1,720,968 research outputs found
Partial offloading of OpenFlow rules on a traditional hardware switch ASIC
No full textOpenFlow 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
User-specific Network Service Functions in an SDN-enabled Network Node
Full text linkNetwork Functions Virtualization can enable each user (tenant) to define his desired set of network services, called (network) service graph. For instance, a User1 may want his traffic to traverse a firewall before reaching his terminal, while a User2 may be interested in a different type of firewall and in a network monitor as well. This paper presents a prototype of an SDN-enabled node that, given a new user connected to one of its physical ports, it is able to dynamically instantiate the user’s network service graph and force all his traffic to traverse the proper set of network functions
A datapath-centric virtualization mechanism for OpenFlow networks
No full textAbstract:
The adoption of a robust and scalable network virtualization framework is a key requirement in order to make the vision of a shareable network infrastructure a reality. To this aim, one of the most suitable approaches is the one which takes advantage of the emerging paradigm of Software-Defined Networking (SDN) and OpenFlow, its de-facto standard. Several virtualization frameworks have been proposed in the last few years, however, they are either based on proxy-based solutions that raises scalability and robustness issues (FlowVisor), or they rely 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. This paper presents a novel OpenFlow-based network virtualization mechanism exploiting a recent open-source data path project named extensible Data path Daemon (xDPd), the proposed multi-platform data path is based on a robust distributed virtualization architecture that is able to run on multi-version OpenFlow switch network scenarios, has a minimal overhead from a performance point of view and can be easily ported on several hardware platforms via xDPd libraries
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Signalling-Based Architectures for Impairment-Aware Lightpath Set-Up in GMPLS Networks
No full textThis paper explores the solution space for extending the signaling protocol of a GMPLS control plane for an impairment-aware path setup in transparent optical networks. Four combinations of routing and optical feasibility checking architectures based on modifications of RSVP-TE are proposed and studied. Simulation results show that a combination of hop- by-hop routing and feasibility check can be considered as a good compromise both in term of blocking probability and limited impact on the control plane. The slightly higher lightpath set-up time compared to other architectures can be tolerated especially considering the impact on the RSVP protocol current behavior as well as its independence from parameters strictly related to the network properties and topology
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