Generalized Multiprotocol Label Switching Research Articles

A vertical Path Computation Element (PCE) based path provisioning scheme in multilayer optical networks

The explosive growth of Internet traffic has led to a dramatic increase in demand for data transmission capacity, which requires high transmission rates beyond the conventional transmission capability. This demand has spurred tremendous research activities in new high-speed transmission and switching technologies. As optical transmission technology keeps maturing, next generation optical networks are expected to be controlled by Generalized Multiprotocol Label Switching (GMPLS) protocol suite and operating at multiple switching layers. In order to ensure the most efficient utilization of multilayer network resources, and to maximize revenue from existing capacity, effective global provisioning solution that providing the network with the possibility of reacting in advance to traffic changes should be provided. This paper proposes a new path provisioning scheme in multilayer optical networks based on the vertical Path Computation Element (PCE) architecture to efficiently exploit multiple PCE cooperation. This paper also investigated the problem of how network nodes overcome limited visibility of network resources. Unlike most of the previous studies, the topology of the upper switching layer is not always equal to the physical topology of lower switching layer.

Energy Efficiency in the Future Internet: The Role of Optical Packet Switching and Optical-Label Switching

This paper reviews the energy efficiency of optical-packet-switching (OPS) systems in comparison with electronic packet switching and hybrid packet switching in the context of future networks. The paper will first discuss the energy efficiency metrics that should include considerations for life-cycle analysis, applications, and network-wide goodput. The state-of-the-art electronic packet switching router is currently energy-limited in scalability as it is difficult to implement a router with more than 1 MW power consumption. The OPS router that imitates electronic router's store-and-forward schemes is expected to suffer poor energy efficiency due to the complexity in the high-speed control plane necessary to control many optical buffer stages. The hybrid optical router achieves easier buffer management but its energy efficiency is still limited by the store-and-forward approach. The OPS router based on all-optical contention resolution without relying on store-and-forward method can keep the control plane very simple and achieve very high energy efficiency. Network-wide performance and energy efficiency in the context of generalized multiprotocol label switching (GMPLS)- and multiprotocol label switching (MPLS)-based networking are also discussed.

Bandwidth Squeezed Restoration in Spectrum-Sliced Elastic Optical Path Networks (SLICE)

With the continuing growth in the amount of backbone traffic, improving the cost-effectiveness and ensuring survivability of the underlying optical networks are very important problems facing network service providers today. In this paper, we propose a bandwidth squeezed restoration (BSR) scheme in our recently proposed spectrum-sliced elastic optical path network (SLICE). The proposed BSR takes advantage of elastic bandwidth variation in the optical paths of SLICE. It enables spectrally efficient and highly survivable network recovery for best-effort traffic as well as bandwidth guaranteed traffic, while satisfying the service level specifications required from the client layer networks. We discuss the necessary interworking architectures between the optical path layer and client layer in the BSR in SLICE. We also present a control framework that achieves flexible bandwidth assignment as well as BSR of optical paths in SLICE. Finally, we describe an implementation example of a control plane using generalized multi-protocol label switching (GMPLS).

Distributed Protocol for Removal of Loop Backs with Asymmetric Digraph Using GMPLS in P-Cycle Based Optical Networks

Pre-configured protection cycles (p-cycles) have drawn many attentions due to the fully pre-connected cyclic structures, ring-like speed, mesh-like spare capacity efficiencies and fast switching characteristics. In this paper, we propose a novel removal of loop back (RLB) approach with standard protocol extension (the flooding based distributed cycle pre-configuration (F-DCPC)) to solve the resource inefficiency issue due to long restored paths for symmetric dynamic networks. Meanwhile, distributed cycle pre-configuration (DCPC) is a representative technique for automatic p-cycle configuration. But for the mesh network topology under asymmetric service distribution, it works especially with more network convergence time and larger amount of extra controlling overhead. So in our RLB approach, F-DCPC scheme using generalized multi-protocol label switching (GMPLS) protocol to solve the problems of configurations and reconfigurations with asymmetric digraph in high-speed optical mesh networks is presented. Additionally, to describe the basic idea of traffic splitting strategy in the unidirectional resource distribution, we present the mathematic model with a heuristic algorithm to accelerate resource configuration. We evaluate the performance of F-DCPC utilizing proposed RLB approach with various classical p-cycles enumeration algorithms and allocation strategies by experimental simulations implemented in OPNET modeler, and the simulation results show the effectiveness of the proposed scheme.

Multi-layer network architecture in support of end-to-end transparent optical connectivities

In order to effectively accommodate a wide variety of emerging and future applications with diverse requirements, an intelligent optical network capable of the rapid and resilient delivery of on-demand transparent transmission capacity is required. This paper investigates a multi-layer network architecture where a generalized multiple protocol label switching (GMPLS) controlled transparent wavelength switched optical network (WSON), as the transport core, collaborates with multiple client optical burst switching (OBS) networks distributed at the edge. Dynamic interworking mechanism as well as the related signaling/routing protocol extensions for multi-QoS burst streams transmission among different OBS domains are proposed so as to provision an end-to-end (e2e) transparent optical connectivity with on-demand bandwidth to end-users. Moreover, the survivability of this transparent optical connectivity is also addressed. To validate the feasibility of this architecture, an integrated OBS/WSON network testbed was constructed, and stable e2e transparent connectivities were successfully demonstrated for an efficient multi-QoS burst streams transmission.

网状光网络中基于信令的路径段保护方法

Path protections have become increasingly important for current mesh optical networks because fast restorations in generalized multiprotocol label switching (GMPLS) networks are uncertain. However, setting up additional disjoint paths to protect connections leads to more path setup blocking and signaling collisions. We analyze signaling collisions, path blocking and blocking probability, as well as calculate node-to-node blocking probabilities. A signaling-based path-segment protection (PSP) is proposed, which integrates segment protections and path protections as well as enhances the performance of path protections and ring protections. The setup of PSP connections causes less blocking probability than the setup of path protection connections in the simulations.

Solving GMPLS Multi-Region Path Constraints

In this letter, we propose a novel binary integer program (BIP) to obtain the optimal and correct combination of switch type per link, and adaptation capabilities per node, along a multi-region traffic engineered label switched path (TE-LSP) in a generalized multiprotocol label switching (GMPLS) network. The proposed BIP considers constraints such as the nesting/un-nesting order of LSPs, the adaptation capacity per node, the bandwidth capacity per link, as well as efficiency. By efficiency constraint we refer to opting primarily for nesting/un-nesting as opposed to conversion which is a resource demanding process. Numerical results show that applying the proposed BIP in a constraint shortest path first (CSPF) algorithm achieves lower blockage rates and outperforms an existing graph transformation method which is the closest related work to our proposal.

Experimental Performance of Shared Path Protection With Flooded Versus Collected Sharing Resource Information in GMPLS WSON Networks

In generalized multiprotocol label switching (GMPLS)-enabled wavelength-switched optical networks (WSONs), shared path protection (SPP) attains 100% survivability with an acceptable recovery time, for lightpaths affected by a single-link failure. This is achieved by sharing backup resources. Nevertheless, neither the standard OSPF-TE nor the RSVP-TE protocols support the respective flooding/collection of shareable resource information for SPP purposes. This prevents the source node from computing backup paths exploiting the SPP advantages, and the destination node from performing optimal wavelength assignment (WA) favoring the reuse of shareable resources. In this paper, we experimentally evaluate, in the GMPLS control plane of the ADRENALINE testbed, the performance improvements when shareable resource information is either flooded (by enhanced OSPF-TE) and/or collected (by enhanced RSVP-TE), under the wavelength continuity constraint. Additionally, we propose efficient SPP path computation and WA algorithms, considering three information dissemination strategies: aggregated unreserved bandwidth, aggregated shared bandwidth, and wavelength-channel granularity.

Towards the realistic planning of GMPLS-based optical transport networks

The multi-granular switching concept defined in Generalized Multiprotocol Label Switching (GMPLS) is expected to be a future-proof solution for mitigating the Optical Crossconnet scalability problems associated with the skyrocketing growth of traffic in optical transport networks. In this paper, we address the problem of planning the GMPLS-based (or multi-granular) transport network with color (or label) conversion and signal regeneration capabilities. The objective of the problem is to minimize the total weighted port count in the transport network. The novelty of this problem lies in the incorporation of the following for the first time: (1) considering all traffic granularities defined in GMPLS; (2) allowing wavelength, waveband, and fiber conversions; (3) considering the optical-reach limitation of optical signals; and (4) customizing the optical reach of all-optical paths. Due to the computational complexity of the problem, we propose various efficient heuristics that are capable of solving large-sized problems in a reasonable amount of time. In order to achieve the best possible solution to the planning problem, a comprehensive evaluation of different heuristic variations through illustrative examples and simulations is conducted. The results also provide valuable insights into many issues that can contribute to further research and development in this area.

Analysis of crosstalk and modeling of possible number of routing stages for optically transparent wavelength-division multiplexing nodes of generalized multiprotocol label-switched networks

Crosstalk and power penalty analysis for optical code-switched static wavelength routing wavelength-division multiplexing nodes of a generalized multiprotocol label switched (GMPLS) network is presented. The performance of the system is analyzed for coherent crosstalk, end-to-end bit error rate, and the code length. We introduce a new approach to estimate the blocking probability in crosstalk-impaired GMPLS networks. Packet error rate is estimated for an increasing traffic condition. A well-known Erlang's traffic model is used to examine the performance of the system.

Integrated routing in GMPLS-based IP/WDM networks

The Internet traffic evolution has forced network operators to migrate toward an integrated infrastructure which brings the IP and optical layers under a unified model. The integration between the two technologies has been facilitated by the development of the Generalized Multi Protocol Label Switching. In the integrated scenario, Multilayer Traffic Engineering can be reinforced with integrated routing techniques. Integrated IP/WDM routing facilitates the routing decision phase by allowing a node to have a complete knowledge of the IP and WDM domains when accommodating traffic. This study focuses on integrated IP/WDM routing. We analyze two basic policies widely discussed in literature: one policy prioritizes the traffic accommodation on the virtual topology, while the other prioritizes the traffic accommodation on the physical topology. We show that both the mechanisms do not lead to efficient resource utilization because they tend to congest one layer more than the other one. We propose an adaptive heuristic which combines the advantages of both the policies. When accommodating traffic, the proposed approach selects the appropriate layer depending on the resource utilization being experienced in the virtual and the physical topologies. We demonstrate via simulations that the cross-layer resource optimization executed by the proposed scheme achieves significant improvements in terms of blocking ratio.

GMPLS-based Multidomain Restoration: Analysis, Strategies, Policies and Experimental Assessment

A connection spanning, for example, several countries crosses multiple optical backbone networks, each one controlled by different administrators or operators. In this context, the interworking of these networks is thus necessary to set up end-to-end optical connections. A key issue when delivering such optical services is the use of efficient and fast restoration strategies to recover a connection disruption. To this end, there are several issues and policies that a network operator should address, such as interdomain failure information exchange and the point of repair (PoR) placement problem. Upon a failure’s occurrence, exchanging interdomain failure information results is essential to attain both an efficient use of the network resources (i.e., wavelength channels) and a fast restoration time. In this regard, within the GMPLS (Generalized Multi-Protocol Label Switching) framework, interdomain information exchange remains unstandardized. Three network operator policies are proposed to yield different restoration mechanisms according to different interdomain failure exchanges. Additionally, three PoR strategies are pointed out and are qualitatively compared. Finally, selected policies and restoration strategies are experimentally validated and compared in terms of the restoration time. Experiments have been carried out over a multidomain optical network infrastructure connecting the GMPLS-based control planes of the UPC CARISMA and the CTTC ADRENALINE test beds.

Survivable routing algorithm with mixed shared protection in fault‐tolerant GMPLS multi‐layered optical networks

AbstractIn this paper, we studied survivability in general multi‐protocol label switching (GMPLS) multi‐layered optical networks and proposed a novel mixed shared protection algorithm (MSPA) based on the integrated layered graph (ILG) to tolerate single‐fibre link failure. The ILG is composed of one virtual topology layer (VTL), corresponding to IP/MPLS layer; multiple wavelength‐plane layers (WPLs), corresponding to the wavelength‐division multiplexing (WDM) optical layer; and some virtual links that connect the VTL to each WPL in order to solve the problem on routing, wavelength assignment and low‐speed traffic grooming. For every connection request, the MSPA first computes a single‐hop or multi‐hop label switching path (LSP) pair, involving a working LSP and a physical link‐disjoint backup LSP in the VTL. If the LSP pair is not found in the VTL, the MSPA computes the new LSP pair in the WPL. Conversely, if the new LSP pair is not detected in the WPL, the MSPA computes the hybrid multi‐hop LSP pair in the ILG. In the MSPA, if the two working LSPs are in physical link‐disjoint, their corresponding backup LSPs can share the backup bandwidth. In addition, the working LSPs and the backup LSPs can also share the same mixed of wavelength, in which the different bandwidths can be assigned to different working and backup LSPs. Simulation results show that, compared to previous algorithm, the MSPA can obtain a better bandwidth utilisation ratio (BUR) with a lower blocking probability. Copyright © 2010 John Wiley & Sons, Ltd.

Wavelength layer recovery in transparent optical networks

Ultra-high capacity transmission systems utilizing dynamic photonic switches enable transparent networking with reduced optoelectronic conversions and simplified and automated operations and maintenance. Due to recent advances in control functions for wavelength switching in optical networks, network service providers envision the same level of automated connection provisioning and restoration capabilities at the wavelength layer as offered by time division multiplexing (TDM) or packet switched networks. Implementing Generalized Multiprotocol Label Switching (GMPLS), transparent networks can offer a high level of reliability with automatic restoration as well as reduced resources compared to legacy 1 + 1 protection mechanisms. Based on preplanned path computation, selection, signaling, and allocation of optical resources, three recovery schemes are described in the context of the wavelength connections: protection, dynamic restoration, and a combination of protection and restoration. Through the use of network simulations, we analyze the impact of transparency constraints such as optical switch activation delay and sequential light path establishment on the recovery time. This analysis includes the trade-off between different recovery strategies and transmission system reach. é 2010 Alcatel-Lucent.

Extending next generation network (NGN) architecture for connection-oriented transport

Next Generation Network (NGN) is the architecture of the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T in short) supporting the provisioning of Quality of Service (QoS)-guaranteed services over different packet transport technologies. Such capability derives from the effectiveness of a dynamic resource control performed by the Resource Admission Control Function (RACF) at service set-up. Control Plane (CP)-enabled connection-oriented transport networks can guarantee the QoS support for new bandwidth-greedy NGN services across the optical transport segment thanks to the ability of automatic path set-up and traffic segregation. But the Internet Engineering Task Force (IETF) standard for the CP in transport networks, i.e., the Generalized Multi-Protocol Label Switching (GMPLS) is not yet included within the NGN supported transport technologies. In this work, we outline architectural guidelines and design strategies for ITU-T RACF employment across GMPLS-controlled networks while providing a viable solution for dynamic resource control that takes into account operational issues for the integration of GMPLS capabilities within NGN architecture (i.e., supported interfaces, actual node capabilities). An NGN prototype implementing the proposed architectural enhancement is also presented as a proof of concept. The prototype highlights how the extended ITU-T NGN can set-up Multimedia over IP (MoIP) services using GMPLS-controlled transport objects.

波长交换光网络中基于路径计算单元的冲突解决方案设计

A contention resolution scheme, P-cycle auto-switching (PCAS), is proposed in wavelength-switched optical networks (WSONs) based on generalized multi-protocol label switching (GMPLS) to solve backward blocking. This system permits the preferable request and switches the other to a backup path generated by the P-cycle. Simulation results show that the PCAS scheme is effective in mitigating backward blocking, especially under concentrated load.

Extending path computation element for lightpath restoration in wavelength-switched optical networks

Current generalized multi-protocol label switching (GMPLS) standards do not include adequate models for wavelength-switched optical networks (WSON) in recovery mechanisms. In this letter, GMPLS/path computation element (PCE) extensions are applied for the restoration of the lightpaths disrupted by collision or optical impairment. A reserved deection routing scheme is proposed to achieve fast restoration. It uses the expanded PCE component to compute and assign the backup paths for lightpath recovery. Numerical results demonstrate that this scheme is effective and low cost.

Service differentiation in IP/MPLS over ASON/GMPLS networks

There is a general agreement that the future infrastructure for broadband communications will consist of Automatically Switched Optical Networks (ASONs) controlled by the Generalized Multi-Protocol Label Switching (GMPLS) control plane. Due to the convergence of most services on the Internet Protocol (IP) layer, ASON/GMPLS networks need to provide transport for a variety of applications having different Quality of Service (QoS) requirements. This implies that the Differentiated Service paradigm, which improves the QoS in pure IP networks, needs to be extended to the new underlying infrastructure. This article proposes and compares three schemes for the service differentiation in IP/MPLS over ASON/GMPLS networks. Simulation results demonstrate that a fair trade-off between QoS and resource utilization is achieved when combining routing policy differentiation (RPD), virtual topology differentiation (VTD), and virtual topology sharing (VTS) techniques. The RPD technique decides on the multilayer routing policy to apply depending on the Class of Service (CoS). The VTD technique transports different CoS over different independent virtual topologies. The VTS technique introduces a certain degree of resource sharing among the different virtual topologies.

An analytical model for GMPLS control plane resilience quantification

This paper concentrates on the resilience of the generalized multi-protocol label switching (GMPLS) enabled control plane. To this end, the problem of control plane resilience in GMPLS-controlled networks is firstly stated and previous work on the topic reviewed. Next, analytical formulae to quantify the resilience of generic meshed control plane topologies are derived. The resulting model is validated by simulation results on several reference network scenarios.

Spare capacity reprovisioning for high availability shared backup path protection connections

Shared backup path protection (SBPP) has been widely studied in the Generalized MPLS (GMPLS) networks due to its efficient spare capacity sharing as well as simplicity and flexibility in service provisioning. This paper presents a novel availability evaluation strategy for the end-to-end (E2E) availability of an SBPP connection by considering up to two simultaneous failures, where the sequence of failures in a failure pattern is considered. To minimize the redundancy while meeting the E2E availability requirement, partial restoration is defined and embedded in the developed model, by which a novel parameter, called a protection level, is manipulated. Based on the proposed availability model, two Linear Program (LP) formulations are introduced, which aim to perform spare capacity reprovisioning along each link for dynamic allocation of SBPP connections under either failure-dependent or failure-independent policies. Extensive simulations are conducted to validate the proposed availability model and demonstrate the effectiveness of the spare capacity reprovisioning architecture. The proposed availability-aware spare capacity reprovisioning approaches are then implemented on top of a well known survivable routing scheme – Successive Survivable Routing (SSR), where the spare capacity saving ratio is taken as the performance measure. We will show that the proposed spare capacity reprovisioning framework is an effective approach for achieving the GMPLS-based recovery in packet-switched networks.