Generalized Multiprotocol Label Switching Research Articles

Architecture, design, and modeling of the OPSnet asynchronous optical packet switching node

An all-optical packet-switched network supporting multiple services represents a long-term goal for network operators and service providers alike. The EPSRC-funded OPSnet project partnership addresses this issue from device through to network architecture perspectives with the key objective of the design, development, and demonstration of a fully operational asynchronous optical packet switch (OPS) suitable for 100 Gb/s dense-wavelength-division multiplexing (DWDM) operation. The OPS is built around a novel buffer and control architecture that has been shown to be highly flexible and to offer the promise of fair and consistent packet delivery at high load conditions with full support for quality of service (QoS) based on differentiated services over generalized multiprotocol label switching.

Multilayer traffic engineering for GMPLS-enabled networks

In recent years, significant work has been completed on traffic engineering enhancements to the generalized multiprotocol label switching protocol suite (E. Mannie Oct 2004) (D. Katz et al., Sept. 2003) (K. Kompella et al., Oct 2003). As a next step, reproducing the current trend of switching layers' integration happening in the data plane, network control is foreseen to go beyond the traditional per layer approach and tend toward an integrated model (K. Shimoto et al., Oct 2004) (E. Dotaro et al., Dec. 2004). In these multilayer environments, a single GMPLS control plane drives various distinct switching layers at the same time and as a coherent whole, taking benefit from the "common" property of GMPLS. Beyond this application of supporting network control across different technologies, in this article we catalog the unified traffic engineering paradigms, discuss their applicability, and present their enforcement techniques. Furthermore, we show that the common GMPLS concept has the advantage of low operational complexity, and enables unified TE capabilities such as efficient network resource usage and rapid service provisioning.

The role of management systems in optical/packet convergence

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.

High-Performance Hybrid-Switching Optical Router for IP over WDM Integration

Because pure electrical routers with their bandwidth limitations can hardly keep up with the tremendous traffic growth in the Internet, optical routers based on various optical switching techniques including optical wavelength switching (OWS), optical burst switching (OBS), and optical packet switching (OPS) have been suggested to cope with this problem. However, because OBS and OPS are both in their early experimental phase and OWS only provides coarse granularity switching, a hybrid-switching optical router with combined OWS and electrical packet switching is a necessity in order to accommodate the entire multi-granularity traffic with multi-service requirements in a cost-effective manner. Its coordination capability of optical circuit switching and electrical packet switching enables efficient/intelligent usage of network resources. In this paper, we first review research and developments of such IP routers employing optical switching/interconnection techniques and examine how these techniques can be used inside routers to scale node capacity and to improve optical Internet performance. We also present and study the performance of a terabit optical router with an optical-electrical hybrid-switching fabric. The node architecture is based on the idea of IP over WDM integration with Generalized Multi-Protocol Label Switching (GMPLS). The network-level performance evaluations show that the proposed hybrid-switching optical router is a cost-effective solution for building the next generation GMPLS-based multi-granularity optical Internet.

Design of Reliable IP/GMPLS Networks: An Integrated Approach

The increased bandwidth demand for new Internet applications suggests mapping IP directly over the wavelength-division multiplexing (WDM) layer. Since reliability is such a critical issue in these broadband networks, we propose an integrated design method which addresses the problem of survivability as viewed from the IP/MPLS layers but taking into account the failure mechanisms in the optical layer. This approach is becoming practical because of the emergence of generalized multiprotocol label switching (GMPLS) as a multilayer control plane that can support the signaling required for coordinating the restoration mechanisms in multiple layers. The model relies on network calculus to evaluate a quality of service (QoS) metric as actually perceived by end users and computes a preplanned restoration scheme to recover from failures. We discuss the numerical implementation, the convergence and the solutions produced by the algorithm and show that the resulting network can provide the prescribed QoS guarantees for all failure states.

Scalable Multi-Layer GMPLS Networks Based on Hierarchical Cloud-Routers

This paper proposes the hierarchical cloud-router network (HCRN) to overcome the scalability limit in a multi-layer generalized multi-protocol label switching (GMPLS) network. We define a group of nodes as a virtual node, called the cloud-router (CR). A CR consists of several nodes or lower-level CRs. A CR is modeled as a multiple switching capability (SC) node when it includes more than one kind of SC, which is fiber SC, lambda SC, time-division multiplexing (TDM) SC, packet SC, even if there are no actual multiple switching capability nodes in the CR. The CR advertises its abstracted CR internal structure, which is abstracted link state information inside the CR. A large-scale, multi-layer network can then achieve scalability by advertising the CR internal structure throughout the whole network. In this scheme, the ends of a link connecting two CRs are defined as interfaces of the CRs. We adopt the CR internal cost scheme between CR interfaces to abstract the network. This CR internal cost is advertised outside the CR via the interfaces. Our performance evaluation has shown that HCRN can handle a larger number of nodes than a normal GMPLS network. It can also bear more frequent network topology changes than a normal GMPLS network.

Field test of GMPLS all-optical path rerouting

Router-to-router all-optical wavelength path rerouting using generalized multiprotocol label switching protocol has been successfully carried out including photonic cross-connect and dense wavelength-division-multiplexing equipment. The rerouting time was measured to be shorter than 7 s.

Value-added proposition of the GMPLS control plane in IP optical networks

We quantify the value-added proposition of the generalized multiprotocol label switching (GMPLS) distributed control plane vis a vis the centralized network management (CNM) plane. Our main objective is not to propose new protocols or algorithms, but rather to provide guidance to network operators on how to maximize the benefits of deploying a GMPLS control plane. We identify two main goals for maximizing these benefits: (1) decreasing operations costs and (2) increasing revenues through enhancing the efficiency of existing network assets as well as through enabling new services. Control plane functionalities such as dynamic routing, user-initiated end-to-end connection setup, and distributed fault management in IP optical networks are analyzed to determine optimal operating regions where their values are maximized. Extensive simulations using NSFNET topology have been carried out from which we have found that there are certain operating regions where (1) the distributed routing can improve the efficiency of network assets by saving 15% of the number of wavelengths per link, or increasing traffic loads by 20%. However, if the call interarrival time is shorter than 1 min, the efficiency (in terms of call blocking ratio) of distributed dynamic routing is reduced due to the OSPF convergence delay. (2) Enabling bandwidth on demand (BoD) services at finer bandwidth granularities connections is more cost-effective to the operator than doing the same at coarse bandwidth granularities. (3) The connection setup delay is the limiting factor in determining the types of BoD services a carrier offers. The call blocking ratio will increase quickly if the average call interarrival time is less than tens of seconds. (4) Assuming only single link failure, M:N shared protection can achieve 100% recovery at the expense of 10% increase in the number of wavelengths compared with nonprotection schemes, while saving are as high as 48% wavelengths compared with 1:1 dedicated protection.

Traffic engineering featuring dynamic lightpath provisioning in multilayer GMPLS optical networks

Wavelength-routed networks are viewed as less flexible than IP-routed networks because of the dedicated nature of optical path and incurred optical layer constraints, e.g., wavelength continuity constraints. However, current wavelength-routed networks operating in the WDM environment are empowered with the potential of dynamic and fast provisioning of high-bandwidth optical paths. This potential is currently being addressed by intelligent traffic engineering (TE) on multilayer networks that combine both a broadband optical layer and a grooming-capable electronic layer. We propose a dynamic TE scheme within the framework of multilayer generalized multiprotocol label switching (GMPLS), which takes into consideration the simple nature of an all-optical (OOO) path, the flexibility and grooming efficiency of optical-electrical-optical (OEO) connection, and the support of traffic quality of service (QoS). It optimizes the utilization of OOO and OEO connections in a hybrid fashion through the concept of lightpath tunneling that can adapt to real-time traffic demands. Simulations based on this TE scheme show that the optical transceiver requirement it core nodes can be reduced to only ~20% of that of the IP-routed networks without sacrificing performance. This TE scheme can also be adapted to network scenarios where very limited numbers of transceivers are deployed.

Load-balancing contention resolution in OBS networks based on GMPLS

Contention resolution (CR) in optical burst switching (OBS) networks is a hot topic in the academia. However, most previous research was done within the local core switching node. In this paper, we investigate an integrated CR technique in OBS networks based on generalised multi-protocol label switching (GMPLS). At first, a new network model is proposed, in which a label switched path (LSP) is just composed of a series of links and not assigned with any wavelength, and the wavelengths are decided when core switches process the control packets. Then, we propose a novel technique, i.e., load-balancing contention resolution (LBCR), which is divided into two parts: within the network layer, CR is done with load-balancing technology; within the node layer, local CR algorithms can be employed. Simulations show that LBCR can reduce burst contention and burst loss probability.

Low-cost resilience schemes for the Optical Ethernet

"http://www.osa-jon.org/features/OE_2005.html". Feature Issue on Optical Ethernet (OE). Optical Ethernet (OE) architectures transport IP packets directly over the optical layer by providing a specific Layer 2 framing. Although the architectures represent a simple and low-cost solution, the limiting factor for their widespread deployment is represented by the lack of some efficient operation, administration, and maintenance (OA&M) features, such as resilience. Optical layer protection represents a low-cost resilience scheme for OE links. We present the experimental results of low-cost protection implementations that are based on different failure detection and failure protection activation schemes for IP-over-OE networks. Specifically, a dedicated span protection scheme and an evolution for shared protection based on generalized multiprotocol label switching (GMPLS) signaling in transparent domains is presented. Experimental results show that recovery times in the millisecond range are achieved.

Survivable GMPLS networks with QoS guarantees

A scheme is proposed to provide multiple QoS guarantees for survivable generalised multiprotocol label switching (GMPLS) networks. The shared risk link group (SRLG) information is considered to provide failure-independent protection. Based on the problem formulation, the service level agreement (SLA) parameters, such as the expected recovery failure probability, the expected recovery time and the expected signal loss are analysed to reveal the bound of the backup path length. Under the constraint of such a backup path length limit, a heuristic algorithm is further proposed for online path configuration. The simulation results demonstrate that the heuristic algorithm provides recovery quality guaranteed backup paths with high bandwidth multiplexing gain.

Customer-oriented GMPLS service management and resilience differentiation

Generalized Multi-Protocol Label Switching (GMPLS) is currently under standardization at the Internet Engineering Task Force (IETF). It basically reuses the MPLS control plane (IP routing and signaling) for various technologies such as fiber switching, DWDM, SONET, and packet MPLS. In this article, we propose a management architecture, which allows a service provider to offer customers various services based on a GMPLS infrastructure. The business model behind the architecture is comparable to the online flight ticket sales systems known.

Photonic MPLS Internetworking using an Optical Code Label Stack

Generalized multiprotocol label switching (GMPLS), which enables dynamic optical path provisioning, is promising. However, the critical issues of GMPLS in the optical domain are the data granularity of a wavelength and the very exiguous label space. The capacity of a single wavelength path may be sometimes too large to accommodate the traffic between edge node pairs, and the label space may be too small to assign the labels to each packet or flow. To solve the granularity and label space issues, optical code MPLS (OC-MPLS) is proposed. In this paper, OC-MPLS internetworking is introduced and experimentally demonstrated. One of the key techniques is photonic label processing of a label stack attached to a single packet or flow. The proposed method performs routing of packets or flows for interconnected OC-MPLS networks depending on the attached label stack in an all optical manner.

Performance Analysis of a Traffic Engineering Solution for Multilayer Networks Based on the GMPLS Paradigm

This paper presents an integrated traffic engineering (TE) system for new generation multilayer networks based on the generalized multiprotocol label switching (GMPLS) paradigm, and reports the performance analysis of such a system. The proposed TE system aims at dynamically reacting to traffic changes and, at the same time, fulfilling quality of service (QoS) requirements for different classes of service. The proposed solution consists of a hybrid routing approach and a bandwidth management strategy. The former makes use of both off-line and on-line methods to accommodate traffic requests. The latter, based on an "elastic" use of the bandwidth, allows the handling of different priorities among data flows, possible preemptions, and rerouting. The proposed TE permits the accommodation of the largest amount of traffic, while guaranteeing good performance to mission-critical services. The main building blocks and the operations of the system are reported and the major advantages are discussed. The performance of the proposed system are compared with the ones relating to a reasonable alternative system based on overprovisioning, to highlight its advantages of in terms of traffic volume that can be accommodated for a given network infrastructure.

Providing Quality-of-Protection Classes Through Control-Message Scheduling in DWDM Mesh Networks With Capacity Sharing

This paper considers the problem of providing quality-of-protection (QoP) classes and improving the failure-recovery time performance in dense wavelength-division-multiplexing (DWDM) networks that use mesh-based path restoration schemes with capacity sharing. We focus on the signaling process required for reconfiguring the nodes along the preplanned restoration paths, and propose a novel approach for reducing the restoration time and meeting the QoP requirements by coordinating the setup procedures for the backup paths through scheduling. We present priority-based online scheduling algorithms that are amenable to distributed implementation for the problems of: 1) minimizing the worst case restoration time and 2) maximizing the number of connections that meet their QoP-class-specific restoration time deadlines. We also present mixed-integer-linear-program (MILP) formulations for both problems for comparison purposes. The online scheduling methods that we propose use simple connection and/or class-specific information and can be easily implemented with minor modifications to the currently proposed signaling protocols. We apply these methods to signaling protocols that require cross-connect configurations at different nodes to be done in sequence as in the current generalized multiprotocol label switching specification, as well as signaling protocols that allow cross-connect configurations to be done in parallel. It is shown that in both cases, significant performance improvements are achievable through scheduling in terms of both the QoP grades that can be supported and the restoration times, with both the MILP solutions and the heuristics. The improvement in restoration time and restorability through our heuristics can be quite high (e.g., increase from a network restorability performance of 40% to a network restorability of 88%, and a 12% reduction in worst case restoration time).

Design of Optical Full Encoders/Decoders for Code-Based Photonic Routers

This paper demonstrates that standard multiplexers as generalized Mach-Zehnder interferometers or waveguide grating routers can be designed to generate/process a set of orthogonal optical codes (OCs) with very high-correlation performances. The same device can be used at the ingress node of a generalized multiprotocol label switching network to generate the photonic labels and at each routing node to perform all the correlations simultaneously. To enhance the code cardinality, without increasing the code length, this paper shows that it is possible to use the proposed encoder/decoder architectures to generate/process multidimensional OCs.

Resilience in GMPLS path management: model and mechanism

The recent advent of converging the IP and optical networks has necessitated the development of a generalized multiprotocol label switching framework. Resilience becomes more important than ever before in a GMPLS network since a single cut of an optical fiber may generate hundreds of link and node failures at high layers of the GMPLS architecture. In this article we briefly survey the current work regarding GMPLS recovery management, and present a new resilience-based dynamic GMPLS path management strategy. We present a simple model to represent the resilience requirements in GMPLS path management, and propose fast path management algorithms. The salient feature of the proposed approach is that it enables the paths to be dynamically selected under multiple simultaneous failure occurrences while satisfying the resilience requirement. Backup path design rules are developed, and the condition for backup path availability is derived for the special mesh-type GMPLS network. Finally, a simple example is shown to illustrate the effectiveness of the proposed resilience model and path management mechanism.

The Modeling Process and Analysis of Virtual GMPLS Optical Switching Routers

Generalized multi-protocol label switching (GMPLS) has emerged as a very promising protocol technology for the next generation optical networks. GMPLS successfully combines the best features of IP and ATM in terms of quality of service (QoS), privacy, flexibility and scalability. GMPLS introduces enhancements to the existing IP routing and signaling protocols by supporting not only networks that perform packet switching (IP), but also networks that perform switching in the time (TDM), wavelength (DWDM), and space domain (circuit switching). This paper discusses the design and implementation of a modeling tool for analysis of GMPLS optical switching routers (GOSR). A model of the GOSR has been built using OPNETTM modeling and simulation platform, in lieu of a prototype. The virtual model contains all the necessary GMPLS functions of an optical backbone router. The description on the design features and the key implementation elements of the internal mechanism of GOSR forms the introduction of this paper. The virtual model of the GOSR has the capability of giving a more integrated and realistic simulation on wavelength routing, wavelength assignment, wavelength switching, dynamic label switching path (LSP) setup and tear down, and blocking mechanism of GMPLS light paths. The OPNET process modeling methodology was used to develop the virtual GOSR models. The simulation results obtained include the blocking rate, OSPF-TE bandwidth analysis, and CPU utilization. The modeling environment developed in this project provides a simulation platform for further development and future enhancement of GMPLS protocols, routing protocols, and optical switching router implementations.

NEW SCHEMES FOR CONNECTION ESTABLISHMENT IN GMPLS ENVIRONMENT FOR WDM NETWORKS

Generalized Multi-Protocol Label Switching (GMPLS) is growing in popularity as a set of protocols for provisioning and managing core optical networks. In this paper, we present new schemes for provisioning lightpaths in WDM optical network. We first propose a path selection scheme required for deploying lightpaths in GMPLS environment. When a request for lightpath arrives at a source LSR, in GMPLS it is required to send request messages from an upstream LSR to the downstream LSR for setting up a lightpath. Therefore it is needed that an appropriate route be selected through the optical network for the requested lightpath. Keeping in mind its signaling characteristics we describe a path selection algorithm that can be built on GMPLS to enhance its performance. We next propose a path setup scheme for setting up the connection using the path selected with our earlier scheme. The lookahead approach of our path set up scheme enables it to work faster than existing GMPLS path setup protocols. We performed extensive simulation and found that the blocking probability of the WDM networks in GMPLS environment is lower when using our schemes than with the existing standard protocols.