Jose-Luis Izquierdo-Zaragoza

Net2plan: an open source network planning tool for bridging the gap between academia and industry

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 describe 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 userdefined or built-in network design algorithms, network recovery schemes, connection-admission-control systems, or dynamic provisioning algorithms for timevarying traffic. The Net2Plan philosophy enforces code reutilization as an open repository of network planning resources. In this article, 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 article are publicly available on the Net2Plan website.

Educational and research tools for network optimization

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.

Lightpath bundling and anycast switching: a new paradigm for multilayer optical networks

In IP over WDM multilayer optical networks, IP routers are interconnected by all-optical channels called lightpaths, of typical rates of 10, 40, or, more recently, 100 Gb/s. In this context, lightpath bundling (LB) and anycast switching (AS) are control plane and data plane techniques, respectively, both of them to be implemented in the IP routers. LB permits grouping a set of lightpaths between two nodes that follow a common route so that they are perceived by the IP layer as a single virtual link of aggregated capacity. In its turn, AS consists of instructing the router to implement a per-packet-granularity balancing of the traffic among the lightpaths in the bundle, reducing the packet delay and the buffering requirements in the node. This happens transparently to the IP layer, which, because of the LB configuration, sees the bundled lightpaths as a single entity. In this article, we propose the combined application of the LB and AS techniques as a new paradigm (LB+AS) for optical networks. Applying the LB+AS concept requires seamless changes in the electronic equipment and no changes in the optical infrastructure. We present a case study that shows the significant performance and cost benefits LB+AS can bring to the network and its inherent scalability. In addition, we discuss other potential advantages of LB+AS and related open research lines.

Segmentation of the carotid artery in ultrasound images using frequency-designed B-spline active contour

Atherosclerosis is a cardiovascular disease very widespread into population. It is characterized by a thickening of the arterial walls, which affects blood flow. The intima-media thickness (IMT) has emerged as a reliable early indicator of this pathology.

Net2Plan: An integrated open-source framework for multilayer network planning and in-operation simulation

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.

Maximizing IP fast rerouting coverage in survivable IP-over-WDM networks

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.

Guaranteeing Traffic Survivability and Latency Awareness in Multilayer Network Design

The massive adoption of real-time Internet services (e.g., online gaming or video streaming) is threatening the way in which operators and service providers design and operate their networks. New requirements, such as maximum latency, are becoming de facto indicators to measure network quality, complementing the classical requisites of fault tolerance to increase network availability. However, finding fault-tolerant designs that also limit the end-to-end latency of IP flows is challenging in multilayer IP-over-WDM networks, since traffic routed over IP links depends on the actual sequences of the traversed fibers and how they change in each failure state. Despite its practical importance, the research on joint optimization of end-to-end latencies and fault tolerance in multilayer optical networks is minimal. In this context, this paper presents a planning algorithm for multilayer IP-over- WDM (with OSPF-ECMP routing in the IP layer), considering both survivability and end-to-end latency awareness. Three versions of the algorithm are provided, assuming three different recovery mechanisms in the optical layer: 1 + 1 lightpath protection, unprotected lightpaths, and lightpath restoration. In all cases, as is customary, the optical layer is assumed to react first to the failures, and after that, the IP/OSPF layer adapts to the surviving topology. The aim of our algorithm is to design minimum cost networks that guarantee not only 100% survivability under some representative failure states, but also the maximum end-to-end latency for IP flows in the case of any failures. According to our results, a careful and holistic design may achieve both objectives simultaneously, without, in most cases, noticeable side effects in terms of cost and/or throughput. In its turn, we see that, when end-to-end latencies are not considered, designs tend to produce very high latencies in some flows and failure states.

Evaluating add/drop contention blocking in non-contentionless ROADMs

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.

TCP performance in an optical link applying lightpath bundling and anycast switching techniques

Lightpath bundling (LB) technique consists of grouping a set of lightpaths between two nodes so that they appear to the IP layer as a single pipe of aggregated capacity. Anycast switching (AS) technique makes a per-packet granularity balancing of the traffic among the lightpaths bundled. LB+AS combination requires seamless changes in the switching nodes and no changes in the optical infrastructure. This paper evaluates by means of simulation the improvements in TCP performances when LB+AS paradigm is applied to the network. In our results, LB+AS improved TCP throughput (up to 18%), decreased average drop rates and reduced the average queuing delay in the bottleneck link (up to 15%).

Dynamic operation of an IP/MPLS-over-WDM network using an open-source active stateful BGP-LS-enabled multilayer PCE

Leveraging on reference implementations of PCEP and BGP-LS protocols, we have developed an active stateful multilayer PCE extension for the open-source Net2Plan planning tool to orchestrate multilayer service provisioning and restoration in IP/MPLS-over-WDM networks.