9,332 research outputs found
The Road Ahead for Networking: A Survey on ICN-IP Coexistence Solutions
In recent years, the current Internet has experienced an unexpected paradigm
shift in the usage model, which has pushed researchers towards the design of
the Information-Centric Networking (ICN) paradigm as a possible replacement of
the existing architecture. Even though both Academia and Industry have
investigated the feasibility and effectiveness of ICN, achieving the complete
replacement of the Internet Protocol (IP) is a challenging task.
Some research groups have already addressed the coexistence by designing
their own architectures, but none of those is the final solution to move
towards the future Internet considering the unaltered state of the networking.
To design such architecture, the research community needs now a comprehensive
overview of the existing solutions that have so far addressed the coexistence.
The purpose of this paper is to reach this goal by providing the first
comprehensive survey and classification of the coexistence architectures
according to their features (i.e., deployment approach, deployment scenarios,
addressed coexistence requirements and architecture or technology used) and
evaluation parameters (i.e., challenges emerging during the deployment and the
runtime behaviour of an architecture). We believe that this paper will finally
fill the gap required for moving towards the design of the final coexistence
architecture.Comment: 23 pages, 16 figures, 3 table
OSHI - Open Source Hybrid IP/SDN networking (and its emulation on Mininet and on distributed SDN testbeds)
The introduction of SDN in IP backbones requires the coexistence of regular
IP forwarding and SDN based forwarding. The former is typically applied to best
effort Internet traffic, the latter can be used for different types of advanced
services (VPNs, Virtual Leased Lines, Traffic Engineering...). In this paper we
first introduce the architecture and the services of an "hybrid" IP/SDN
networking scenario. Then we describe the design and implementation of an Open
Source Hybrid IP/SDN (OSHI) node. It combines Quagga for OSPF routing and Open
vSwitch for OpenFlow based switching on Linux. The availability of tools for
experimental validation and performance evaluation of SDN solutions is
fundamental for the evolution of SDN. We provide a set of open source tools
that allow to facilitate the design of hybrid IP/SDN experimental networks,
their deployment on Mininet or on distributed SDN research testbeds and their
test. Finally, using the provided tools, we evaluate key performance aspects of
the proposed solutions. The OSHI development and test environment is available
in a VirtualBox VM image that can be downloaded.Comment: Final version (Last updated August, 2014
Irreversible flow of vortex matter: polycrystal and amorphous phases
We investigate the microscopic mechanisms giving rise to plastic depinning
and irreversible flow in vortex matter. The topology of the vortex array
crucially determines the flow response of this system. To illustrate this
claim, two limiting cases are considered: weak and strong pinning interactions.
In the first case disorder is strong enough to introduce plastic effects in the
vortex lattice. Diffraction patterns unveil polycrystalline lattice topology
with dislocations and grain boundaries determining the electromagnetic response
of the system. Filamentary flow is found to arise as a consequence of
dislocation dynamics. We analize the stability of vortex lattices against the
formation of grain boundaries, as well as the steady state dynamics for
currents approaching the depinning critical current from above, when vortex
motion is mainly localized at the grain boundaries. On the contrary, a
dislocation description proves no longer adequate in the second limiting case
examined. For strong pinning interactions, the vortex array appears completely
amorphous and no remnant of the Abrikosov lattice order is left. Here we obtain
the critical current as a function of impurity density, its scaling properties,
and characterize the steady state dynamics above depinning. The plastic
depinning observed in the amorphous phase is tightly connected with the
emergence of channel-like flow. Our results suggest the possibility of
establishing a clear distinction between two topologically disordered vortex
phases: the vortex polycrystal and the amorphous vortex matter.Comment: 13 pages, 16 figure
Coexistence between fluid and crystalline phases of proteins in photosynthetic membranes
Photosystem II (PSII) and its associated light-harvesting complex II (LHCII)
are highly concentrated in the stacked grana regions of photosynthetic
thylakoid membranes. Within the membrane, PSII-LHCII supercomplexes can be
arranged in disordered packings, ordered arrays, or mixtures thereof. The
physical driving forces underlying array formation are unknown, complicating
attempts to determine a possible functional role for arrays in regulating light
harvesting or energy conversion efficiency. Here we introduce a coarse-grained
model of protein interactions in coupled photosynthetic membranes, focusing on
just two particle types that feature simple shapes and potential energies
motivated by structural studies. Reporting on computer simulations of the
model's equilibrium fluctuations, we demonstrate its success in reproducing
diverse structural features observed in experiments, including extended
PSII-LHCII arrays. Free energy calculations reveal that the appearance of
arrays marks a phase transition from the disordered fluid state to a
system-spanning crystal, which can easily be arrested by thermodynamic
constraints or slow dynamics. The region of fluid-crystal coexistence is broad,
encompassing much of the physiologically relevant parameter regime. Our results
suggest that grana membranes lie at or near phase coexistence, conferring
significant structural and functional flexibility to this densely packed
membrane protein system.Comment: 11 pages, 5 figure
Transport Protocols for Data Center Communication
Data centers are becoming more and more important since there is a number of services covered especially by them. At the same time it is reasonable to maintain the costs of data centers low from a number of perspectives.
To this end, one could propose a number of changes in the data center environment. While there is a number of studies that focus on different aspects of the data center environment, one of the most important factors that can be studied and changed is the transport protocol used in the data center environment. This change will have an impact on a number of factors in the data centers.
For the purpose of this thesis a number of transport protocols were studied, starting from the broadly used TCP to a number of especially designed for data centers ones. These variations were studied for the changes they impose and the positive results they bring.
At the same time the significance of DCTCP, the most extensively studied and deployed data center environment protocol was made apparent and the positive results from its deployment. This study outlines the necessity to know its behavior while coexisting with TCP as well since its deployment in the wide Internet would bring positive results for latency, losses and buffer queues minimization.
To this end, the protocol was studied by emulating network behavior in Mininet network emulator and it was found out that its coexistence with TCP is possible without the TCP traffic starving as long as some parameters settings are followed
Building Programmable Wireless Networks: An Architectural Survey
In recent times, there have been a lot of efforts for improving the ossified
Internet architecture in a bid to sustain unstinted growth and innovation. A
major reason for the perceived architectural ossification is the lack of
ability to program the network as a system. This situation has resulted partly
from historical decisions in the original Internet design which emphasized
decentralized network operations through co-located data and control planes on
each network device. The situation for wireless networks is no different
resulting in a lot of complexity and a plethora of largely incompatible
wireless technologies. The emergence of "programmable wireless networks", that
allow greater flexibility, ease of management and configurability, is a step in
the right direction to overcome the aforementioned shortcomings of the wireless
networks. In this paper, we provide a broad overview of the architectures
proposed in literature for building programmable wireless networks focusing
primarily on three popular techniques, i.e., software defined networks,
cognitive radio networks, and virtualized networks. This survey is a
self-contained tutorial on these techniques and its applications. We also
discuss the opportunities and challenges in building next-generation
programmable wireless networks and identify open research issues and future
research directions.Comment: 19 page
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