9,299 research outputs found
PABO: Mitigating Congestion via Packet Bounce in Data Center Networks
In today's data center, a diverse mix of throughput-sensitive long flows and
delay-sensitive short flows are commonly presented in shallow-buffered
switches. Long flows could potentially block the transmission of
delay-sensitive short flows, leading to degraded performance. Congestion can
also be caused by the synchronization of multiple TCP connections for short
flows, as typically seen in the partition/aggregate traffic pattern. While
multiple end-to-end transport-layer solutions have been proposed, none of them
have tackled the real challenge: reliable transmission in the network. In this
paper, we fill this gap by presenting PABO -- a novel link-layer design that
can mitigate congestion by temporarily bouncing packets to upstream switches.
PABO's design fulfills the following goals: i) providing per-flow based flow
control on the link layer, ii) handling transient congestion without the
intervention of end devices, and iii) gradually back propagating the congestion
signal to the source when the network is not capable to handle the
congestion.Experiment results show that PABO can provide prominent advantage of
mitigating transient congestions and can achieve significant gain on end-to-end
delay
Software systems for operation, control, and monitoring of the EBEX instrument
We present the hardware and software systems implementing autonomous
operation, distributed real-time monitoring, and control for the EBEX
instrument. EBEX is a NASA-funded balloon-borne microwave polarimeter designed
for a 14 day Antarctic flight that circumnavigates the pole. To meet its
science goals the EBEX instrument autonomously executes several tasks in
parallel: it collects attitude data and maintains pointing control in order to
adhere to an observing schedule; tunes and operates up to 1920 TES bolometers
and 120 SQUID amplifiers controlled by as many as 30 embedded computers;
coordinates and dispatches jobs across an onboard computer network to manage
this detector readout system; logs over 3~GiB/hour of science and housekeeping
data to an onboard disk storage array; responds to a variety of commands and
exogenous events; and downlinks multiple heterogeneous data streams
representing a selected subset of the total logged data. Most of the systems
implementing these functions have been tested during a recent engineering
flight of the payload, and have proven to meet the target requirements. The
EBEX ground segment couples uplink and downlink hardware to a client-server
software stack, enabling real-time monitoring and command responsibility to be
distributed across the public internet or other standard computer networks.
Using the emerging dirfile standard as a uniform intermediate data format, a
variety of front end programs provide access to different components and views
of the downlinked data products. This distributed architecture was demonstrated
operating across multiple widely dispersed sites prior to and during the EBEX
engineering flight.Comment: 11 pages, to appear in Proceedings of SPIE Astronomical Telescopes
and Instrumentation 2010; adjusted metadata for arXiv submissio
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Challenges to the Integration of Renewable Resources at High System Penetration
Successfully integrating renewable resources into the electric grid at penetration levels to meet a 33 percent Renewables Portfolio Standard for California presents diverse technical and organizational challenges. This report characterizes these challenges by coordinating problems in time and space, balancing electric power on a range of scales from microseconds to decades and from individual homes to hundreds of miles. Crucial research needs were identified related to grid operation, standards and procedures, system design and analysis, and incentives, and public engagement in each scale of analysis. Performing this coordination on more refined scales of time and space independent of any particular technology, is defined as a “smart grid.” “Smart” coordination of the grid should mitigate technical difficulties associated with intermittent and distributed generation, support grid stability and reliability, and maximize benefits to California ratepayers by using the most economic technologies, design and operating approaches
Video Stream Retrieval of Unseen Queries using Semantic Memory
Retrieval of live, user-broadcast video streams is an under-addressed and
increasingly relevant challenge. The on-line nature of the problem requires
temporal evaluation and the unforeseeable scope of potential queries motivates
an approach which can accommodate arbitrary search queries. To account for the
breadth of possible queries, we adopt a no-example approach to query retrieval,
which uses a query's semantic relatedness to pre-trained concept classifiers.
To adapt to shifting video content, we propose memory pooling and memory
welling methods that favor recent information over long past content. We
identify two stream retrieval tasks, instantaneous retrieval at any particular
time and continuous retrieval over a prolonged duration, and propose means for
evaluating them. Three large scale video datasets are adapted to the challenge
of stream retrieval. We report results for our search methods on the new stream
retrieval tasks, as well as demonstrate their efficacy in a traditional,
non-streaming video task.Comment: Presented at BMVC 2016, British Machine Vision Conference, 201
Limits of behavioral control by temporally extended response -reinforcer relations
Three experiments were performed to determine the extent to which the behavior of rats can be controlled by response-reinforcer relations that are extended in time. In Experiment 1, bonus pellets delivered at the end of the session were contingent upon a shift in choice responding within the session. Experiment 2 examined control of aggregated responses by a delayed consequence over a much shorter time period than an entire session. The reinforcing efficacy of bonus pellets was assessed using a chained-schedule procedure. The relation between aggregated responses and a delayed reinforcing consequence was assessed several times per session and with shorter delays than in Experiment 1. Experiment 3 used an adjusting-delay procedure to assess whether differential reinforcer magnitudes have a differential effect on choice behavior when the delay between choice and subsequent reinforcement is equal for the two alternatives. The experiment was designed to determine the longest delay at which differential reinforcement is effective. Taken together, these three experiments were designed to determine the extent to which aggregated responses may be controlled by aggregated reinforcers or a single reinforcing event, and the extent to which a single response may be reinforced by its delayed consequence. Experiment 1 failed to produce reliable control of choice responding by the post-session consequence. Experiment 2 established control of responding by the delayed reinforcer, but such control was reliable for all rats only at delays of 40 s and less. Experiment 3 was unsuccessful in establishing discriminated choice performance by the large reinforcer, even at short delays, preventing the determination of the temporal limit of control by differential reinforcer magnitude. Overall, the results of this series of experiments suggest that the operant behavior of rats can be controlled by delayed consequences, but a finite limit to such control exists. It seems that reinforcers delayed on the order of several minutes or more are unlikely to control the behavior that produces them. Thus, response-reinforcer contiguity determines whether response-reinforcer correlations can control behavior
A Study of Application-awareness in Software-defined Data Center Networks
A data center (DC) has been a fundamental infrastructure for academia and industry for many years. Applications in DC have diverse requirements on communication. There are huge demands on data center network (DCN) control frameworks (CFs) for coordinating communication traffic. Simultaneously satisfying all demands is difficult and inefficient using existing traditional network devices and protocols. Recently, the agile software-defined Networking (SDN) is introduced to DCN for speeding up the development of the DCNCF. Application-awareness preserves the application semantics including the collective goals of communications. Previous works have illustrated that application-aware DCNCFs can much more efficiently allocate network resources by explicitly considering applications needs.
A transfer application task level application-aware software-defined DCNCF (SDDCNCF) for OpenFlow software-defined DCN (SDDCN) for big data exchange is designed. The SDDCNCF achieves application-aware load balancing, short average transfer application task completion time, and high link utilization. The SDDCNCF is immediately deployable on SDDCN which consists of OpenFlow 1.3 switches. The Big Data Research Integration with Cyberinfrastructure for LSU (BIC-LSU) project adopts the SDDCNCF to construct a 40Gb/s high-speed storage area network to efficiently transfer big data for accelerating big data related researches at Louisiana State University.
On the basis of the success of BIC-LSU, a coflow level application-aware SD- DCNCF for OpenFlow-based storage area networks, MinCOF, is designed. MinCOF incorporates all desirable features of existing coflow scheduling and routing frame- works and requires minimal changes on hosts.
To avoid the architectural limitation of the OpenFlow SDN implementation, a coflow level application-aware SDDCNCF using fast packet processing library, Coflourish, is designed. Coflourish exploits congestion feedback assistances from SDN switches in the DCN to schedule coflows and can smoothly co-exist with arbitrary applications in a shared DCN. Coflourish is implemented using the fast packet processing library on an SDN switch, Open vSwitch with DPDK. Simulation and experiment results indicate that Coflourish effectively shortens average application completion time
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