1,720,958 research outputs found
Kathará: A Lightweight Network Emulation System
No full textIn computer networks, tests to ensure the correct behaviour of network equipment or protocols are often required. Because of the high cost of physical hardware, these tests are always performed in a virtual environment. Kathará is a network emulation system which accurately reproduces the behaviour of a real system. It can exploit several virtualization technologies leveraging on its modularity. Lately, Kathará has been rewritten to overcome some implementation limitations and performance issues. This paper presents the Kathará model and its new architecture, demonstrating its value, comparing its scalability and performance with Netkit (another state-of-the-art tool for network emulation) and with the previous version of Kathará
MRT: A Fast Multi-Threaded MRT Parser
No full textBGP is the inter-domain routing protocol of the Internet. BGP routers exchange BGP Updates, and adjust their routing table to reflect changes in the network. A wide variety of research and operational projects leverage on massive processing of BGP Updates, so it is crucial to analyse such data in the most efficient way. Hence, different MRT parsers have been developed. Most of them are unsuitable for big data analyses due to various limitations. In this paper, we present MRT, a multi-threaded MRT parser library written in C. We show its architecture, a performance comparison with other MRT parsers, and its possible integration into a data processing pipeline
VFTGen: A Tool to Perform Experiments in Virtual Fat Tree Topologies
No full textData centers are a critical part of the Internet infrastructure. In fact, most of the relevant online services are hosted in a data center. Data center networks are complex, since they are characterized by a high density architecture and by a high level of redundancy. Fat tree topologies are currently the most used in hyperscale data centers. Performing tests in such topologies would be unfeasible, because of the high costs of the required equipment and due to the involvement of human resources. This would limit the automation and reproducibility of tests, leading to a more error-prone testing pipeline. This paper presents VFTGen, a tool that, leveraging on the virtualization and the Software Defined Data Center concepts, automatically builds, deploys and configures arbitrary fat tree topologies in a virtual environment. We demonstrate the ease of use of the tool and its value as a support to the study or the development of networking protocols for fat trees
A High-Speed Stateful Packet Processing Approach for Tbps Programmable Switches
No full textHigh-speed ASIC switches hold great promise for offloading complex packet processing pipelines directly in the high-speed data-plane. Yet, a large variety of today's packet processing pipelines, including stateful network functions and packet schedulers, require storing some (or all the) packets for short amount of times in a programmatic manner. Such a programmable buffer feature is missing on today's high-speed ASIC switches. In this work, we present RIBOSOME, a system that extends programmable switches with external memory (to store packets) and external general-purpose packet processing devices such as CPUs or FPGAs (to perform stateful operations). As today's packet processing devices are bottlenecked by their network interface speeds, RIBOSOME carefully transmits only the relevant bits to these devices. RIBOSOME leverages spare bandwidth from any directly connected servers to store the incoming payloads through RDMA. Our evaluation shows that RIBOSOME can process 300G of traffic through a stateful packet processing pipeline (e.g., firewall, load balancer, packet scheduler) by running the pipeline logic on a single server equipped with one 100G interface
Achieving Best-path Selection at Line Rate through the SRv6 Live-Live Behavior
No full textThe network programming model of the Segment Routing (SRv6) architecture offers the possibility to define new functions aiming at improving the network performance. In this paper we introduce SRv6 Live-Live, a new behavior for the SRv6 data plane. SRv6 Live-Live is based on two primitives: i) traffic duplication, performed at the ingress node, and ii) the traffic de-duplication, executed at the egress node. The proposed behavior is suitable for the service provisioning of traffic flows having stringent requirements in terms of reliability, low delay and high throughput. Our preliminary performance evaluation, conducted in an emulated environment and realized by using a prototype implementation based on P4, shows that SRv6 Live-Live enhances the performance of the selected traffic flows in challenging network scenarios, characterized by high level of packet corruption/loss and large values of bandwidth-delay products
Sibyl: A Framework for Evaluating the Implementation of Routing Protocols in Fat-Trees
No full textSeveral data centers adopt fat-tree topologies, where high bisection bandwidth is achieved by interconnecting commodity hardware and by using specific routing solutions. These solutions, which include protocol implementations and configurations, are difficult to evaluate and test both for the density of fat-trees and for the complexity of the protocols. Also, since most issues show up only when a fault happens, it is unfeasible to perform such tests in a production environment. Additionally, the lack of standard testing procedures motivates an effort in developing solutions for such a critical task. In this paper, we propose a methodology devised for testing fat-tree routing protocol implementations. It adopts a wall-clock independent method to establish metrics, which permits normalizing the results of different routing protocol implementations independently from the execution environment. The methodology is implemented by Sibyl, a software framework developed to perform repeatable tests on arbitrary fat-tree topologies automatically. Sibyl also provides a set of tools to analyze the results and investigate implementation behaviors. We evaluate the methodology and Sibyl in three use cases. Such use cases witness a wide spectrum of situations where Sibyl is effective for analyzing, comparing, developing, and debugging routing protocol implementations
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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