Fernando Agraz

Experimental Demonstration of an Impairment Aware Network Planning and Operation Tool for Transparent/Translucent Optical Networks

Core optical networks using reconfigurable optical switches and tunable lasers appear to be on the road towards widespread deployment and could evolve to all-optical mesh networks in the coming future. Considering the impact of physical layer impairments in the planning and operation of all-optical (and translucent) networks is the main focus of the Dynamic Impairment Constraint Optical Networking (DICONET) project. The impairment aware network planning and operation tool (NPOT) is the main outcome of DICONET project, which is explained in detail in this paper. The key building blocks of the NPOT, consisting of network description repositories, the physical layer performance evaluator, the impairment aware routing and wavelength assignment engines, the component placement modules, failure handling, and the integration of NPOT in the control plane are the main contributions of this study. Besides, the experimental result of DICONET proposal for centralized and distributed control plane integration schemes and the performance of the failure handling in terms of restoration time is presented in this study.

Experimental demonstration of centralized and distributed impairment-aware control plane schemes for dynamic transparent optical networks

We demonstrate and compare distributed and centralized impairment-aware control plane schemes for transparent optical networks with dynamic traffic. Experimental results show that distributed scheme yields one fifth of setup time required by previously reported alternatives.

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 failures 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.

SDN-enabled OPS with QoS guarantee for reconfigurable virtual data center networks

Optical packet switching (OPS) can enhance the performance of data center networks (DCNs)by providing fast and large-capacity switching capability. Benefiting from the software-defined networking (SDN) control plane, which could update the look-up-table (LUT) of the OPS, virtual DCNs can be flexibly created and reconfigured. In this work, we have implemented and assessed an SDN-based control framework for an OPS node, where the OpenFlow protocol has been extended in support of the OPS switching paradigm. Application flows are switched by the OPS at submicrosecond hardware speed, decoupled from the slower (millisecond timescale) SDN control operation. By the DCN infrastructure provider, the virtual networks become directly programmable with the abstraction of the underlying OPS node. Experimental results validate the successful setup of virtual network slices for intra-data center interconnect and quality of service (QoS) guarantee for high-priority application flows. Data plane resources are efficiently shared by exploiting statistical multiplexing. In addition, the capability of exposing per-port OPS traffic statistics information to the SDN controller enables the implementation and experimental validation of load balancing algorithms to improve the QoS performance.

Multi-Tenant Software-Defined Hybrid Optical Switched Data Centre

We introduce a holistic solution for software-defined optical data centres (DC). Hybrid optical circuit/packet switching technologies are employed in the data plane, while a software-defined networking (SDN) controller based on OpenDaylight with significant extensions is adopted for the data centre network (DCN) control and management. Novel functional modules in the SDN controller together with its northbound (NBI) and southbound interfaces (SBI) are designed and developed. The OpenFlow protocol is extended at the SBI to support communication between the extended OpenDaylight SDN controller and the optical DCN devices. Over the NBIs, DC applications and the cloud management system directly interact with the optical DCN. A virtual data centre (VDC) application is designed and developed that dynamically creates and provisions multiple coexisting but isolated VDCs. An optical network-aware virtual machine (VM) placement method is proposed and implemented for a single-step deployment of both network and IT (VM) resources to accommodate the VDC requests. The VDC deployment process is extensively simulated and experimentally demonstrated.

Design and Implementation of a GMPLS-Controlled Grooming-Capable Optical Transport Network

Aiming at better resource utilization, an important requirement of future optical transport networks is the capability to accommodate subwavelength client flows efficiently. This can be put into action thanks to the enhanced traffic engineering (TE) protocols provided within the generalized multiprotocol label switching (GMPLS) standardization. The present paper concentrates on the design and implementation of a GMPLS-controlled grooming-capable transport infrastructure, namely, the automatically switched optical network (ASON)/GMPLS CARISMA test bed. Through the paper, the operation of a GMPLS-controlled multilayer network architecture is introduced, subsequently highlighting implementation issues that come to light. Special attention is devoted to a centralized flow reallocation module deployed in the CARISMA test bed to minimize the overall network cost. In this context, an integer linear programming (ILP) formulation to obtain its optimal cost is derived and low-weighted metaheuristics providing a nearly optimal solution are additionally proposed. All contributions in the paper are supported by illustrative experimental results.

Lightness: A Function-Virtualizable Software Defined Data Center Network With All-Optical Circuit/Packet Switching

Modern high-performance data centers are responsible for delivering a huge variety of cloud applications to the end-users, which are increasingly pushing the limits of the currently deployed computing and network infrastructure. All-optical dynamic data center network (DCN) architectures are strong candidates to overcome those adversities, especially when they are combined with an intelligent software defined control plane. In this paper, we report the first harmonious integration of an optical flexible hardware framework operated by an agile software and virtualization platform. The LIGHTNESS deeply programmable all-optical circuit and packet switched data plane is able to perform unicast/multicast switch-over on-demand, while the powerful software defined networking (SDN) control plane enables the virtualization of computing and network resources creating a virtual data center and virtual network functions (VNF) on top of the data plane. We experimentally demonstrate realistic intra DCN with deterministic latencies for both unicast and multicast, showcasing monitoring, and database migration scenarios each of which is enabled by an associated network function virtualization element. Results demonstrate a fully functional complete unification of an advanced optical data plane with an SDN control plane, promising more efficient management of the next-generation data center compute and network resources.

Demonstration of GMPLS-controlled device power management for next generation green optical networks

We propose GMPLS protocol enhancements enabling dynamic power state management of optoelectronic network devices for setup-time-aware differentiated connection provisioning. Daily energy savings of 56% are demonstrated in a Pan-European-like network compared to always on scenarios.

Analysis of traffic engineering information dissemination strategies in PCE-based multi-domain optical networks

This paper presents and compares different TE information dissemination strategies between Path Computation Elements (PCEs) in multi-domain optical networks. In such network context, recent studies have found that path computation only with local domain visibility yields poor network performance. Accordingly, certain visibility between domains seems necessary. Aiming to fit the confidentiality requirements of the composing domains while improving the final network blocking probability, novel link aggregation techniques have been proposed, which summarize the state of network domains resources efficiently. This aggregated link information is afterwards disseminated to all the remainder domains in the network. To this end, we introduce different update triggering policies to make a good trade-off between routing information scalability and inaccuracy. The performance of all contributions has been supported by illustrative simulation results.

Experimental demonstration of a GMPLS-enabled impairment-aware lightpath restoration scheme

Fast lightpath restoration becomes particularly challenging in all-optical networks. First, the optical transparency complicates failure localization and isolation procedures, as loss of light alarms stemming from a failure propagate downstream from the failure point. Besides, such a transparency implies that optical signals must traverse relatively long distances without electrical regeneration. In view of this, backup path computations must also account for all degradations introduced in the physical end-to-end path, thus ensuring their feasibility. Looking toward the optical core networks of the future, the EU DICONET Project has worked on cross-layer solutions to enhance network control and management with the impairment-awareness needed to govern the underlying optical layer. This includes a network planning and operation tool (NPOT) that implements impairment-aware routing and wavelength assignment algorithms, along with a failure localization mechanism. This paper reports the experimental demonstration of a dynamic impairment-aware restoration scheme that benefits from enhanced NPOT features for fast lightpath restoration. To this end, a prioritized scheduler to provide differentiated resilience support, the implementation of the quality of transmission estimator module on field programmable gate array hardware, and a fast resource pre-reservation protocol are presented in this work. The performance of the proposed impairment-aware lightpath restoration scheme has been evaluated experimentally on a 14-node all-optical network test-bed, showing average restoration times of 1.16 and 1.64 s for high and low priority traffic classes, respectively.