Publications

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Journal Papers

1. P. Pavon-Marino, M.V. Bueno-Delgado and J.L. Izquierdo-Zaragoza, "Evaluating Internal Blocking in Noncontentionless Flex-grid ROADMs [Invited]," IEEE/OSA Journal of Optical Communications and Networking (Special Issue OFC2014), vol. 7, no. 3, pp. A474-A481, March 2015. [URL] [JAR]
   Abstract

   In heterogeneous flex-grid networks, optical connections for different line rates, spectral widths, and modulations can coexist in the same infrastructure. Optical connections are transparently routed by reconfigurable add/drop multiplexers (ROADMs). Flex-grid ROADMs are enabled by state-of-the-art evolution from original wavelength-selective switches (WSSs), designed for fixed-grid applications, to WSSs that operate in flexible grids. Broadcast-and-select (B&S) flex-grid ROADMs are subject to the same internal blocking as their fixed-grid counterparts, and this internal blocking can also be reduced by augmenting the number of add/drop transponder banks. In this paper, we dimension the number of transponder banks C required in flex-grid ROADMs to make the internal blocking negligible. To this end, we present a graph transformation that takes a network topology based on B&S ROADMs and converts it into an equivalent network composed of contentionless ROADMs. Then, any conventional (non-contention-aware) algorithm can be applied to the transformed topology to make lightpath allocations. Our results show that often C = 2, and in some cases C = 1, transponder banks are enough to eliminate internal contention in practice. Interestingly, these results are similar to the ones obtained in the fixed-grid case. This is not an obvious conclusion, since spectrum fragmentation in flex-grid networks may amplify internal blocking. Results have been obtained using the Net2Plan 0.2.3 open-source tool. Algorithms' source code and data are available in the Net2Plan public repository for reuse and validation.

2. P. Pavon-Marino and J.L. Izquierdo-Zaragoza, "Net2Plan: An open-source network planning tool for bridging the gap between academia and industry," IEEE Network Magazine, in press. [PDF] [JAR]
   Abstract

   The plethora of network planning results published in top-ranked journals is a good sign of the success of the network planning research field. Unfortunately, it is often difficult for network carriers and ISPs to reproduce these investigations on their networks. This is partially because of the absence of a software planning tool meeting the requirements of industry and academia, which can make the adaptation and validation of planning algorithms less time consuming. We motivate how a paradigm shift to an open-source view of the network planning field emphasizes the power of distributed peer-review and transparency to create high-quality software at an accelerated pace and lower cost. Then, we present Net2Plan, an open-source Java-based software tool. Built on top of a technology-agnostic network representation, it automates the elaboration of performance evaluation tests for user-defined or built-in network design algorithms, network recovery schemes, connection-admission-control systems, or dynamic provisioning algorithms for time-varying traffic. The Net2Plan philosophy enforces code reutilization as an open repository of network planning resources. In this paper, a case study in a multilayer IP-over-WDM network is presented to illustrate the potential of Net2Plan. We cover standard CAPEX studies, and more advanced aspects such as a resilience analysis of the network under random independent failures and disaster scenarios and an energy efficiency assessment of "green" schemes that switch off parts of the network during low load periods. All the planning algorithms in this paper are publicly available on the Net2Plan website.

Conference Papers

1. P. Pavon-Marino, M. V. Bueno-Delgado, J. Lopez-Fernandez, J. San-Emeterio, J. J. Pedreno-Manresa, F. Burrull, Z. Gaubeca-Canalechevarria, M. Tecles, J. L. Izquierdo-Zaragoza, "Net2Plan-Aire: gained experience in an ad-hoc SDN development for a metro carrier network", in Proceedings of the 17th International Network Strategy and Planning Symposium (Networks 2016), Montreal (Canada), September 2016.
2. M.P. Jimenez-Gomez, M.V. Bueno-Delgado and P. Pavon-Marino, "Net2Plan-UTN: An Educational Tool for Modeling and Planning Urban Transportation Networks", in Proceedings of the 8th annual International Conference on Education and New Learning Technologies (EDULEARN 2016), Barcelona (Spain), July 2016.
3. J.L. Izquierdo-Zaragoza, J.J. Pedreno-Manresa, P. Pavon-Marino, O. Gonzalez-de-Dios and V. Lopez, "Dynamic Operation of an IP/MPLS-over-WDM Network Using an Active Stateful BGP/LS-Enabled Multilayer PCE", in Proceedings of the 18th International Conference on Transparent Optical Networks (ICTON 2016), Trento (Italy), July 2016.
   
4. J.J. Pedreno-Manresa, J.L. Izquierdo-Zaragoza and P. Pavon-Marino, "Joint Fault Tolerant and Latency-Aware Design of Multilayer Optical Networks", in Proceedings of the 20th International Conference on Optical Network Design and Modeling (ONDM 2016), Cartagena (Spain), May 2016. Abstract

   When designing a multilayer IP-over-WDM optical network, one important requirement is finding the most cost-effective design that is tolerant to a set of selected failures arbitrarily defined, so the 100% of the IP traffic survives for them. A second concern is the need to guarantee a maximum end-to-end latency for IP traffic (e.g. 50 ms in continental US). Both failure tolerance and latency at the IP layer are quite challenging performance merits to enforce in multilayer networks, since depend on both the IP routing over the lightpaths and the lightpath routing over the fibers, and how they change during recovery processes. There is little research considering one of these concerns separately, and to the best of authors’ knowledge, and just preliminary works on how to design the network jointly considering both requirements. Note that a joint optimization is needed, since e.g. backup routings that do not guarantee end-to-end latency may be useless. In this paper, we address this problem, and present a multilayer planning algorithm to dimension IP/OSPF-over-WDM networks with three main resilience schemes: IP-only restoration, 1+1 lightpath protection followed by IP restoration, and multilayer restoration. Results are provided to validate the algorithms, and feed a discussion on the joint fault and latency-aware multilayer network design under those schemes.

5. J.L. Izquierdo-Zaragoza, J.J. Pedreno-Manresa and P. Pavon-Marino, "Maximizing IP Fast Rerouting Coverage in Survivable IP-over-WDM Networks," in Proceedings of the 41st European Conference on Optical Communication (ECOC 2015), Valencia (Spain), September-October 2015. [JAR]
   Abstract

   We show that IP-over-WDM multilayer networks can be designed to guarantee that a large majority of the traffic is restored at a subsecond timescale, using IP Fast Rerouting techniques. The rationale is enforcing OSPF/ECMP traffic balancing on SRG-disjoint lightpaths.

6. J.L. Izquierdo-Zaragoza, J.J. Pedreno-Manresa and P. Pavon-Marino, "Net2Plan: An Integrated Open-Source Framework for Multilayer Network Planning and In-Operation Simulation," in Proceedings of the 17th International Conference on Transparent Optical Networks (ICTON 2015), Budapest (Hungary), July 2015.
   Abstract

   Multilayer networking is an enabling technology to support the exponential growth of traffic and its dynamicity, with sustainable costs. However, automation and collaboration between layers are still on an early stage. One of the reasons is the absence of pure multilayer planning and management solutions considering the network as a whole entity, where layers cooperate with each other, instead of the sum of individual layers providing isolated services. In this paper, we revisit our open-source Net2Plan tool to present its new multilayer features. The novel technology-agnostic multilayer network model integrates into the Net2Plan offline network design and online network simulation tools, to provide practitioners a framework to understand the benefits of multilayer capabilities.

7. J.L. Izquierdo-Zaragoza and P. Pavon-Marino, "Net2Plan: An Open-Source Multilayer Network Planning Tool and In-Operation Simulator (Demo Paper)," in Proceedings of the IEEE 16th International Conference on High Performance Switching and Routing (HPSR2015), Budapest (Hungary), July 2015.
   Abstract

   In this paper we describe the main features of the open-source Net2Plan tool. Built on top of a technology-agnostic vendor-neutral multilayer network representation, Net2Plan is designed to assist users in the evaluation of built-in or original user-developed planning algorithms. In addition, users can analyze their designs using either reports or a simulation tool for in-operation scenarios like network resilience, connection-admission-control, time-varying traffic resource allocation, or even combinations of them, using built-in or custom event generators or reaction algorithms. We motivate how a paradigm shift to an open-source view of network planning emphasizes the power of distributed peer-review, collaboration cycles and transparency to create high-quality software at an accelerated pace and lower cost.

8. J.L. Izquierdo-Zaragoza and P. Pavon-Marino, "Multilayer Network Planning and Operation Using Open-Source Tools (Tutorial)," in Proceedings of the IEEE 16th International Conference on High Performance Switching and Routing (HPSR2015), Budapest (Hungary), July 2015.
   Abstract

   Continuous advances in network technologies challenge network architects in their attempt to foresee what new technologies deserve resources and investments, what existing infrastructure to keep, and their interplay during migration processes. Moreover, topics like energy efficiency, disaster resilience, or SDN/NFV are being intensively considered and investigated during the last years. As a result, R&D efforts have led to a number of solutions. Unfortunately, it is often difficult for operators to reproduce such results on their networks, maybe due to divergent philosophies between commercial planning tools used in the industry and academic tools. A paradigm shift to an open-source view of network planning could emphasize the power of peer-review and transparency to promote innovation at an accelerated pace and lower cost.
   This tutorial would focus on Net2Plan (http://www.net2plan.com), an open-source tool developed by the authors, and actively used in several courses (>200 students) and research projects since 2012. Built on top of a technology-agnostic multilayer network representation, Net2Plan is designed to assist users in the evaluation of built-in or original user-developed planning algorithms. In addition, users can analyze their designs using either reports or a simulation tool for in-operation scenarios like network resilience, connection-admission-control, time-varying traffic resource allocation, or even combinations of them. Besides, Net2Plan permits applying algorithms to orchestrate OpenFlow-enabled networks interacting with the northbound interface of OpenDaylight.
   Throughout the tutorial, attendees would have the opportunity to learn about the main features of Net2Plan, also discovering some of its applications. At the end of this tutorial, attendees would be guided through an intensive hands-on case study based on an IP-over-WDM network, e.g., including network dimensioning using built-in or user-developed algorithms, WDM line engineering (e.g., EDFA placement, impairment computations), automatic availability calculation under different failure patterns, and automatic simulation of the effects of time-varying traffic and assessment of energy-efficient switch-off techniques.

9. J.L. Izquierdo-Zaragoza, M. Furdek, A. Nag, P. Monti, L. Wosinska and P. Pavon-Marino, "On the Dimensioning of Survivable Optical Metro/Core Networks with Dual-Homed Access," in Proceedings of the IEEE 16th International Conference on High Performance Switching and Routing (HPSR2015), Budapest (Hungary), July 2015. [JAR] (due to confidentiality agreements for DISCUS project partners, topology information is not distributed)
   Abstract

   Long-reach passive optical networks (LR-PONs) are able to effectively support the growing demand of traffic originating from residential and business customers. Failures of metro/core (M/C) nodes serving the traffic to/from the access networks covered by LR-PONs, may potentially affect hundreds or thousands of customers. One way of guaranteeing 100% survivability from single-node failures is to apply dual-homing, where each LR-PON is connected to two M/C nodes, and combine it with node-disjoint dedicated-path protection (DPP). In this paper, we present a new approach to provide network survivability against single M/C node failures. Instead of applying dedicated path protection (DPP) strategy, which can require huge amount of extra resources, we combine an unprotected network design with a dynamic multilayer restoration algorithm. Our aim is to determine a suitable amount of resource overbuild (in terms of extra transponders) needed to provide average connection availability close to that guaranteed by DPP. Preliminary results show that dimensioning for the worst-case scenario among a set of predefined M/C node failures, i.e., the one disrupting the highest number of connections, yields to a cost-effective strategy requiring up to 35% less transponders than DPP, while offering the same average connection availability.

10. J.L. Izquierdo-Zaragoza and P. Pavon-Marino, "Assessing IP vs optical restoration using the open-source Net2Plan tool," in Proceedings of the 16th International Telecommunications Network Strategy and Planning Symposium (NETWORKS 2014), Madeira (Portugal), September 2014. [URL] [JAR]
    Abstract

    Economic sustainability of the ever-increasing traffic requirements is built on the cost reduction of IP-over-WDM backbone networks. These networks are composed of a set of IP routers connected via all-optical circuits (or lightpaths), bypassing intermediate nodes, thanks to reconfigurable optical equipment. Today, traffic survivability is ensured by over-dimensioning the IP layer and using some IP/MPLS fast convergence/reroute mechanism, without making use of the reconfigurability of the optical layer. In this paper, we provide algorithms to dimension an IP-over-WDM network under two different resilience schemes: IP restoration and optical-followed-by-IP restoration. In both cases, the IP routing is controlled by an OSPF-like algorithm. In the optical-followed-by-IP restoration, OSPF reactions to failures are delayed by appropriately setting the OSPF hold-off timer, giving time to lightpath restoration attempts to be completed. We evaluate the performance, in terms of bandwidth requirements and traffic survivability, of these two resilience schemes. Our tests show that optical-followed-by-IP restoration is a cost-efficient alternative to IP restoration, still improving traffic survivability in most cases, without any degree of over-dimensioning. Results were obtained using the open-source Net2Plan tool, and source code is available on the website.

11. J.L. Izquierdo-Zaragoza, M.V. Bueno-Delgado and P. Pavon-Marino, "Evaluating add/drop contention blocking in non-contentionless ROADMs," in Proceedings of the 16th International Conference on Transparent Optical Networks (ICTON 2014), Graz (Austria), July 2014. [URL] [JAR]
    Abstract

    In this paper, we evaluate the capacity reduction in a network composed of directionless-colorless ROADMs, caused by the internal blocking of the ROADMs that are not contentionless. We are interested in determining the number of add/drop modules, so-called add/drop contention factor C, that eliminate this capacity reduction in practice. Under simulation, we show that a moderated contention factor (C=2) is sufficient to roughly provide the same performance as contentionless nodes in terms of either blocking probability in the long-run or carried traffic before the first blocking event. Results were obtained within the Net2Plan tool, and source code is publicly available on Net2Plan website.

12. J.L. Izquierdo-Zaragoza, A. Fernandez-Gambin, J.J. Pedreno-Manresa and P. Pavon-Marino, "Leveraging Net2Plan planning tool for network orchestration in OpenDaylight," in Proceedings of the 5th International Conference on Smart Communications in Network Technologies 2014 (SaCoNeT 2014), Vilanova i la Geltru (Spain), June 2014. [URL]
    Abstract

    The software-defined networking (SDN) paradigm brings unprecedented agility and flexibility to network operators. The usage of centralized software-based controllers simplifies operation and management and enables innovation in the control plane through network programmability. Besides, a controller may be operated via third-party applications using the so-called northbound application programming interfaces (APIs). In this paper, we report our preliminary work on the interaction between the northbound interface of the open-source industry-supported OpenDaylight controller and our Net2Plan tool. Net2Plan is an open-source network planning tool that is able to execute user-made algorithms. By connecting Net2Plan to OpenDaylight, users would be able to easily orchestrate their networks, e.g. defining flow routing, making use of built-in or user-defined algorithms, implemented in the Net2Plan framework. In this paper, we present some illustrative experiments, and discuss future challenges.

13. J.L. Izquierdo-Zaragoza, P. Pavon-Marino and M.V. Bueno-Delgado, "Distance-adaptive online RSA algorithms for heterogeneous flex-grid networks," in Proceedings of the 18th International Conference on Optical Network Design and Modeling (ONDM 2014), Stockholm (Sweden), May 2014. [URL] [JAR]
    Abstract

    Flex-grid elastic optical networks are an enabling technology for future heterogeneous on-demand optical bandwidth services. Heterogeneous means that optical connection requests for different services requiring different data rates, would coexist in the network. In this context, Routing and Spectrum Assignment (RSA) algorithms face the challenge of making a fair allocation of resources, providing a similar blocking performance to all the services.

    In this paper, we review existing RSA proposals applicable to heterogeneous flex-grid networks, evaluating (i) its blocking performance averaged among services, and (ii) the fairness in the blocking observed by each individual service. In addition, we propose the Partial-Sharing-Partitioning (PSP), a scheme to balance both aforementioned metrics. We concentrate on a distance-adaptive scenario, where the same connection request can be carried with different modulations, associated to different spectral efficiencies and optical reaches. Our simulation results in the Net2Plan tool explore the interplay between average blocking and fairness. We observe that many classical RSA algorithms produce unfair allocations, while PSP permits tuning the balance between both metrics. The algorithms developed are publicly available in the open-source Net2Plan repository.

14. P. Pavon-Marino and J.L. Izquierdo-Zaragoza, "On the Role of Open-Source Optical Network Planning", in Proceedings of the 2014 Optical Fiber Communication Conference (OFC 2014), San Francisco (US), March 2014. [URL]
    Abstract

    We argue that open source network planning tools like Net2Plan, and related open repositories of planning resources, can help to bridge the gap between academia and industry speeding-up technology transfer of network planning investigations.

15. J.L. Izquierdo-Zaragoza and P. Pavon-Marino, "Educational and research tools for network optimization", in Proceedings of the 15th International Conference on Transparent Optical Networks (ICTON 2013), Cartagena (Spain), June 2013. [URL]
    Abstract

    This paper presents Net2Plan tool and Java Optimization Modeler (JOM) library and discusses their application as research tools and educational resources in the field of network optimization. Net2Plan is designed to assist users in the definition and comparative evaluation of their original network planning algorithms, as well as in the simulation and testing of connection admission control algorithms, and network protection/restoration schemes. In its turn, JOM is a library which helps to model optimization problems in the Java language and solve them interfacing with integrated linear and non-linear solvers. JOM promotes a fast problem prototyping following a vectorial MATLAB-like syntax. The combined use of Net2Plan and JOM gives users from industry and academia a complete environment to simulate, analyze, dimension, optimize and evaluate the performance of their network designs. Both tools can be publicly downloaded from their respective websites.

Media

1. J. W. Rupe, "Net2Plan is worth a look," Science of Nines [URL]