1,721,051 research outputs found
End-to-End Performance of Heterogeneous Multi-EPON/OBS Networks
No full textIn this paper end-to-end performance is evaluated when multiple high-speed access networks, based on the Ethernet Passive Optical Network (EPON) technology, are interconnected through an Optical Burst Switching (OBS) core network. The inter-working unit, or edge node, between these two different networks is properly studied and discussed. A time-based burst assembly algorithm is assumed, which is analyzed and dimensionedto cope with multiple EPONs. The role of a key parameter,such as the EPON cycle time used in the multiple access scheme,is assessed. Transport layer performance of the multi-EPON/OBSnetwork is evaluated through simulations with ns2. Results showthat the relationship between the EPON cycle time and the burstassembly time has a fundamental role and requires proper tuningto optimize, e.g., the TCP throughput
Analytical model for anycast service provisioning in data center interconnections
No full textThis paper presents an analytical model to evaluate the performance of an optical wavelength-routed network for inter- and intra-data center interconnection, designed to work according to the cloud computing paradigm. Such a scenario calls for anycast routing of service requests to find a network path that best suits both connectivity and IT resource requirements. The analytical model is based on conventional queuing theory for loss systems combined with an ad-hoc combinatorial analysis of the anycast service alternatives. The model presented here is meant to provide engineering guidelines for data center interconnection networks supporting the cloud paradigm, in particular in terms of performance and cost of resource distribution
Transport Layer Performance of Hybrid Networks Combining Multiple EPONs and OBS
No full textIn this paper the performance of a hybrid opticalnetwork composed of multiple Ethernet Passive Optical Networks(EPONs) at the access connected to an Optical Burst Switching(OBS) core is evaluated. The EPONs make use of the IPACTalgorithm to manage the upstream transmissions, whereas theOBS edge node employs a time-based assembly scheme forburst aggregation. This leads to interoperability issues betweenaccess and core which are investigated in this paper. Thehybrid network scalability is proved by assessing the transportlayer performance with different numbers of EPONs served bythe same burst assembler and different numbers of OpticalNetwork Units (ONUs) per EPON. The impact of the maindesign parameters affecting the interaction between EPONs andOBS is estimated. The transport layer performance is evaluatedconsidering heterogeneous traffic flows by simulating both TCPand UDP sources
Software Defined Wide Area Networking (SD-WAN)
No full textA reliable Wide Area Network (WAN) has become a necessity for businesses
to transmit critical data across multiple branches and to increase their revenues. Many
solutions and dierent network structures have been proposed over years such as leased
lines, Frame Relay or Multi-Protocol Label Switching Virtual Private Networks (MPLS
VPN). Each solution is intended to be better than its predecessors in terms of reliabil-
ity and Quality of Service (QoS). Software-Dened Wide Area Networking (SD-WAN)
is an emerging paradigm that introduces the advantages of software dened networking
(SDN) into enterprise networking. SD-WAN can support dierentiated services over pub-
lic WAN by dynamically changing the
ow forwarding rules over an overlay network based
on monitoring data and service requirements. Thanks to these capabilities, it is possible to
overcome high cost of guaranteed QoS services such as MPLS. Most of the SD-WAN so-
lutions commercially available today are based on proprietary controllers and proprietary
Customer Provider Edge (CPE) devises. In this chapter, we present an implementation
of SD-WAN based on open source components such as OpenDaylight SDN controller and
Open Virtual Switch (OvS). This work targets the monitoring features of an SD-WAN
solution and explores active and passive monitoring approaches to understand their ad-
vantages and limitations. Our implementation provides an overlay WAN with controlled
performance in terms of delay and losses over low-cost Internet connectivity
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
TCP Performance in Multi-EPON Access Networks under Different Optical Core Switching Paradigms
No full textIn this paper the end-to-end TCP performance of a hybrid network composed of multiple Ethernet Passive Optical Networks (EPONs) in the access segment connected to the same edge node of a core network is evaluated.
Three possible core network paradigms are considered: Optical Circuit Switching (OCS), Optical Burst Switching (OBS) and Optical Packet Switching (OPS). TCP performance is evaluated through simulations with ns-2.
The hybrid network scalability is assessed by varying the number of EPONs connected to the same edge node and the number of Optical Network Units (ONUs) per EPON. Interoperability issues between access and core are investigated and the impact of the most important network parameters is highlighted. The three transfer modes considered for the core network are properly compared under different input conditions, discussing the related trade-offs that may lead to the most suitable choice based on the specific
application scenario. Finally, some design issues are investigated with reference to emerging Long-Range EPON (LR-EPON) solutions
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
Network resource allocation in data center interconnection with anycast service provisioning
No full textThe joint management of IT and network resources is a key aspect for dynamic inter-data center interconnection networks designed to work according to the cloud computing paradigm. Such a scenario calls for the anycast routing of service requests to find a data channel that best suits both connectivity and IT resource requirements. This paper presents different network resource allocation and release policies across an inter-data center interconnection network aimed at a balanced accommodation of network resources to improve performance. Such policies are evaluated and compared in terms of service set-up blocking probability considering also configuration latency of real network devices that play a significant role along with network bandwidth availability across the network. Results show that the best choice is to release network resources as soon as possible, even though this means increasing the service blocking due to network reconfiguration latency
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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