COMPOSER: A compact open-source service platform

Compute and network virtualization enable to deliver network services with unprecedented agility and flexibility based on (a) the programmatic placement of service functions across the available infrastructure and (b) the real-time setup of the corresponding network paths. This paper presents and validates COMPOSER, a compact, flexible and high-performance service platform for the deployment of network services. COMPOSER supports multiple virtualization engines (e.g., virtual machines, containers, native network functions) and it can use seamlessly the above different execution environments to instantiate network services belonging to different chains, hence facilitating domain-oriented orchestration and enabling the joint optimization of compute and network resources. We demonstrate that COMPOSER can run on resource-constrained hardware, such as residential gateways, as well as on high-performance servers. Finally, COMPOSER integrates optimized data plane components that enable our platform to reach top-class results with respect to data plane performance as well

Service Evolution in a Nomadic Wireless Environment

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Autophagy and Schizophrenia: A Closer Look at How Dysregulation of Neuronal Cell Homeostasis Influences the Pathogenesis of Schizophrenia

Autophagy, the process of degrading intracellular components in lysosomes, plays an important role in the central nervous system by contributing to neuronal homeostasis. Autophagic failure has been linked to neurologic dysfunction and a variety of neurodegenerative diseases. Recent investigation has revealed a novel role for autophagy in the context of mental illness, namely in schizophrenia. This article summarizes the phenomenology, genetics, and structural/histopathological brain abnormalities associated with schizophrenia. We review studies that demonstrate for the first time a connection between autophagy malfunction and schizophrenia. Transcriptional profiling in schizophrenia patients uncovered a dysregulation of autophagy-related genes spatially confined to a specific area of the cortex, Brodmann Area 22, which has been previously implicated in the positive symptoms of schizophrenia. We also discuss the role of autophagy activators in schizophrenia and whether they may be useful adjuvants to the traditional antipsychotic medications currently used as the standard of care. In summary, the field has progressed beyond the basic concept that autophagy impairment predisposes to neurodegeneration, to a mechanistic understanding that loss of autophagy can disrupt neuronal cell biology and predispose to mood disorders, psychotic symptoms, and behavioral change.

Does inter-vertebral range of motion increase after spinal manipulation? A prospective cohort study.

Background: Spinal manipulation for nonspecific neck pain is thought to work in part by improving inter-vertebral range of motion (IV-RoM), but it is difficult to measure this or determine whether it is related to clinical outcomes. Objectives: This study undertook to determine whether cervical spine flexion and extension IV-RoM increases after a course of spinal manipulation, to explore relationships between any IV-RoM increases and clinical outcomes and to compare palpation with objective measurement in the detection of hypo-mobile segments. Method: Thirty patients with nonspecific neck pain and 30 healthy controls matched for age and gender received quantitative fluoroscopy (QF) screenings to measure flexion and extension IV-RoM (C1-C6) at baseline and 4-week follow-up between September 2012-13. Patients received up to 12 neck manipulations and completed NRS, NDI and Euroqol 5D-5L at baseline, plus PGIC and satisfaction questionnaires at follow-up. IV-RoM accuracy, repeatability and hypo-mobility cut-offs were determined. Minimal detectable changes (MDC) over 4 weeks were calculated from controls. Patients and control IV-RoMs were compared at baseline as well as changes in patients over 4 weeks. Correlations between outcomes and the number of manipulations received and the agreement (Kappa) between palpated and QF-detected of hypo-mobile segments were calculated. Results: QF had high accuracy (worst RMS error 0.5o) and repeatability (highest SEM 1.1o, lowest ICC 0.90) for IV-RoM measurement. Hypo-mobility cut offs ranged from 0.8o to 3.5o. No outcome was significantly correlated with increased IV-RoM above MDC and there was no significant difference between the number of hypo-mobile segments in patients and controls at baseline or significant increases in IV-RoMs in patients. However, there was a modest and significant correlation between the number of manipulations received and the number of levels and directions whose IV-RoM increased beyond MDC (Rho=0.39, p=0.043). There was also no agreement between palpation and QF in identifying hypo-mobile segments (Kappa 0.04-0.06). Conclusions: This study found no differences in cervical sagittal IV-RoM between patients with non-specific neck pain and matched controls. There was a modest dose-response relationship between the number of manipulations given and number of levels increasing IV-RoM - providing evidence that neck manipulation has a mechanical effect at segmental levels. However, patient-reported outcomes were not related to this

Design and implementation of the OFELIA FP7 facility: The European OpenFlow testbed

The growth of the Internet in terms of number of devices, the number of networks associated to each device and the mobility of devices and users makes the operation and management of the Internet network infrastructure a very complex challenge. In order to address this challenge, innovative solutions and ideas must be tested and evaluated in real network environments and not only based on simulations or laboratory setups. OFELIA is an European FP7 project and its main objective is to address the aforementioned challenge by building and operating a multi-layer, multi-technology and geographically distributed Future Internet testbed facility, where the network itself is precisely controlled and programmed by the experimenter using the emerging OpenFlow technology. This paper reports on the work done during the first half of the project, the lessons learned as well as the key advantages of the OFELIA facility for developing and testing new networking ideas. An overview on the challenges that have been faced on the design and implementation of the testbed facility is described, including the OFELIA Control Framework testbed management software. In addition, early operational experience of the facility since it was opened to the general public, providing five different testbeds or islands, is described

A Study of Connection Management Approaches for an impairment-aware Optical Control Plane

Abstract. Transparent optical networks need novel connection management approaches to take into account the presence of physical impairments in lightpath provisioning. Two main schemes are emerging from literature when considering how to introduce impairment-aware mechanisms in a distributed optical control plane like GMPLS. A well-known approach is based on extending the routing protocol to compute an optically-feasible light-path. Lately, a new approach is emerging which keeps the routing protocol unmodified while leveraging on signaling protocol extensions to find the proper lightpath for the incoming connection request. The aim of this paper is to prove that the signaling-based approach has several advantages compared to the routing-based one, in term of scalability and robustness especially when link information changes are frequent in the network. Simulation results show that a signaling-based approach is much more robust to inaccurate information about network status, therefore it is a suitable approach for considering physical impairments in dynamic optical networks

PrimeNet - Ein optisches Packetnetz auf Basis eines Arrayed Waveguide Gratings

Die vorliegende Arbeit beschreibt eine neuartige Architektur optischer Multihop-Packetnetze und untersucht daraus hervorgehende Zugriffsprotokolle und Fairnessalgorithmen. Die Netzarchitektur basiert auf einem (NxN) AWG, einem passiven Bauelement, das ähnlich einem Prisma in der Lage ist, Wellenlängen zu demultiplexen bzw. zu multiplexen, allerdings mit einer zyklischen Vertauschung der Wellenlängen an den Ausgängen. Durch diese Vertauschung sind keinerlei Kollisionen von Signalen im Bauelement möglich und dieselbe Wellenlänge lässt sich von allen angeschlossenen Stationen gleichzeitig verwenden, was zu einer Vervielfachung der Bandbreite gegenüber einer passiven Sternkoppler-Architektur führt. Auf Basis einer physischen Sternarchitektur werden nunmehr logische Ringe auf jeder Wellenlänge gebildet. Es wird gezeigt, dass die Anzahl der Knoten im Netz eine Primzahl sein muss, damit alle Knoten auf allen (N-1) Ringen liegen. Der Ausbau des Netzes kann mit nur einer Wellenlänge (und nur einem Sender/Empfängerpaar pro Knoten) beginnen, um nach Bedarf weitere Ringe zu installieren. Die Reihenfolge der Knoten in den Ringen ist aber unterschiedlich, was bei einem vollen Ausbau zur Totalvermaschung des Netzes führt. Die Kapazität des Netzes wird analytisch als Funktion der Anzahl der Ringe berechnet. Es wird gezeigt, dass die totale Netzkapazität mehr als quadratisch mit der Zahl der Ringe wächst. Ein Vergleich mit einer Single-Hop-Architektur ergibt, dass im allgemeinen eine sehr geringe Anzahl (2-3) fester Sender/Empfängerpaare ausreicht, um dieselbe Kapazität wie mit einem Paar abstimmbarer Sender/Empfänger pro Knoten zu erreichen. Auf Basis der sich überlagernden Ringe wird dann eine Knotenarchitektur entwickelt, die ein einfaches Zugriffsprotokoll ermöglicht. Ein Vielfachzugriffsverfahren, basierend auf einer optischen Verzögerungsleitung und einer elektronischen Auswertung des Packetheaders, wird daraufhin simulativ untersucht. Um Zeit für die Auswertung des Headers und das optische Schalten zu gewinnen, werden kleinere Packete zu sogenannten "Jumbo"-Rahmen aggregiert. Zur Gewährleistung der Fairness beim Zugriff auf den Ring wird ein lokales Verfahren benutzt, das aus dem SRP-Protokoll hervorging. Dieses Verfahren musste an die optische Knotenarchitektur angepasst werden. Eine simulative Untersuchung zeigt Schwachstellen des Verfahrens auf, wenn statt eines unidirektionalen Datenverkehrs das tatsächliche Verhalten des TCP-Transportprotokolls nachgebildet wird. Die Einführung eines Alarmgebers, der die Wartezeit des ersten Segments in der Warteschlange überwacht, führt zu einem fairen Zugriff aller Knoten auf das Medium. Weitere Probleme treten durch das Umordnen von Aggregaten im Netz auf. TCP reagiert aufgrund des "fast-retransmit"-Mechanismus mit einer schnellen Wiederholung verloren "geglaubter" Packete und einer Reduktion der Senderate. Eine Diskussion der Möglichkeiten, TCP robust gegen solche Fehler zu machen, beschließt das Kapitel. Der letzte Teil der Arbeit bietet einen Ausblick auf Möglichkeiten, größere Netze auf PrimeNet-Basis zu entwerfen. Hierfür bieten sich die sogenannten Cayley-Graphen an, Permutationsgraphen, deren Eigenschaften wie maximale Fehlertoleranz und einfaches Routing von vornherein bekannt sind.This work presents PrimeNet, a novel architecture for optical multihop networks and investigates a Medium Access Control (MAC) protocol and a fairness algorithm for it. The network architecture is based on an Arrayed Waveguide Grating, a passive optical device that is used widely as wavelength multiplexer/demultiplexer, today. Relying on a physical star architecture logical rings are set up on each wavelength. The number of nodes N has to be a prime number to lead to (N-1)/2 pairs of counterdirectional rings. It is possible to start the deployment of the network with a single ring, and to add further rings when the demand increases. With the addition of new rings the mean hop distance in the multihop network decreases from N/2 down to 1, which is the full mesh. The capacity of this multihop network is compared to a single-hop network. It shows that a small number of fixed transmitters and receivers per node (2 to 3, mostly) are enough to gain the same capacity as a single-hop network with one tunable transmitter/receiver pair. On the basis of the proposed multi-ring architecture a node structure, a MAC protocol, and a fairness algorithm are developed and evaluated analytically and by simulation. An estimation of some physical parameters shows that the network is suitable for the local and metropolitan area. The MAC protocol is based on a carrier-sensing and a fiber delay line (FDL) large enough to store a full packet in order to allow for an unslotted, immediate access to the medium. An aggregation of smaller packets to so-called "Jumbo"-frames helps to reduce the overhead for optical switching. Because of the potentially very small mean hop distance, we favor local fairness algorithms over global. Among three candidates, the back-pressure based Spatial Reuse Protocol (SRP) was chosen for the fairness algorithm. It had to be modified to suit the optical node architecture. The simulations of the fairness algorithm were performed using unidirectional traffic with a packet size distribution that is typical for today's Internet. While a fair access to the medium can obviously be guaranteed for this kind of traffic, a modeling of "real" TCP revealed interactions between the MAC protocol and TCP that lead to unfairness for certain TCP connections. With the introduction of a head-of-line timer to avoid the blocking of the "slow start" mechanism of TCP, fairness can be guaranteed. Another problem arising from the optical node architecture are reorderings of "Jumbo" frames. These lead to spurious retransmissions of TCP segments. A discussion of possibilities to make TCP robust against packet reorderings concludes the chapter. At last we give an outlook on the design of large networks based on PrimeNets. Every AWG-based multihop network can be seen as a permutation or Cayley graph. This family of graphs incorporates many of known regular graphs, such as the ring, the hypercube, or the star graph

All-optical LAN architectures based on Arrayed Waveguide Grating Multiplexers

The paper presents optical LAN topologies which are made possible using an Arrayed Waveguide Grating Multiplexer (AWGM) instead of a passive star coupler to interconnect stations in an all-optical LAN. Due to the collision-free nature of an AWGM it offers the n-fold bandwidth compared to the star coupler. Virtual ring topologies appear (one ring on each wavelength) if the number of stations attached to the AWGM is a prime number. A method to construct larger networks using Cayley graphs is shown. An access protocol to avoid collisions on the proposed network is outlined. 1. INTRODUCTION All optical communication has been investigated in the LAN area for a number of years. Most attempts to make use of the high potential of Wave Division Multiplexing relied on a physical star topology that employed a passive star coupler as a broadcast medium. 1 Other projects 2 favor a physical ring topology with a fixed assignment of the wavelengths. Whenever optical star couplers are being used,..

Partial offloading of OpenFlow rules on a traditional hardware switch ASIC

OpenFlow represents a new powerful paradigm that combines the flexibility of the software with the efficiency of a programmable hardware switch. However, such an approach is currently reserved for new hardware devices, specifically engineered for this paradigm. This paper presents our experience and findings about selectively offloading OpenFlow rules into a non-OpenFlow compatible hardware switch silicon, which enables existing (legacy) hardware ASICs to become compatible with the SDN paradigm. We describe our solution that transparently offloads the portion of OpenFlow rules supported by the hardware while keeping in software the remaining ones, and that is able to support the presence of multiple hardware tables although with limited capabilities in terms of matches and actions. Moreover, we illustrate the design choices used to implement all the basic functionalities required by the OpenFlow protocol (e.g., packet-in, packet-out messages) and then we demonstrate the considerable advantage in terms of performance that can be obtained by performing switching in hardware, while maintaining an SDN-type ability to program and to instantiate desired network operations from a central controlle