OSHI - Open Source Hybrid IP/SDN networking (and its emulation on Mininet and on distributed SDN testbeds)

The introduction of SDN in IP backbones requires the coexistence of regular IP forwarding and SDN based forwarding. The former is typically applied to best effort Internet traffic, the latter can be used for different types of advanced services (VPNs, Virtual Leased Lines, Traffic Engineering...). In this paper we first introduce the architecture and the services of an "hybrid" IP/SDN networking scenario. Then we describe the design and implementation of an Open Source Hybrid IP/SDN (OSHI) node. It combines Quagga for OSPF routing and Open vSwitch for OpenFlow based switching on Linux. The availability of tools for experimental validation and performance evaluation of SDN solutions is fundamental for the evolution of SDN. We provide a set of open source tools that allow to facilitate the design of hybrid IP/SDN experimental networks, their deployment on Mininet or on distributed SDN research testbeds and their test. Finally, using the provided tools, we evaluate key performance aspects of the proposed solutions. The OSHI development and test environment is available in a VirtualBox VM image that can be downloaded.Comment: Final version (Last updated August, 2014

ICONA: a peer-to-peer approach for Software Defined Wide Area Networks using ONOS

Several Internet Service Providers (ISP) are plan- ning to innovate their infrastructures through a process of network softwarisation and programmability. The Software- Defined-Network (SDN) paradigm aims at improving the design, configuration, maintenance and service provisioning agility of the network through a centralised software control plane which is in charge of managing the entire system. This is easily achievable for local area networks, typical of data centres, where the benefits of having programmable access to the entire network is not restricted by latency. However, in Wide Area Networks, a centralised control plane limits the speed of responsiveness in reaction to time-constrained network events due to unavoidable latencies caused by physical distances. A logical step towards robustness in SDN is to distribute the load of the control plane between entities, each taking care of a portion of the entire geographical network and each providing an east-west communication interface to enable programmability of the entire network. Moreover, a key objective of an SDN control plane targeting an ISP networks is the east-west interface with external domains under the control of other providers. In this article we present ICONA (Inter Cluster Onos Network Application), a tool that has the objective of enabling programmable networks to span multiple clusters of controllers within either a single or multiple administrative domains. In particular, the paper describes the architecture behind ICONA and provides an initial evaluation obtained on a preliminary version of the tool, built on top of the cutting-edge network controller ONOS, Hummingbird release

Hybrid IP/SDN networking: open implementation and experiment management tools

The introduction of SDN in large-scale IP provider networks is still an open issue and different solutions have been suggested so far. In this paper we propose a hybrid approach that allows the coexistence of traditional IP routing with SDN based forwarding within the same provider domain. The solution is called OSHI - Open Source Hybrid IP/SDN networking as we have fully implemented it combining and extending Open Source software. We discuss the OSHI system architecture and the design and implementation of advanced services like Pseudo Wires and Virtual Switches. In addition, we describe a set of Open Source management tools for the emulation of the proposed solution using either the Mininet emulator or distributed physical testbeds. We refer to this suite of tools as Mantoo (Management tools). Mantoo includes an extensible web-based graphical topology designer, which provides different layered network "views" (e.g. from physical links to service relationships among nodes). The suite can validate an input topology, automatically deploy it over a Mininet emulator or a distributed SDN testbed and allows access to emulated nodes by opening consoles in the web GUI. Mantoo provides also tools to evaluate the performance of the deployed nodes.Comment: Accepted for publication in IEEE Transaction of Network and Service Management - December 2015 http://dx.doi.org/10.1109/TNSM.2015.250762

Starbursts in isolated galaxies. I. The influence of stellar birth function and IMF

Starbursts and substantial variations in the star formation histories are a common phenomenon in galaxies. We study the stability properties of isolated star-forming dwarf galaxies with the aim of identifying starburst modes. The impact of the stellar birth function, the initial mass function (IMF), the stellar feedback and the interstellar medium (ISM) model are investigated. We apply a one-zone model for a star-gas system coupled by mass and energy transfer. Additionally, we extend the network for active dynamical evolution. This allows for a coupling between the dynamical state of the galaxy and its internal properties. While the influence of the dynamics on the total star formation rate is strong, the coupling of the internal properties (gas temperature) on the dynamics is rather limited, because radiative cooling keeps the gas temperature well below the virial temperature. Because of short cooling and feedback timescales, the star formation rate is close to the equilibrium star formation rates. Quasi-periodic starbursts occur, because star formation follows the variations in the gas density induced by decaying virial oscillations. This behaviour is quite insensitive to the nature and the details of the stellar birth description, viz. whether spontaneous or induced star formation is considered or the IMF is varied. A second type of burst is found as an instability operating when the cooling may drop at very low densities with increasing temperature. Bursts of star formation occur during transitory phases, when dynamical equilibrium is established. Then they are quasi-periodic on the dynamical timescale. Because of short heating and cooling timescales, the star formation rate follows the equilibrium star formation rate corresponding to the actual gas density.Comment: 16 pages, 16 figures, accepted for publication in Astronomy & Astrophysic

Double vs single internal thoracic artery harvesting in diabetic patients: role in perioperative infection rate

Background: The aim of this prospective study is to evaluate the role in the onset of surgical site infections of bilateral internal thoracic arteries harvesting in patients with decompensated preoperative glycemia. Methods: 81 consecutive patients with uncontrolled diabetes mellitus underwent elective CABG harvesting single or double internal thoracic arteries. Single left ITA was harvested in 41 patients (Group 1, 50.6%), BITAs were harvested in 40 (Group 2, 49.4%). The major clinical end points analyzed in this study were infection rate, type of infection, duration of infection, infection relapse rate and total hospital length of stay. Results: Five patients developed sternal SSI in the perioperative period, 2 in group 1 and 3 in group 2 without significant difference. All sternal SSIs were superficial with no sternal dehiscence. The development of infection from the time of surgery took 18.5 ± 2.1 and 7.3 ± 3.0 days for Groups 1 and 2 respectively. The infections were treated with wound irrigation and debridement, and with VAC therapy as well as with antibiotics. The VAC system was removed after a mean of 12.8 ± 5.1 days, when sterilization was achieved. The overall survival estimate at 1 year was 98.7%. Only BMI was a significant predictor of SSI using multivariate stepwise logistic regression analysis (Odds Ratio: 1.34; 95%Conficdence Interval: 1.02–1.83; p value: 0.04). In the model, the use of BITA was not an independent predictor of SSI. Conclusion: CABG with bilateral pedicled ITAs grafting could be performed safely even in diabetics with poor preoperative glycaemic control

Demonstrating a distributed and version-agnostic OpenFlow slicing mechanism

Several virtualization frameworks have been proposed in the last few years for Software Defined Networks (SDN), however, they are either based on proxy-based solutions that raises scalability and robustness issues (FlowVisor), or they leverage on a simplified view of the data-path (generally based on Open vSwitch instances) that have little chances to be adopted in production network settings. In our demonstration we present preliminary results obtained by deploying and using a novel OpenFlow-based network virtualization mechanism. The mechanism is based on a recently proposed distributed virtualization architecture that is able to run on multi-version OpenFlow scenarios

A Distributed Network Monitoring Framework for Wireless Networks

Multi-hop wireless networks are emerging as a viable alternative for building access networks in areas where conventional solutions (cellular, fiber) are neither feasible nor attractive from an economical standpoint. The management of such networks represents an overly complex task because of the time-varying nature of the radio channel, the mobility of users and the presence of adaptive, self-configuration features. Various solutions are currently being researched, whereby network management functionalities are performed autonomously at the network nodes themselves. Such approaches require a monitoring framework able to bring network-level information to the relevant decision points in an effective and robust manner. In this paper, we present a distributed network monitoring framework, specifically developed for wireless multi-hop networks. The system architecture and the protocols are presented together with results obtained using a prototypical implementation over a real-world testbed. Experimental results show that the framework generates a limited amount of traffic, and that the system is able to consistently recover from node failures

A Proposal for End-to-End QoS Provisioning in Software-Defined Networks

This paper describes a framework application for the control plane of a network infrastructure; the objective is to feature end-user applications with the capability of requesting at any time a customised end-to-end Quality-of-Service profile in the context of dynamic Service-Level-Agreements. Our solution targets current and future real-time applications that require tight QoS parameters, such as a guaranteed end-to-end delay bound. These applications include, but are not limited to, health-care, mobility, education, manufacturing, smart grids, gaming and much more. We discuss the issues related to the previous Integrated Service and the reason why the RSVP protocol for guaranteed QoS did not take off. Then we present a new signaling and resource reservation framework based on the cutting-edge network controller ONOS. Moreover, the presented system foresees the need of considering the edges of the network, where terminal applications are connected to, to be piloted by distinct logically centralised controllers. We discuss a possible inter-domain communication mechanism to achieve the end-to-end QoS guarantee