Multiple Physical Links Research Articles

From Atmospheric Waves to Heatwaves: A Waveguide Perspective for Understanding and Predicting Concurrent, Persistent, and Extreme Extratropical Weather

Abstract A notable number of high-impact weather extremes have occurred in recent years, often associated with persistent, strongly meandering atmospheric circulation patterns known as Rossby waves. Because of the high societal and ecosystem impacts, it is of great interest to be able to accurately project how such extreme events will change with climate change, and to predict these events on seasonal-to-subseasonal (S2S) time scales. There are multiple physical links connecting upper-atmosphere circulation patterns to surface weather extremes, and it is asking a lot of our dynamical models to accurately simulate all of these. Subsequently, our confidence in future projections and S2S forecasts of extreme events connected to Rossby waves remains relatively low. We also lack full fundamental theories for the growth and propagation of Rossby waves on the spatial and temporal scales relevant to extreme events, particularly under strongly nonlinear conditions. By focusing on one of the first links in the chain from upper-atmospheric conditions to surface extremes—the Rossby waveguide—it may be possible to circumvent some model biases in later links. To further our understanding of the nature of waveguides, links to persistent surface weather events and their representation in models, we recommend exploring these links in model hierarchies of increasing complexity, developing fundamental theory, exploiting novel large ensemble datasets, harnessing deep learning, and increased community collaboration. This would help increase understanding and confidence in both S2S predictions of extremes and of projections of the impact of climate change on extreme weather events.

The Performance Evaluation of a 3D Torus Network Using Partial Link-Sharing Method in NoC Router Buffer

The high performance network-on-chip (NoC) router using minimal hardware resources to minimize the layout area is very essential for NoC design. In this paper, we have proposed a memory sharing method of a wormhole routed NoC architecture to alleviate the area overhead of a NoC router. In the proposed method, a memory is shared by multiple physical links by using a multi-port memory. In this paper, we have proposed a partial link-sharing method and evaluated the communication performance using the proposed method. It is revealed that the resulted communication performance by the proposed methods is higher than that of the conventional method, and the progress ratio of the 3D-torus network is higher than that of 2D-torus network. It is shown that the improvement of communication performance using partial link sharing method is achieved with slightly increase of hardware cost. Copyright © 2017 The Institute of Electronics, Information and Communication Engineers.

A highly efficient behavioural model of router for network-on-chip with link aggregation

A new method of link aggregation (LAG) in networks-on-chip (NoC) is investigated. This method considerably (by 152 ÷ 300%) increases a network saturation threshold by connection of topologically adjacent routers using of multiple physical links. The authors consider several ways how to improve simulation performance of digital circuits. An algorithm, which illustrates operation of high-performance SystemC model of a NoC router with LAG, is proposed. This paper also includes results of computer simulation of the suggested fast SystemC model and its synthesisable System Verilog counterpart. The results of ModelSim simulation show that usage of proposed SystemC model instead of its System Verilog analogue reduces the duration of simulation in ten times and diminish the required memory in 121 times. Herewith, the prediction error for saturation threshold of NoC does not exceed 6.1%.

A new application‐level link aggregation and its implementation on Android terminals

ABSTRACTLink aggregation bundles multiple physical links on a single virtual link, enabling very high‐speed and large‐capacity data communications. It also enables redundant communications. Several link aggregation methods have been proposed. These methods utilize transport/or lower layer link aggregation. In this paper, a new application‐level link aggregation is proposed and implemented on Android operating system (OS), which is one of the popular OSs for mobile devices such as smartphones and tablet PCs. The proposed application‐level link aggregation method is verified with use of an implemented terminal. Copyright © 2012 John Wiley & Sons, Ltd.

Demonstrating generalized virtual topologies in an openflow network

Network Virtualization (NV) is one of the most promising approaches to enable innovation in today’s network. Generally speaking, NV refers to the possibility of pooling together low–level hardware and software resources belonging to a networked system into a single administrative entity. In such a way network resources could be effectively shared in a transparent way among different logical network instances corresponding to different virtual network topologies. A recent approach toward Network Virtualization has been proposed through FlowVisor [1], whose aim is to leverage on the specific features of an OpenFlow–controlled network [2] to share the same hardware forwarding plane among multiple logical networks. As highlighted by the authors in [1], one of the major limitations of FlowVisor is the inability to establish virtual topologies not restricted by the underpinning physical topology. As a consequence, FlowVisor is unable to provide researchers flexibility in designing their experiments with arbitrary network topologies on a defined physical infrastructure. The architecture presented in Chapter 2 of this paper, called ADVisor (ADvanced FlowVisor), provides the functionalities to overcome the above-mentioned FlowVisor’s limitation by allowing the instantiation of generalized virtual topologies in a OpenFlow network through the implementation of virtual links as aggregation of multiple physical links and OpenFlow-enabled switches. In this demo we will show the configuration of a simple virtual topology performed through a Web-based control framework which allows the reservation of network resources (nodes, links and bandwidth) and the management of virtual resources (virtual links and virtual ports). We will also demonstrate the effective instantiation of the virtual topology by running a synthetic traffic generator application.

100Gb/s Ethernet Inverse Multiplexing Based on Aggregation at the Physical Layer

We propose a packet-based inverse multiplexing method to allow scalable network access with a bigger-pipe physical interface. The method is based on aggregation at the physical layer (APL) that fragments an original packet-flow and distributes the fragments among an adequate numbers of physical links or networks. It allows us to share wavelengths and/or bandwidth resources in optical networks. Its technical feasibility at the speed of newly standardized 100Gb/s Ethernet (100GbE) is successfully evaluated by implementing the inverse multiplexing logic functions on a prototype board. We demonstrate super-high-definition video streaming and huge file transfer by transmitting 100GbE MAC frames over multiple 10GbE physical links via inverse multiplexing.

Impact of Disease-causing SUR1 Mutations on the KATP Channel Subunit Interface Probed with a Rhodamine Protection Assay

The function of the ATP-sensitive potassium (K(ATP)) channel relies on the proper coupling between its two subunits: the pore-forming Kir6.2 and the regulator SUR. The conformation of the interface between these two subunits can be monitored using a rhodamine 123 (Rho) protection assay because Rho blocks Kir6.2 with an efficiency that depends on the relative position of transmembrane domain (TMD) 0 of the associated SUR (Hosy, E., Dérand, R., Revilloud, J., and Vivaudou, M. (2007) J. Physiol. 582, 27-39). Here we find that the natural and synthetic K(ATP) channel activators MgADP, zinc, and SR47063 induced a Rho-insensitive conformation. The activating mutation F132L in SUR1, which causes neonatal diabetes, also rendered the channel resistant to Rho block, suggesting that it stabilized an activated conformation by uncoupling TMD0 from the rest of SUR1. At a nearby residue, the SUR1 mutation E128K impairs trafficking, thereby reducing surface expression and causing hyperinsulinism. To augment channel density at the plasma membrane to investigate the effect of mutating this residue on channel function, we introduced the milder mutation E126A at the matching residue of SUR2A. Mutation E126A imposed a hypersensitive Rho phenotype indicative of a functional uncoupling between TMD0 and Kir6.2. These results suggest that the TMD0-Kir6.2 interface is mobile and that the gating modes of Kir6.2 correlate with distinct positions of TMD0. They further demonstrate that the second intracellular loop of SUR, which contains the two residues studied here, is a key structural element of the TMD0-Kir6.2 interface.

Improving application QoS with residential multihoming

An appealing solution for a networked end host to circumvent last mile congestion is to connect to multiple service providers simultaneously, which is known as multihoming. The differences in peering relationships among different service providers make it possible for multihomed hosts to use significantly different routes to the same destination. Therefore, multihoming can dynamically avoid points of congestion in the network by taking advantage of the choice among different routes available at any given time. In this paper, we evaluate the potential benefits of residential multihoming for different classes of applications. For Web access applications, we show that response times and download times can be significantly reduced by multihoming, and this is achievable by employing a simple measurement-based switching algorithm. For Voice-over-IP (VoIP) applications, we show via analysis and wide area experiments that perceived voice quality, as quantified by the Mean Opinion Score (MOS) metric, can be improved with a combination of multihoming and forward error correction coding. Finally, for video streaming applications, performance improvements can be realized by splitting video sessions over multiple physical links and migrating sessions to non-congested paths. Collectively, these results suggest that multihoming can be an effective solution to provide quality of service for diverse classes of Internet applications for residential users.

Design of logical topologies: a linear formulation for wavelength-routed optical networks with no wavelength changers

We consider the problem of constructing logical topologies over a wavelength-routed optical network with no wavelength changers. We present a general linear formulation which considers routing traffic demands, and routing and assigning wavelengths to lightpaths, as a combined optimization problem. The formulation also takes into account the maximum number of hops a lightpath is permitted to take, multiple logical links in the logical topology, multiple physical links in the physical topology, and symmetry/asymmetry restrictions in designing logical topologies. The objective is to minimize congestion. We show by examples how equality and inequality logical degree constraints have a bearing on congestion. We prove that, under certain conditions, having equality degree constraints with multiple edges allowed in the design of logical topologies does not affect congestion. This helps in reducing the dimensionality of the search space and hence speeds up the search for an optimal solution of the linear formulation. We solve the linear formulation for small examples and show the tradeoff between congestion, number of wavelengths available and the maximum number of hops a lightpath is allowed to take. For large networks, we solve the linear formulation by relaxing the integer constraints. We develop topology design algorithms for large networks based on rounding the solutions obtained by solving the relaxed problem. Since the whole problem is linearizable, the solution obtained by relaxation of the integer constraints yields a lower bound on congestion. This is useful in comparing the efficiency of our heuristic algorithms. Following Bienstock and Gunluk (1995), we introduce a cutting plane which helps in obtaining better lower bounds on congestion and also enables us to reduce the previously obtained upper bounds on congestion.

An approximate solution for the resequencing problem in packet-switching networks

An approximation heuristic is proposed for solving the heterogeneous multi-server queueing problem associated with the analysis of resequencing of packets travelling over multiple physical links in a packet-switching network. Even though a method for obtaining the exact solution exists, its processing time and memory requirements vary exponentially in terms of the number of servers and render it infeasible even for moderately-sized systems. Precision of the proposed approximation which has linear time complexity is demonstrated. The approximation is recommendable in cases when system population and resequencing delays, rather than individual link utilizations, have to be calculated. >

Design and analysis of a multilink access subsystem based on the Batcher-banyan network architecture

A multilink access subsystem based on the Batcher-banyan network architecture is proposed. With this subsystem, multiple physical output links connecting a pair of switching nodes can be shared in an effective way. The subsystem is also configurational so that there is no restriction on any particular partition of physical output links. This is accomplished by executing the proposed multilink access algorithm on a modified Batcher sorter. It is shown that the required hardware can be integrated into the Batcher sorter, and the multilink access algorithm can be integrated with the contention resolution three-phase algorithm. The overhead incurred due to the running of the multilink access algorithm is calculated and the asymptotic performance analyses of the resulting single queue multilink access switch are presented. Results show that the proposed architecture has higher capacity than the unilink access counterpart, has low delay, and has low packet loss probability with small buffer size. >

Resequencing of messages in communication networks

In this paper we study a message resequencing problem in a store-and-forward computer network where messages may go out of order while traversing logical channels. The logical channels are assumed to consist of multiple physical links which may be of different capacities. A message is dispatched to the fastest available link. Resequencing methods suggested in the literature [3] (resequencing at the channel level and resequencing at the virtual circuit level) are investigated for this link selection rule. The analysis is done on a two-node network connected by multiple links. The source node together with the set of outgoing links are modeled as an M/M/m queue with servers of different rates. The resequencing delay distribution and the average resequencing delay are derived. On multihop networks, the effect of message length, link numbers, link service rates, and the resequencing methods on resequeucing delay are investigated by simulation.