Multiprotocol Label Switching Control Plane Research Articles

Maximally node and SRLG-disjoint path pair of min-sum cost in GMPLS networks: a lexicographic approach

Path protection is a fast and capacity-efficient approach for increasing the availability of end-to-end connections. However, sometimes it is not possible to obtain a fully disjoint path pair. In this case, it may be admissible to consider a path pair which is as disjoint as possible, and thus provide the best (in a certain sense) level of the single-fault protection that can be ensured using this type of approach. A shared risk link group (SRLG) is a group of links which have a common risk of failure. Two new heuristics for solving the min-sum maximally node and SRLG-disjoint path pair are presented. The relative performance of the new heuristics and also of two other previously proposed heuristics is evaluated using four different networks. Results, regarding accuracy and execution time of the studied heuristics, show that one of the new proposed algorithms can be a good compromise for use in the Generalized Multi-protocol Label Switching control plane.

Strategies for optical transport network recovery under epidemic network failures

The current trend in deploying automatic control plane solutions for increased flexibility in the optical transport layer leads to numerous advantages for both the operators and the customers, but also pose challenges related to the stability of the network and its ability to operate in a robust manner under different failure scenarios. This work evaluates two rerouting strategies and proposes four policies for failure handling in a connection-oriented optical transport network, under generalized multiprotocol label switching control plane. The performance of the strategies and the policies are evaluated under multiple correlated large-scale failures. We employ the Susceptible---Infected---Disabled epidemic failure spreading model and look into possible trade-offs between resiliency and resource efficiency. Via extensive simulations, we show that source rerouting outperforms on-site rerouting, and that there exist a clear trade-off between policy performance and network resource consumption, which must be addressed by network operators for improved robustness of their transport infrastructures. Applying proactive methods for avoiding areas where epidemic failures spread results in 50 % less connections requiring recovery, which translates in improved quality of service to customers and lower recovery expenses for the network operator.

Overarching Control of Flexi Grid Optical Networks: Interworking of GMPLS and OpenFlow Domains

Optical transport networks provide transport, multiplexing, routing, management, supervision, and survivability of optical channels. Within a flexible dense wavelength division multiplexing grid, the optical spectrum can be allocated in multiples of a width granularity, depending on the client signal rate and modulation format. A control plane (CP) can be used for efficient and dynamic provisioning and recovery of flexi-grid connections. Two main CP architectures coexist, with common functions like addressing, automatic topology discovery, network abstraction, path computation, and connection provisioning: a distributed generalized multiprotocol label switching CP (with optional path computation element, PCE path computation and instantiation/modification) and a CP based on software-defined networking, with a logically centralized controller and an open protocol, such as the OpenFlow protocol. Both architectures have their own strengths and weaknesses, and are being extended to address the new requirements associated with the aforementioned emerging optical technologies, such as flexible spectrum allocation, efficient corouted connection setup, and configuration of related optical parameters. However, new use cases such as remote data center interconnection highlight the need for multidomain service provisioning, and heterogeneous CP interworking, potentially requiring an overarching control. Different alternatives, with varying degrees of integration and flexibility, are available: straightforward approaches characterized by the adaptation of one control model to the other or more advanced interworking requiring the definition of common models (e.g., a subset of attributes for network elements) and of coordination and orchestration functions. This paper discusses the main relevant interworking architectures and presents a selected set of use cases and proof-of-concepts.

Resolving epidemic network failures through differentiated repair times

In this study, the authors investigate epidemic failure spreading in large-scale transport networks under generalised multi-protocol label switching control plane. By evaluating the effect of the epidemic failure spreading on the network, they design several strategies for cost-effective network performance improvement via differentiated repair times. First, they identify the most vulnerable and the most strategic nodes in the network. Then, via extensive event-driven simulations they show that strategic placement of resources for improved failure recovery has better performance than randomly assigning lower repair times among the network nodes. They believe that the event-driven simulation model can be highly beneficial for network providers, since it could be used during the network planning process for facilitating cost-effective network survivability design.

Virtual Optical Network Resource Allocation Using PCE Global Concurrent Optimization for Dynamic Deployment of Virtual GMPLS-Controlled WSON

We present dynamic virtual optical network resource allocation (VON RA) algorithms for on-demand deployment of virtual wavelength switched optical networks (WSONs), which is handled by a resource broker with a virtual network topology manager (VNTM). The resource broker with VNTM dynamically configures and deploys independent instances of virtual WSONs over the same physical optical infrastructure and their own independent virtual generalized multiprotocol label switching control plane. The VON RA is computed by a path computation element using global concurrent optimization, which assigns the resources for the virtual optical links (e.g., wavelengths) and nodes. The experimental assessment and performance evaluation have been carried out in the ADRENALINE testbed. We discuss the obtained results on a National Science Foundation Network topology in terms of the VON request blocking rate and VON setup delay, which are used to compare the different proposed algorithms.

Collision-Aware Routing and Spectrum Assignment in GMPLS-Enabled Flexible-Bandwidth Optical Network

In a flexible-bandwidth optical network (FBON) with a generalized multiprotocol label switching control plane, the resource reservation protocol with traffic engineering extensions (RSVP-TE) is employed to establish end-to-end bandwidth variable lightpaths. The resource reservation can be blocked due to spectrum contention of different concurrent RSVP instances (called backward blocking), and it is the predominant blocking contribution when traffic load is low and arrival highly dynamic. Also, due to its flexible traffic granularity in FBON, the backward collision would happen more frequently and the collision scenario would be more complicated than that in wavelength-routed networking; thus the need for a collision evaluation and avoiding method. So, a collision-avoiding routing with maximum available spectrum allocation (SA) options and an SA scheme to search the spectrum segment with minimum collision possibility are proposed for backward blocking reduction, as well as an extension to the RSVP-TE. Simulation results show that the proposed algorithm could achieve better blocking performance through significantly reducing the backward reservation collision but with acceptable forward blocking deterioration. At the same time, with the proposed algorithm, different granularity traffic could be served more fairly in FBON.

Photonic Provisioning Using a Packaged SOI Hybrid All-Optical Wavelength Converter in a Meshed Optical Network Testbed

We demonstrate path wavelength routing and switching using a packaged and pigtailed hybrid integrated silicon-on-insulator (SOI) photonic circuit. The fabricated device incorporates a 1.25 mm nonlinear semiconductor optical amplifier mounted on the SOI board and two multimode interference-based cascaded delay interferometers monolithically integrated on the same SOI substrate. The photonic chip has a footprint of 384 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and performs all-optical wavelength conversion at ultrafast data rates. The packaged and pigtailed module is inserted and tested as a switching node in a meshed optical network testbed carrying real data traffic and encompassing a wavelength division multiplexing optical link. Optical path wavelength switching and routing is implemented by a generalized multiprotocol label switching control plane. We present 10 GbE video-streaming routing as well as 40 Gb/s wavelength switching employing the system integrated all-optical wavelength converter. Error-free transmission and different kind of end-to-end services (video distribution, audio conference, and video conference) have been successfully evaluated.

A Dynamic Path-Computation Algorithm for a GMPLS-Enabled Multi-layer Network

In this paper, we propose a path-computation algorithm for a dynamic virtual network topology (VNT) configuration. We focus on a multi-layer network formed by a connection-oriented Ethernet over a wavelength-switched optical network under the framework of a unified generalized multi-protocol label-switching control plane. The algorithm chooses the route depending on the current state of the network resources, favoring the usage of virtual and forwarding adjacency (FA) traffic engineering (TE) links over a new lambda switching capability (LSC) label-switched path (LSP) establishment. The performance evaluation of the proposed algorithm is conducted through simulations according to three different operational scenarios for the VNT configuration: dynamic, in which all LSC LSPs are established and released dynamically, semi-dynamic, in which a set of FA LSC LSPs is pre-established and advertised by a routing protocol as FA TE links, and virtual, in which a set of FA TE links is pre-defined, but not established. Two different topologies are used: NSFNET and Pan-European. It is shown that the proposed algorithm significantly reduces the connection-blocking probability compared to the algorithms found in the literature, providing an efficient collaboration between the switching layers involved.

Elastic and adaptive optical networks: possible adoption scenarios and future standardization aspects

There is growing recognition that we are rapidly approaching the physical capacity limit of standard optical fiber. It is important to make better use of optical network resources to accommodate the ever-increasing traffic demand. One promising way is to introduce elasticity and adaptation into the optical domain through more flexible spectrum allocation, where the required minimum spectral resources are allocated adaptively based on traffic demand and network conditions. In this article, we discuss elastic and adaptive optical networks from the perspective of future standardization. We first overview the architecture, enabling technologies, and benefits of elastic and adaptive optical networks with the new concept of an optical corridor. We then present possible adoption scenarios from current rigid optical networks to elastic and adaptive optical networks. We discuss some possible study items that are relevant to the future standardization activities. These items include optical transport network architecture, structure and mapping of the optical transport unit, automatically switched optical network/generalized multiprotocol label switching control plane issues, and some physical aspects with possible extension of the current frequency grid.

Sleeping Link Selection for Energy-Efficient GMPLS Networks

To improve the energy efficiency of optical networks, strategies and technologies should aim at ensuring a (low) power consumption proportional to the network utilization. To achieve such aim, this paper proposes the support of sleep mode in the links of a wavelength-switched optical network with generalized multiprotocol label switching control plane. A centralized strategy (to be performed at the Path Computation Element-PCE) and a distributed strategy are proposed to dynamically select the link to be set to sleep. Performance of the proposed strategies is evaluated for different parameter settings. Results show a significant reduction of the overall power drained by the optical devices with both strategies and a contained impact on lightpath blocking probability. The tradeoff between blocking and energy saving of the two strategies is discussed to derive the most energy-efficient and energy-proportional strategy, with negligible impact on the quality of service.

GMPLS-Based Multiple Failure Recovery Employing Restoration Scheme Escalation in Optical Path Networks

Bolstering survivable backbone networks against multiple failures is becoming a common concern among telecom companies that need to continue services even when disasters occur. This paper presents a multiple-failure recovery scheme that considers the operation and management of optical paths. The presented scheme employs scheme escalation from pre-planned restoration to full rerouting. First, the survivability of this scheme against multiple failures is evaluated considering operational constraints such as route selection, resource allocation, and the recovery order of failed paths. The evaluation results show that scheme escalation provides a high level of survivability even under operational constraints, and this paper quantitatively clarifies the impact of these various operational constraints. In addition, the fundamental functions of the scheme escalation are implemented in the Generalized Multi-Protocol Label Switching control plane and verified in an optical-cross-connect-based network.

Multi-ASON and GMPLS network domain interworking challenges

This article describes the intercarrier external network-to-network interface development challenges at the Kei-han-na Info-Communications Open Laboratory. The E-NNI prototype that was developed provides interworking functionality between the automatically switched optical network control plane function of the ITU-T and the generalized multiprotocol label-switching control plane function of the IETF. In this article, an analysis of the differences between ASON network technologies and GMPLS network technologies, a detailed signaling protocol and routing protocol interworking mechanism, and the interworking experimental results of nationwide ASON and GMPLS network domains are described.

Enhanced Security Strategies for MPLS Signaling

In an increasingly hostile environment, the need for security in network infrastructure is stronger than ever, especially for Multi-Protocol Label Switching (MPLS), widely used to provide most of the new-generation network infrastructure-level services in the Internet. Unfortunately, the MPLS control plane lacks scalable verification for the authenticity and legitimacy of signaling messages and communication between peer routers is subject to active and passive forgery, hijacking and wiretapping activities. In this paper, we propose a robust framework for MPLS-based network survivability against security threats. The security of MPLS control plane protocols can be greatly enhanced by requiring digital signature of all the signaling messages, in accordance with a common security paradigm valid for all the protocols. Our design goals include integrity safeguarding, protection against replay attacks, and gradual deployment, with routers not supporting authentication breaking the trust chain but operating undisturbed under any other respect.