1,720,962 research outputs found
Design and development of a DS-TE experimental testbed with P2MP LSP support
No full textNowadays, many IP backbone networks adopt separate control and forwarding planes for unicast and multicast traffic flows. Indeed, while MPLS (Multiprotocol Label Switching) is widely deployed for unicast trafile, IP multicast is the only available solution for the delivery of "one-to-many" traffic flows. With P2MP LSPs (Point-to-Multipoint Label Switched Paths) support, a unified control and forwading plane may be devised. Such a reduction in the number of protocols used in the core of the network as well as in the number of encapsulations in the data plane, results in simplified network operations. The paper discusses the design and the development of the control and data planes extensions needed to provide P2MP LSP support in an MPLS network. In particular, such signalling and forwarding mechanisms have been implemented in a network testbed based on open-source routers. Finally, tests have been performed to assess the new mechanisms from both an operational and performance point-of-view
Experimental Validation of SLAs in Operational Networks through Hash-based Packet Sampling
No full textIn operational networks, services are delivered according to specific Service Level Agreements (SLAs). To ensure the SLAs stipulated with the users, providers make use of traffic monitoring and measurement tools controlling their highspeed IP networks. In order to improve the scalability of the measurement systems, techniques which allow to reduce the total amount of data to be collected and processed are currently being standardized in the IETF Packet Sampling (PSAMP) Working Group. Among packet sampling techniques, hash-based one is the only capable of providing a feasible framework to monitor One-Way Delays (OWDs). This paper is focused on the experimental validation of SLAs conformance in operational networks using hash-based packet sampling techniques. The results presented hereafter are obtained from the analysis of traffic traces collected at two different points of operational networks. Such results are fundamental to validate the whole hash-based packet sampling framework, because they complement the already available results on the uniformity of distribution, computation speed and statistical properties of the hash functions calculated by using single point traces
Dynamic resource configuration in DiffServ networks: Control plane mechanisms and performance evaluation of a traffic control API
No full textVoice, video and multimedia applications are sensitive to the QoS provided by the underlying IP network. The DiffServ architecture offers a set of QoS mechanisms for IP networks. The "binding" of the applications QoS needs with the QoS features offered by the DiffServ networks is still an open problem. The simplest approach is to have a static configuration of QoS and therefore no direct interaction in the control plane between applications and QoS. We consider the advanced scenario, where the QoS mechanisms can be dynamically configured to follow the applications' need. For this scenario, a set of control plane interfaces needed for a whole end-to-end QoS architecture is defined. At the lower level, an internal interface ("Application Programming Interface"-API) in the QoS router is considered. This interface provides access to the DiffServ QoS mechanism available in a router and is used by the control logic running in the router itself. Then a QoS signaling protocol is considered, that allows external QoS clients to dynamically access the QoS services provided by the network. Finally the interaction of a session level signaling protocol (i.e., the SIP for IP telephony) with the QoS protocol is defined. A testbed implementation of the proposed architecture and a set of performance tests on the internal QoS API are reported. (C) 2003 Elsevier B.V. All rights reserved
A soft real-time measurement system for Diffserv/MPLS edge routers
No full textThe paper presents the architecture of a measurement system designed to reside into DiffServ/MPLS
Linux based routers. The goal of this research is to develop an open source software product to be used
for management purposes and to be integrated in the network control plane in order to automate resource
allocation, admission control and Traffic Engineering functionalities. The system is designed to be flexible,
configurable and modular and each module has been implemented in order to minimize the impact of the
system itself on the traffic dynamics. The output of the system is a sequence of measurements that report
the amount of per-PHB and per-LSP traffic offered to the router over a configurable time window. The
system allows to perform prediction on the future traffic activity as well as trigger asynchronous threshold
crossing events. The system has proven to be reliable as it passed several functional tests. Preliminary
experimental results have shown that the output of the system accurately captures the traffic patterns offered
to the router
SIP originated dynamic resource configuration in DiffServ networks: SIP/COPS/traffic control mechanisms
No full textVoice, video and multimedia sessions are applications sensitive to the QoS provided by the underlying IP network. Therefore a lot of interest is currently devoted to the interaction of application level protocols with the QoS mechanism in IP networks. Among them SIP is currently having a lot of attention as a protocol for session signaling over the Internet. This work will describe an enhancement to SIP protocol for the interworking with a QoS enabled IP network. The proposed mechanism is simple and it fully preserves backward compatibility and interoperability with current SIP applications. Moreover the paper describes the application of this mechanism to a particular QoS enabled IP network, which implements DiffServ as transport mechanisms (the DiffServ mechanisms are obtained by means of Traffic Control functionalities with the TCAPI software libraries) and modified COPS clients for resource admission control. A test-bed implementation on Linux PCs of the proposed solutions is finally described
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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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