enable transmission of ultra-high bandwidth 40 Gb/s and 100 Gb/s services over existing optical transport networks independently of the underlying network infrastructure. An overview of the technology alternatives available to enable high-bandwidth service transport is provided, along with a discussion of the relative merits of different approaches. The authors describe how wavelength division multiplexing, using large- scale photonic integrated circuits combined with the use of a digital virtual concatenation mapping protocol, can be used to enable decoupling of 40 Gb/s and 100 Gb/s service provisioning from the underlying optical link engineering, thereby enabling bandwidth virtualization. Real-world implementation examples of bandwidth virtualization are provided, including 40 Gb/s service transmission over a 2000-km fiber link with 65 ps of peak PMD, a field trial of 40 Gb/s service transmission over an 8477-km trans-oceanic network, and finally a field trial of a pre-standard 100 gigabit Ethernet service transmission over a 4000-km terrestrial long-haul network.

We investigate reliable multipath provisioning of traffic in high-capacity backbone mesh networks, e.g., next-generation SONET/SDH networks supporting virtual concatenation (VCAT). VCAT enables a connection to be inversely multiplexed on to multiple paths, a feature that may lead to significantly improved performance over conventional single-path provisioning. Other mesh networks such as those employing optical wavelength-division multiplexing (WDM) and multiprotocol label switching (MPLS) can also benefit from this multipath provisioning approach. We propose effective multipath bandwidth as the metric to provision a connection while satisfying its reliability requirements (measured in terms of availability). We demonstrate that effective multipath bandwidth provides more flexibility and lower blocking probability without the cost and the complexity associated with traditional protection schemes developed for optical WDM and MPLS networks. We also investigate the practical problem of provisioning effective multipath bandwidth with cost constraints. We analyze the tractability of the problem and present a heuristic which results in significantly reduced number of blocked connections due to cost constraints.

The elastic optical network (EON) provides fine-grained and orthogonal spectrum slots for the establishment of the elastic connection using orthogonal frequency division multiplexing (OFDM). Currently, the EON interconnection has realized the high-rate transmission among data centers (DCs). With the implementation of cloud DCs (CDCs) and EON virtualization, it becomes very essential to achieve the elastic network embedding (ENE) that facilitates the resource sharing in inter-cloud-data-center networks. The ENE operation consists of two components, the virtual-node mapping from virtual machine to CDC and the virtual-link (VL) mapping from virtual lightpath to fiber link(s). Thus an ENE request can be satisfied only when those two mapping processes have completed successfully. But during the VL mapping, some rigid constraints must be satisfied, such as the spectrum continuity, etc. This makes the ENE operation create the spectrum fragments over fiber links, which results in the denial of requests. Thus in this paper, we take the virtual concatenation (VC) into account when the VL mapping fails. The problem is formulated using the relaxed integer linear programming (ILP) model, and we also design a VC-based heuristic. Simulation results have verified the superiorities of the VC scheme on increasing the spectrum utilization and reducing the blocking rate of ENE requests.

The optical virtual concatenation (OVC) function of The Terabit LAN was demonstrated for the first time at the iGrid 2005 workshop in San Diego, California. The TERAbit-LAN establishes a lambda group path (LGP) for an application where the number of lambdas/L2 connections in a LGP can be specified by the application. Each LGP is logically treated as one end-to-end optical path, so during parallel transport, the LGP channels have no relative latency deviation. However, optical path diversity (e.g. restoration) can cause LGP relative latency deviations and negatively affect quality of service. OVC hardware developed by NTT compensates for relative latency deviations to achieve a virtual bulk transport for the Electronic Visualization Laboratory's (EVL) Scalable Adaptive Graphics Environment application.

Rapid advances in next-generation SONET/ SDH and optical switching technologies along with dynamic generalized multi-protocol label switching control architectures have enabled many new service provisioning paradigms. In particular, a key addition is the new virtual concatenation feature that allows for inverse multiplexing of connection demands across SONET/SDH domains. This paper presents a novel tiered survivability scheme that leverages this feature to support multiple levels of service survivability and higher load carrying capability and service resiliency. Detailed simulation performance analysis results are also presented along with conclusions and directions for future work.

We consider the problem of minimizing the differential delay in a virtually concatenated Ethernet-over-SONET (EoS) system by suitable path selection. In such a system, a service provider can dynamically add virtual channels to or drop them from a Virtually Concatenated Group (VCG). A new virtual channel can be added to the VCG provided that the differential delays between the new channel and the existing ones are within a certain limit that reflects the available memory buffer of the EoS system. We model the problem of finding such a virtual channel as a constrained path selection problem, where the delay of the required (feasible) path is constrained not only by an upper bound but also by a lower bound. We consider two cases: exactly known link delays and imprecisely known link delays. For the first case, we propose two algorithms for finding a feasible path. The first is based on a link metric that linearly combines the original link weight (the link delay) and its inverse. The theoretical properties of such a metric are studied and used to develop a highly efficient heuristic for path selection. The second algorithm is a "backward-forward" heuristic in which the nodes in the graph are prelabeled during the backward phase. The labels are then used in the forward phase to identify a feasible path. For the imprecise-link-state case, the problem is modeled as one of finding the most probable feasible path, where link weights are random variables. A "backward-forward" heuristic is proposed which again uses prelabeling of the graph in the backward direction followed by a forward search that attempts to minimize an objective function. Simulations are conducted to evaluate the performance of the proposed algorithms and to demonstrate the advantages of the probabilistic path selection approach over the classic trigger-based approach.

Demand for Ethernet services is increasing exponentially worldwide. Improvements such as generic framing procedure (GFP) and virtual concatenation (VCAT) have been introduced, increasing the efficiency of synchronous optical network/synchronous digital hierarchy (SONET/SDH) transport for packet traffic. The growing volume of packet traffic necessitates further refinement of transport networking techniques toward a more packet-centric model that incorporates increased efficiency in handling packet traffic, and more packet-friendly optical networks; for example, multiprotocol label switching (MPLS) and generalized multiprotocol label switching (GMPLS) enabled networks. The most effective next-generation of multi-service provisioning platforms (MSPPs) must account for these realities and provide a solution for both bandwidth utilization and management capabilities while constituting a platform that can scale from last-mile access to metro core networks. These platforms should incorporate packet-based technologies including MPLS to provide a flexible and cost-effective mix of multi-service traffic engineering and encapsulation techniques, quality of service (QoS), security, and resiliency to providers competing in an increasingly packet-centric market. This paper explains how new transport systems are using novel architectures and exploiting new technologies to support emerging applications with network architectures best suited to the changing characteristics of the traffic they are required to carry.

Optical control planes came to the forefront during the Internet boom of the late 1990s as the network operations solution of choice for emerging mesh architectures. However, in spite of the numerous advantages, their deployments in service provider networks have been below expectations. While the telecom downturn of the last few years is often blamed, we also posit that control planes lost some of their luster because the applications they were primarily marketed for — rapid provisioning for bandwidth-on-demand services and mesh restoration — failed to get the requisite traction in the marketplace. In this paper, we propose that the changed landscape notwithstanding, optical control planes still fulfill a critical role in the service provider network. We argue that an underlying control plane foundation, with its routing and signaling infrastructure, gives tremendous flexibility to the operator to build new value-added services that can significantly improve network efficiency. Consequently, once deployed, these novel services can provide alternate avenues for revenue and capital expenditure (CapEx) savings in the long term. To that end, we present two applications — link defragmentation for legacy traffic and Ethernet mesh restoration — that leverage virtual concatenation in next-generation synchronous optical network (SONET) standards. We highlight our implementation experiences and show that the underlying control plane infrastructure is key to a low overhead deployment. We quantify the savings and conclude that in the current environment, these new customizable value-added services provide a prudent strategy for increasing service provider traction, especially with respect to long-term CapEx savings.

Next-generation SONET/SDH technologies--namely, generic framing procedure, virtual concatenation, and link-capacity-adjustment scheme--enable network operators to provide integrated data and voice services over their legacy SONET/SDH infrastructure to generate new revenue. An important open research problem on data over SONET/SDH (DoS) is survivability: SONET automatic protection switching is too resource inefficient for data services, and the protection mechanisms of data networks are too slow for mission-critical applications.We propose two approaches for provisioning survivable DoS connections. Our approaches exploit the tradeoff between resource overbuild and fault-recovery time while utilizing the inverse-multiplexing capability of virtual concatenation to increase backup sharing. Our results show that one approach achieves low resource overbuild and much faster fault recovery than that of data networks, and the other approach achieves fast fault recovery comparable to SONET 50-ms protection (for typical U.S. backbone networks) while still achieving modest backup sharing. We further investigate the tradeoff between network blocking performance and network control and management complexity resulting from the number of paths M a connection can be inversely multiplexed onto: larger M leads to more freedom in routing and better network performance but increases network control and management complexity. Our results indicate that the network blocking performance for small values of M (e.g., M = 2 for some representative backbone network topologies) is almost as good as the case in which M is infinity.

Optical/packet convergence is the process that merges optical transport infrastructure and data networking capabilities. In this paper, we discuss the process, its drivers, and the impact of this convergence on network management systems and overall network operations. We identify the business problem in terms of the challenges to the evolution of network operations. Specifically, we address next-generation transport networks, which have adapted well to the key requirements of packet networking through techniques such as Virtual Concatenation, Generic Framing Procedure, Integrated Ethernet switching, and the Generalized Multiprotocol Label Switching (GMPLS) control plane. We also address the wider issue of operations support consolidation across different data networks including integration utilizing a Multiprotocol Label Switching (MPLS) core. We consider the different customer environments for which convergence will need operations support system (OSS) solutions and discuss various options that can lead to a viable operations plan. We close the paper with our preliminary recommendations for how operational convergence can be achieved for different network operations processes.

The new techniques, link capacity adjustment scheme (LCAS) and virtual concatenation not only make SDH/SONET networks accommodate the data service efficiently, but also provide a high-layer protection for client services, under which no spare capacity needs to be reserved for protection and the service transmission continues unless all concatenated links have failed. In this paper, we analyse the performance of this kind of protection in ring topology and mesh topology respectively. The results show that the time-to-transmission halt for the first time exceeding 1 year can reach 99.999%, if the number of the independent concatenated links is greater than two. In addition, the protection performance is analysed in detail given the granted maximal decrease ratio of the service transmission bandwidth. Copyright © 2005 AEIT.

The Optical Internetworking Forum (OIF) conducted a world interoperability demonstration in conjunction with SUPERCOMM held in Chicago June 22-24, 2004. The demonstration was executed on a global stage with seven carriers across three continents internetworking through an intelligent control plane in a multivendor environment of 15 vendor participants. OIF's demonstration successfully included dynamic end-to-end connection management between client devices and transport network elements in a multidomain, multinode environment. The global connectivity included network elements (NEs) that incorporated the OIF optical user-to-network interface (UNI) and external network-to-network interfaces (E-NNI) among various vendors. Furthermore, carriers were able to test the new Ethernet over synchronous optical network/synchronous digital hierarchy (SONET/SDH) capabilities utilizing the generic framing procedure (GFP-F), virtual concatenation (VCAT), and the link capacity adjustment scheme (LCAS), based on International Telecommunication Union - Telecommunication Standardization Sector (ITU-T) recommendations. This article described the technical approach and execution of this demonstration.

This paper explores the feasibility of deploying optical burst switching (OBS) in metropolitan area networks (MANs) as an alternative to synchronous optical network (SONET), over wavelength-division multiplexing. We present a comparison between two OBS architectures (with centralized and distributed scheduling schemes), SONET, and next-generation SONET (NG-SONET), respectively. We quantify some of the performance metrics such as end-to-end delay and loss rate when supporting Ethernet traffic in metro ring networks. Our simulation results show that OBS offers significant performance improvement over SONET and NG-SONET. In general, the OBS architecture with distributed scheduling has a superior delay performance, whereas the OBS architecture with centralized scheduling has a better loss metric.

This paper describes the applications and value of a new type of multi-service switch (MSS) for SONET/SDH metro networks. Metro networks are ultimately responsible for connectivity to end customers and, as such, are key in defining new services that build on those already deployed. Metro networks, with their embedded base of SONET/SDH rings, will be the key to services success. New intelligent services in the wholesale domain (e.g., services sold to service providers) and in the retail domain (e.g., services sold to end customers) must be delivered at lower operational and capital costs, which implies an evolution of the architectural design of the metro network. Network elements that are deployed in the metro networks to serve the need for “traditional” wideband and broadband services must be especially friendly to new services that build on the Internet protocol (IP) suite. Network elements fulfilling these needs are MSSs such as Lucent Technologies' LambdaUnite® MSS, which can be integrated into emerging data networks, and can consolidate embedded SONET/SDH rings, enable migration to generalized multiprotocol label switching (GMPLS) mesh networks, offer very flexible Ethernet and Gigabit Ethernet data services, and support low-order grooming (VC-12 and VT1.5). MSSs can work cooperatively with multi-service provisioning platforms (MSPPs). Using the generic framing procedure (GFP) and high-order virtual concatenation (HO-VC), new service interfaces which emulate the behavior of wavelengths, can be adapted into the SONET/SDH network through the deployment of edge adaptation (e.g., line cards). © 2003 Lucent Technologies Inc.

Single-chip SDH/SONET framer architectures are described that permit data aggregation from several line ports. After presenting an overview of the usual parallel approach and an extension thereof that exploits distributed algorithms, we introduce a novel data-multiplexing architecture that should be suitable for accommodating data from a relatively large number of ports in a single device. In combination with the new virtual concatenation feature of SDH/SONET, this architecture should also allow transport of data from high-bandwidth applications over multiple wavelengths or multiple fibers.

Orthogonal Frequency Division Multiplexing (OFDM) has recently been proposed as a modulation technique for optical networks due to its higher spectral efficiency and superior impairment tolerance. There have been extensive studies on routing and spectrum assignment (RSA) of the OFDM-based elastic optical network, of which most focus on a single route for each lightpath service. In this paper, we study the RSA problem for the elastic optical network considering the multi-path subband virtual concatenation (VCAT) technique that allows the sub-bands of a VCAT lightpath connection to be transmitted over different routes. We develop integer linear programing (ILP) models to optimally solve the problem. We evaluate the benefit of the multi-path sub-band VCAT technique for the RSA problem through comparing with the non-VCAT case. In addition, because of the limitation of synchronization in the sub-band VCAT technique, we set a maximal distance difference among the sub-band paths of a VCAT connection to evaluate how the limitation can impact the RSA performance. We find that the multi-path sub-band VCAT technique shows a stronger benefit in a network with a higher nodal degree.

Virtual concatenation (VCAT) is a standardized layer 1 inverse multiplexing technique that can be applied to the optical transport network (OTN), synchronous optical network (SONET), synchronous digital hierarchy (SDH), and plesiochronous digital hierarchy (PDH) component signals. By inverse multiplexing, it combines multiple links at a particular layer into aggregate links to achieve a commensurate increase in available bandwidth on the aggregate link. While any inverse multiplexing scheme is about "more bandwidth", the VCAT/LCAS is a general technique that can enable a fairly broad range of network features such as (1) right sizing bandwidth for data applications, (2) bandwidth extraction from a mesh network, (3), bandwidth on demand and IP traffic engineering, and (4) provides new forms of protection-restoration and graceful degradation. In this paper, the authors have given a quick overview of VCAT/LCAS technology and just a few examples of its applications

The general frame size in an IEEE 802.11 wireless LAN environment is often much smaller than the specified MTU size. The small size of the frames increases the MAC layer traffic and can cause degradation in network performance. In this paper, we propose new IP packet concatenation methods that are able to merge two or more IP packets with same destination addresses into a MPDU. Our method provides a continuous monitoring of the channel state. If there are IP packets that can be concatenated, the concatenation is carried out at the same time as the channels are allocated to other nodes. At the receiving end, the data size of the received MPDU and the total length field in the IP header are compared to determine whether the received frame is concatenated or not. Our proposed method avoids any packet concatenation delay. When MAC layer traffic is low, our method provides a similar performance to existing wireless LANs. Our method can also improve the transmission performance as an increase in MAC layer traffic results in a decrease in the total traffic.

Providing the survivability in optical networks over wavelength-division multiplexing (WDM) is a critical concern. The design issue on WDM network is to minimize the buffer size and providing survivability based on differential delay and Multipath provisioning with the support of Virtual Concatenation (VC). In this paper, we propose the Shared Protection of the Largest Individual Traversed link (SPLIT) for survivable multipath and MFI (Multiframe Indicator) Buffer to reduce the buffer requirement at the receiver end of the VC with the help of minimized differential delay.

The elastic optical networking has become a promising solution of allocating continuous frequency slots according to spectrum demand. A provident spectrum defragmentation is presented through virtual concatenation, and it outperforms conventional push-pull methods by simulations.

Wavelength-division multiplexing (WDM) enables multiple communication links to use a common transmission fiber by transmitting a multitude of different wavelengths at the same time. This chapter describes WDM technology, including options such as coarse and dense WDM defined by standards such as ITU-T Recommendations G.652 to G.657. The wavelength spectrum allocation for the L-, C-, S-, E-, and O-bands is discussed. Related technologies, such as time-division multiplexing and erbium-doped fiber amplifiers, are also described in this context. Topics include service mapping using the generic framing procedure and virtual concatenation, technology for optical transceivers and filters, reconfigurable optical add/drop multiplexers, fiber Bragg gratings, and array waveguides. WDM link budgets and noise sources are also discussed, including rings and other topologies, protection schemes, dispersion compensating fiber, equalization, and modulation options including extensions to 100G.

We propose a resilient provisioning scheme for multi-flow elastic optical networking by exploiting elastic traffic assignment and path diversity. Our scheme requires no link-disjoint routing, and significantly reduces resource overbuild from Virtual Concatenation in two sample core networks.

We present a multi-flow virtual concatenation model in flexible spectrum networks. A split-multi-flow RSA algorithm (SMF) triggered by path cascading degree is proposed based on the model. Simulation results show SMF can get better performance.

Synchronous Digital Hierarchy (SDH) networks are wildly deployed by telecom service providers (SP) around the world. Conventionally, SDH network circuits have to be designed and provisioned beforehand. Circuit profiles, including capacity, circuit route, end points…, have to be assigned before service activations. Any attempt of network re-configuration caused by network failures or traffic congestions will lead to uncertain service interruption. To further increase network availability, SPs have to overbuild their networks or to assign backup route(s) for each critical circuit, which, however, is costly and inefficient. With the introduction of technologies such as Virtual Concatenation (VCAT) and Link Capacity Adjustment Scheme (LCAS) of Next generation SDH (NG-SDH), SPs are able to adjust their SDH circuits at various bandwidth granularities and to hitlessly increase or decrease bandwidth of each circuit. In this study, we propose an effective approach to locate overbuild bandwidth, failed circuits, as well as congested circuits based on real time traffic flow data and network alarm message. Then our approach reallocates overbuilt network bandwidth in responding to network failures or traffic congestions by exploiting the benefit of VCAT and LCAS. Our simulation results show that our approach can significantly improve network availability as well as network resource utilization with minimal cost.