1,720,961 research outputs found
Robust and Resilient GNSS Synchronization of LEO Satellites for Space-based Aircraft Multilateration
No full textThis paper aims at developing a robust and resilient synchronization framework for Low Earth Orbit (LEO) satellites based on the combination of GNSS and Precision Time Protocol (PTP) via inter-satellite link. The satellite synchronization is needed to enable precise aircraft tracking in areas without radar coverage, by leveraging Automatic Dependent Surveillance-Broadcast (ADS-B) signals and advanced localization algorithms, exploiting Time Of Arrival (TOA), Frequency Of Arrival (FOA), and Angle Of Arrival (AOA). An Extended Kalman Filter (EKF) corrects onboard clock errors in real time, while detecting and mitigating anomalies or cyber-attacks like GNSS jamming, spoofing or denial of service. Nanosecond accuracy under nominal and disrupted conditions is obtained, significantly enhancing safety and reliability of the tracking system
DIDA: distributed in-network intelligent data plane for machine learning applications
No full textRecent advances in network switch designs have enabled machine learning inference directly within the switch at line speed. However, hardware constraints limit switches capabilities of tracking stateful features essential for accurate inference, as the demand for these features grows rapidly with line rates. To address this, we propose DIDA, a distributed in-network machine learning approach. In DIDA, feature extraction occurs at the host, features are transmitted via in-band telemetry, and inference is performed on the switches. In this paper, we evaluate the effectiveness and efficiency of this architecture. We examine its impact on network bandwidth, CPU and memory usage at the host, and its robustness across different feature sets and deep neural network classifications
Supporting future internet services with extensible in-band processing (EIP)
No full textNetworking architectures need to evolve to support the requirements of future Internet services and 6G networks. In this paper we propose an evolutionary solution that extends the IPv6 networking architecture fully supporting the needs of future services, called Extensible In-band Processing (EIP). The EIP solution considers a feature-rich networking layer, in which hosts and routers can cooperate by reading and writing the EIP information in the IPv6 packet headers, to support a number of use cases. Example use case are: advanced monitoring, semantic routing, deterministic networking, slicing and so on. This list of use cases is not exhaustive, as a key feature of EIP is to be extensible for the support of new use cases. In the paper we describe the initial design of the EIP header and protocol mechanisms. We have released an open source prototype implementation of EIP for Linux OS, based on the eBPF packet processing framework. The implementation includes tools for the generation of test EIP packets and for the protocol dissection of packets. A replicable testbed provides an early demonstration of the advanced monitoring and semantic routing use cases
High Performance Delay Monitoring for SRv6-Based SD-WANs
No full textSoftware-Defined Wide Area Networks (SD-WANs) are used to provide services to enterprises with geographically dispersed locations in a flexible and efficient way. We focus on SD-WAN services based on the Segment Routing over IPv6 (SRv6) technology. Performance Monitoring solutions are needed in SD-WANs to detect performance degradation and outages, and optimize network operations. In this paper, we describe a high performance solution for end-to-end delay monitoring for SRv6 based SD-WAN services. The proposed solution leverages the Simple Two-way Active Measurement Protocol (STAMP) to monitor the delay of an SRv6 path between two nodes called STAMP Session-Sender and Session-Reflector. We describe three implementations of the STAMP Session-Sender and Session-Reflector for a Linux software router and compare their performance. In particular, two implementations are based on user space processing and one is based on eBPF. The results show that the eBPF-based implementation outperforms the user space implementations and has a negligible impact on the forwarding capacity of the Linux software router
Composing eBPF Programs Made Easy With HIKe and eCLAT
No full textWith the rise of the Network Softwarization era, eBPF has become a hot technology for efficient packet processing on commodity hardware. However the development of custom eBPF solutions is a challenging process that requires highly qualified human resources. Indeed, in eBPF, it is difficult to devise truly modular applications since the development model does not favour the use of pre-compiled functions and libraries. In addition, for safety purposes, each eBFF program must pass a binary code verifier of the Linux kernel, which may increase the difficulty of the development process. To overcome such difficulties and enable a new development model, in this paper we propose the eCLAT framework with the goal to lower the learning curve of engineers by re-using eBPF code in a programmable way. eCLAT offers a high level programming abstraction to eBPF based network programmability, allowing a developer to create custom application logic with no need of understanding the complex details of regular eBPF programming. A developer can write eCLAT scripts in a python-like language to compose eBPF programs. To support such abstraction at the eBPF level, we created an eBPF framework called HIKe which brings code reuse and modularity in eBPF. The eCLAT/HIKe solution does not require any kernel modification. The new development model is tested through two concrete examples and compared with other proposed frameworks in the eBPF world
Optimal design of 5G superfluid networks: Problem formulation and solutions
No full textThe forthcoming 5G technology foresees the exploitation of solutions able to increase both the flexibility and the scalability of the network. In line with the current trend of softwarization, in this work we face the problem of designing a 5G network from the outcome of the Horizon 2020 project Super-fluidity. The core of the project is the definition of a 5G converged architecture based on virtual entities, called Reusable Functional Blocks (RFBs), which can be run on different HardWare (HW) and SoftWare (SW) execution environments. The exploitation of RFBs allows to achieve the required level of flexibility required by 5G. After optimally formulating the problem of minimizing the total installation costs of a SuperFluid network composed of RFBs and physical 5G nodes, we propose a new algorithm, called SFDA, to practically tackle the problem. Our results, obtained over a representative case study, show that SFDA is able to solve the problem in a reasonable amount of time, returning solutions very close to the optimum. In addition, we clearly show the trade offs that emerge between the need of providing a service level to users (in terms of downlink traffic or coverage) and the total costs incurred to install the elements of the network
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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