Network Traffic Processing with PFQ

This paper presents Packet Family Queue (PFQ), a high-performance framework for packet processing designed to flexibly handle network applications parallelism and making traffic processing safe and easy. PFQ is an open-source module for the Linux kernel that combines software-accelerated packet I/O to in-kernel early stage packet processing and fine-grained distribution to network applications and physical devices. PFQ does not require any modification to network device drivers and exposes programming interfaces to multi-threaded applications natively designed to run on top of it, as well as to legacy monitoring tools using the pcap library. The results show that the flexibility and the backward compatibility provided by PFQ do not impact its processing performance that, in fact, reaches line rate figures in the cases of pure speed tests and real practical monitoring use cases on 10+ Gb/s links

Randomized Packet Filtering through Specialized Partitioning of Rulesets

A key issue in high speed traffic processing is to immediately detect potentially interesting packets. At very high speed, this operation is particularly crucial as filtering packets close to the wire relieves real applications from handling large volumes of (uninteresting) data. This paper proposes a fast and randomized approach to packet filtering based on partitioning rule databases for their storage in fast and compact Bloom filters that can be placed in fast cache memory. Database partitioning is obtained by a specially tailored clustering algorithm and the results show that even large rulesets can be divided into a limited number of partitions and accommodated in reasonably small Bloom filters

Enif-lang: A specialized language for programming network functions on commodity hardware

The maturity level reached by today’s commodity platforms makes even low-cost PCs viable alternatives to dedicated hardware to implement real network functions without sacrificing performance. Indeed, the availability of multi-core processing packages and multi-queue network interfaces that can be managed by accelerated I/O frameworks, provides off-the-shelf servers with the necessary power capability for running a broad variety of network applications with near hardware-class performance. At the same time, the introduction of the Software Defined Networks (SDN) and the Network Functions Virtualization (NFV) paradigms call for new programming abstractions and tools to allow this new class of network devices to be flexibly configured and functionally repurposed from the network control plane. The paper presents the ongoing work towards Enif-Lang (Enhanced Network processIng Functional Language), a functional language for programming network functions over generic middleboxes running the Linux operating system. The language addresses concurrent programming by design and is targeted at developing simple stand-alone applications as well as pre-processing stages of packet elaborations. Enif-Lang is implemented as a Domain Specific Language embedded in the Haskell language and inherits the main principles of its ancestor, including the strong typedness and the concept of function compositions. Complex network functions are implemented by composing a set of elementary operations (primitives) by means of a compact yet expressive language grammar. Throughout the paper, the description of the design principles and features of Enif-Lang are accompanied by examples and use cases. In addition, a preliminary performance assessment is carried out to prove the effectiveness of the language for developing practical applications with the performance level required by 5G systems and the Tactile Internet

Lamellar ordering, droplet formation and phase inversion in exotic active emulsions

We study numerically the behaviour of a mixture of a passive isotropic fluid and an active polar gel, in the presence of a surfactant favouring emulsification. Focussing on parameters for which the underlying free energy favours the lamellar phase in the passive limit, we show that the interplay between nonequilibrium and thermodynamic forces creates a range of multifarious exotic emulsions. When the active component is contractile (e.g., an actomyosin solution), moderate activity enhances the efficiency of lamellar ordering, whereas strong activity favours the creation of passive droplets within an active matrix. For extensile activity (occurring, e.g., in microtubule-motor suspensions), instead, we observe an emulsion of spontaneously rotating droplets of different size. By tuning the overall composition, we can create high internal phase emulsions, which undergo sudden phase inversion when activity is switched off. Therefore, we find that activity provides a single control parameter to design composite materials with a strikingly rich range of morphologies.Comment: 15 pages: Manuscprit (4 figures) and SI (11 figures

Packet Fan-Out Extension for the pcap Library

The large availability of multi-gigabit network cards for commodity PCs requires network applications to potentially cope with high volumes of traffic. However, computation intensive operations may not catch up with high traffic rates and need to be run in parallel over multiple processing cores. As of today, the vast majority of network applications - e.g., monitoring and IDS systems - are still based on the pcap library interface which, unfortunately, does not provide the native multi-core support, even though the current underlying capture technologies do. This paper introduces a novel version of the pcap library for the Linux operating system that enables transparent application level parallelism. The new library supports fan-out operations for both multi-threaded and multi-process applications, by means of extended API as well as by a declarative grammar for configuration files, suitable for legacy applications. In addition, the library can transparently run on top of the standard Linux socket as well as on other accelerated active engines. Performance evaluation has been carried out on a multi-core architecture in pure capture tests and in more realistic use cases involving monitoring applications such as Tstat and Bro, with standard Linux socket as well as PFRING and PFQ accelerated engines

Undoped and Fe-Doped Anatase/Brookite TiO2 Mixed Phases, Obtained by a Simple Template-Free Synthesis Method: Physico-Chemical Characterization and Photocatalytic Activity towards Simazine Degradation

For the first time, Fe-doping (0.05, 1.0, and 2.5 wt.% Fe) was performed on a high-surface-area anatase/brookite TiO2 by adopting a simple template-free sol-gel synthesis followed by calcination at a mild temperature. The powders’ textural and surface properties were characterized by following a multi-technique approach. XRD analysis showed that the anatase/brookite ratio slightly varied in the Fe-doped TiO2 (from 76.9/23.1 to 79.3/22.7); Fe doping noticeably affected the cell volume of the brookite phase, which decreased, likely due to Fe3+ ions occupying interstitial positions, and retarded the crystallite growth. N2 sorption at −196 °C showed the occurrence of samples with disordered interparticle mesopores, with an increase in the specific surface area from 236 m2 g−1 (undoped TiO2) to 263 m2 g−1 (2.5 wt.% Fe). Diffuse Reflectance UV-Vis spectroscopy showed a progressive decrease in the bandgap energy from 3.10 eV (undoped TiO2) to 2.85 eV (2.5 wt.% Fe). XPS analysis showed the presence of some surface Fe species only at 2.5 wt.% Fe, and accordingly, the ζ-potential measurements showed small changes in the pH at the isoelectric point. The photocatalytic degradation of simazine (a persistent water contaminant) both under UV and simulated solar light was performed as a probe reaction. Under UV light, Fe-doping improved simazine degradation in the sample at 0.05 wt.% Fe, capable of degrading ca. 77% simazine. Interestingly, the undoped TiO2 was also active both under UV and 1 SUN. This is likely due to the occurrence of anatase/brookite heterojunctions, which help stabilize the photogenerated electrons/holes

Diode-pumped passively mode-locked Yb:YLF laser.

We demonstrate passive mode-locking by means of a semiconductor saturable-absorber mirror in a diode-pumped Yb:YLF laser. We present crystal growth process, spectroscopic measurements, and investigation of mode-locking performance. Pulse trains with minimum duration of 196 fs, average power of 54 mW and a repetition rate of 55 MHz were obtained. The optical spectrum, centered at 1028 nm, has a 7.1-nm bandwidth leading to nearly transform-limited pulses. (C) 2008 Optical Society of America

Towards approximate fair bandwidth sharing via dynamic priority queuing

We tackle the problem of a network switch enforcing fair bandwidth sharing of the same link among many TCP-like senders. Most of the mechanisms to solve this problem are based on complex scheduling algorithms, whose feasibility becomes very expensive with today's line rate requirements, i.e. 10-100 Gbit/s per port. We propose a new scheme called FDPA in which we do not modify the scheduler, but instead we use an array of rate estimators to dynamically assign traffic flows to an existing strict priority scheduler serving only few queues. FDPA is inspired by recent advances in programmable stateful data planes. We propose a design that uses primitives common in data plane abstractions such as P4 and OpenFlow. We conducted experiments on a physical 10 Gbit/s testbed, we present preliminary results showing that FDPA produces fairness comparable to approaches based on scheduling

The Road to BOFUSS: The Basic OpenFlow User-space Software Switch

Software switches are pivotal in the Software-Defined Networking (SDN) paradigm, particularly in the early phases of development, deployment and testing. Currently, the most popular one is Open vSwitch (OVS), leveraged in many production-based environments. However, due to its kernel-based nature, OVS is typically complex to modify when additional features or adaptation is required. To this regard, a simpler user-space is key to perform these modifications. In this article, we present a rich overview of BOFUSS, the basic OpenFlow user-space software switch. BOFUSS has been widely used in the research community for diverse reasons, but it lacked a proper reference document. For this purpose, we describe the switch, its history, architecture, uses cases and evaluation, together with a survey of works that leverage this switch. The main goal is to provide a comprehensive overview of the switch and its characteristics. Although the original BOFUSS is not expected to surpass the high performance of OVS, it is a useful complementary artifact that provides some OpenFlow features missing in OVS and it can be easily modified for extended functionality. Moreover, enhancements provided by the BEBA project brought the performance from BOFUSS close to OVS. In any case, this paper sheds light to researchers looking for the trade-offs between performance and customization of BOFUSS.Comment: 24 pages, 7 figures; submitted to Telecommunications Systems journa

In‐hospital and long‐term mortality for acute heart failure: analysis at the time of admission to the emergency department

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