掲載種別：研究論文（学術雑誌）  

Current IaaS (infrastructure as a service) cloud service may not satisfy communication QoS (quality of service) requirements of delay-sensitive network applications, if there is a significant physical distance between a server of the network application (NetApp server) at a data center and its network application clients (NetApp clients). In order to improve communication QoS of NetApp clients, we propose server migration service (SMS) in this article. SMS allows NetApp servers to migrate among different locations in the network (1) to optimally locate themselves in relation to NetApp clients and mitigate the QoS degradation caused by location-related factors (ie, propagation delays on network links) and (2) to optimally distribute traffic load over routers and processing load over (physical) computers and decrease the energy consumption. We develop a mixed-integer programming model that determines when and to which locations NetApp servers migrate to minimize the total operating cost of SMS, that is, the sum of the monetary penalty incurred due to QoS violation and energy cost incurred due to energy consumption, while preventing NetApp servers from excessively migrating and adversely impacting QoS of the non-SMS service that share the resource of the substrate network with SMS. Simulation results show that the model developed in this article achieves up to 42% lower total operating cost of SMS compared to the model that only minimizes the monetary penalty of SMS without considering the energy cost of SMS.

DOI： 10.1002/ett.4511

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記述言語：英語  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

DOI： 10.1109/ICOIN50884.2021.9333965

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その他リンク： https://dblp.uni-trier.de/db/conf/icoin/icoin2021.html#UrimotoFTMY21

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

DOI： 10.1109/ICOIN50884.2021.9333958

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その他リンク： https://dblp.uni-trier.de/db/conf/icoin/icoin2021.html#OishiTFY21

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

DOI： 10.1109/ICTC49870.2020.9289623

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その他リンク： https://dblp.uni-trier.de/db/conf/ictc/ictc2020.html#NumataITFY20

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

© 2020 ACM. Recurrent neural network method considering traffic volume, timestamp and day of the week (RNN-VTD method) is a promising network traffic prediction method because of its high prediction accuracy. The RNN-VTD method encodes timestamp and day of the week, which are categorical data, to numerical data using label encoding. The label encoding, however, gives magnitude to the encoded values, which may cause misunderstanding of recurrent neural network models, and consequently, the prediction accuracy of the RNN-VTD method may be degraded. In this paper, we investigate the effect of using one-hot encoding instead of label encoding for a feature encoding method in the RNN-VTD method. In the one-hot encoding, each input data is encoded to an k-dimensional 0 - 1 vector where k is the number of category types. Because the encoded data do not have magnitude, it is expected that the prediction accuracy of the RNN-VTD method is improved.

DOI： 10.1145/3395245.3396441

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

DOI： 10.1109/ICTC46691.2019.8939877

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その他リンク： https://dblp.uni-trier.de/db/conf/ictc/ictc2019.html#KishimotoOTFY19

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Cloud storage has become popular and is being used to hold important data. As a result, availability to become important; cloud storage providers should allow users to upload or download data even if some part of the system has failed. In this paper, we discuss distributed cloud storage that is robust against failures. In distributed cloud storage, multiple replicas of each data chunk are stored in the virtual storage at geographically different locations. Thus, even if one of the virtual storage systems becomes unavailable, users can access the data chunk from another virtual storage system. In distributed cloud storage, the placement of the virtual storage system is important; if the placement of the virtual cloud storage system means that a large number of virtual storages are possible could become unavailable from a failure, a large number of replicas of each data chunk should be prepared to maintain availability. In this paper, we propose a virtual storage placement method that assures availability with a small number of replicas. We evaluated our method by comparing it with three other methods. The evaluation shows that our method can maintain availability while requiring only with 60% of the network costs required by the compared methods.

DOI： 10.1587/transcom.2015EBP3292

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

To reduce the power consumption in data centers, the coordinated control of the air conditioner and the servers is required. It takes tens of minutes for changes of operational parameters of air conditioners including outlet air temperature and volume to be reflected in the temperature distribution in the whole data center. So, the proactive control of the air conditioners is required according to the prediction temperature distribution corresponding to the load on the servers. In this paper, the temperature distribution and the power efficiency of air conditioner were predicted by using a machine-learning technique, and also we propose a method to follow-up proactive control of the air conditioner under the predicted optimum condition. Consequently, by the follow-up proactive control of the air conditioner and the load of servers, power consumption reduction of 30% at maximum was demonstrated.

DOI： 10.1109/IC2E.2016.39

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

Some communications between devices are limited by network boundaries for ensuring security. In these cases, IEEE1888 does not provide inter-device communication. We thus propose IEEE1888 over WebSocket for communication between devices across network boundaries. In IEEE1888 over WebSocket, two devices are added to an IEEE1888 network for communication across network boundaries, so devices using traditional IEEE1888 need not to be changed. We implemented an experimental system of IEEE1888 overWebSocket. The results shows that IEEE1888 over WebSocket enables communication across network boundaries.

DOI： 10.1109/COMPSAC.2016.131

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

We propose a novel network model for real-time prediction of temperature distribution in a data center so as to allow energy-efficient task assignment and facility management. We model various physical relationships in the data center as a network, including heat movements caused by airflow and heat generation by servers. Since changes in temperature distribution depend on physical properties of the data center such as equipment locations and server types, model parameters (connection weights in the network) that characterize relationship of nodes are determined by a machine learning technique using actual data center operation data. The proposed method provides prediction results in a shorter time than traditional methods such as model based on computational fluid dynamics and potential flow model, while maintaining prediction accuracy. We evaluate the performance of the proposed model through comparison with actual data from our experimental data center. The evaluation indicates that the proposed model can predict 10-minute future temperature distributions in 60 places in 3.3 ms, with a root mean square error of 0.49 degrees.

DOI： 10.1109/CloudNet.2015.7335319

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

To decrease the power consumption of data centers, coordinated control of air conditioners and task assignment on servers is crucial. It takes tens of minutes for changes of operational parameters of air conditioners including outlet air temperature and volume to be actually reflected in the temperature distribution in the whole data center. Proactive control of the air conditioners is therefore required according to the predicted temperature distribution, which is highly dependent on the task assignment on the servers. In this paper, we apply a machine learning technique for predicting the temperature distribution in a data center. The temperature predictor employs regression models for describing the temperature distribution as it is predicted to be several minutes in the future, with the model parameters trained using operational data monitored at the target data center. We evaluated the performance of the temperature predictor for an experimental data center, in terms of the accuracy of the regression models and the calculation times for training and prediction. The temperature distribution was predicted with an accuracy of 0.095 degrees C. The calculation times for training and prediction were around 1,000 seconds and 10 seconds, respectively. Furthermore, the power consumption of air conditioners was decreased by roughly 30% through proactive control based on the predicting temperature distribution.

DOI： 10.1109/CloudCom.2015.49

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

The concept of a Home Energy Management System (HEMS) as a power-saving technology for home appliances has received much attention. Most of current HEMSs based on the Smart Energy Profile (SEP), KNX, or ECHONET standards are implemented as closed systems within a Home Area Network (HAN); therefore, cost is a serious problem in the large-scale deployment of HEMSs. One possible way to reduce the overhead is to implement a HEMS as a cloud-based Application Service Provider (ASP) service. In such setup, a HEMS server is located in the cloud, and it monitors and controls home appliance devices over the Internet. We propose here a novel HEMS architecture using a cloud-based ASP service. We describe an overall architecture and some potential interactive Web communication technologies that realize a HEMS over the cloudbased ASP services. We also present a mathematical analysis and experimental results for estimating protocol overheads and server loads. These show that the WebSocket protocol is the most suitable protocol, allowing accommodation of twice as many households as other protocols. Finally, we describe our prototype implementation of the proposed architecture with the WebSocket protocol.

DOI： 10.1109/SmartGridComm.2015.7436399

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OPTICAL SOC AMER  

Energy consumption by data centers has become a serious problem, and measures for its reduction should be developed. Such measures should address not only the energy consumption of the servers but also that of the network itself, because the latter is responsible for a substantial portion of the total energy consumption. One approach to reducing the energy consumption of the network within a data center is to use optical circuit switches (OCSs) at the core of the data center, where electronic switches are connected to the OCSs. In such a network, a virtual network can be configured by setting the OCSs to connect different ports of the electronic packet switches. Thus, the energy consumption of the network can be reduced by configuring the virtual network to minimize the number of ports required by the electronic packet switches and powering down any unused ports. In this paper, we propose a method called virtual network reconfiguration for data center networks (VNR-DCN) that immediately reconfigures the virtual network so as to reduce the energy consumption under the constraints on the bandwidth and delay between servers in data center networks based on optical communication paths. In VNR-DCN, we configure the virtual network to satisfy the requirements by setting the parameters of the topology, called generalized flattened butterfly, instead of solving an optimization problem. In the evaluation, we show that a virtual network configured by VNR-DCN requires a small number of active ports. In addition, we show the impact of virtual network configuration on energy consumption.

DOI： 10.1364/JOCN.6.000925

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OPTICAL SOC AMER  

Traffic information is required to perform opticallayer traffic engineering (TE). However, as the number of nodes in optical networks increases, the overhead for collecting the traffic volume information becomes large. In this paper, we develop a method that reduces the overhead for collecting traffic volume information by selecting a subset of nodes and by only collecting the traffic volume information from the selected nodes. Then, we estimate the traffic volume using the information gathered from the selected nodes. According to the simulation results, we clarify that our method can accurately identify the congested links in real ISP topologies, where the number of traffic demands passing through some links is large; however, the estimation errors of our method become large when the number of traffic demands passing each link is small. Furthermore, optical-layer TE can sufficiently mitigate congestion by using the traffic volume estimated by our method from the information on 50% of all nodes in the case of the Japan topology and 30% of all nodes in the case of the AT&T topology.

DOI： 10.1364/JOCN.4.000038

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

A data center network should provide communication with sufficiently large bandwidth and small delay between all servers. On the other hand, energy consumption of the data center network should be minimized. To satisfy all of the above requirements, in this paper, we introduce the virtual network configured over the data center network constructed of the optical cross connects (OXCs) and the electronic switches. We design the virtual network topology (VNT) so as to achieve sufficiently large bandwidth and small delay with small energy consumption. To calculate the suitable VNT in a short period, we propose the topology called Generalized Flattened Butterfly and a method to set the parameters so as to suit the current condition. In our evaluation, we clarify that our method achieves the sufficient bandwidth and the target maximum number of hops between top-of rack(ToR) switches with small energy consumption. © 2012 IEEE.

DOI： 10.1109/ICCS.2012.6406106

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IARIA XPS PRESS  

Traffic information is required to perform traffic engineering. However, as the network that require traffic engineering becomes large, the overhead to collect the traffic amount information required for traffic engineering becomes large. In this paper, we propose a method to reduce the overhead to collect the traffic amount information. In our method, we select a subset of nodes and collect the traffic amount information only from the selected nodes. Then, we estimate the traffic amount on each link by using the information collected from the selected nodes. According to simulation results, our method can estimate the traffic amount on each link required for traffic engineering accurately by monitoring 30% of all nodes.

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担当区分：筆頭著者   記述言語：日本語  

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記述言語：日本語  

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記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

本報告では、データセンタの消費電力を最小にするタスク配置及び空調機設定の導出を目的とし、実時間でデータセンタ内の温度分布を予測することができるネットワークモデルを提案する。提案するモデルにおいては、データセンタ内に存在する気流や浮力による空気の循環に伴う熱の移動や、ラックに設置されたサーバの位置関係などの様々な物理的関係をネットワークとしてモデル化し、データセンタの過去の稼働データを用いて、モデルのパラメータを機械学習によって決定する。実稼働している約400台のサーバから構成されるデータセンタの稼働データを用いて、提案モデルによる温度分布の予測を行った結果、データセンタ内の60箇所の10分後の温度予測に必要な時間は3.6ms程度であり、従来のモデルと比較して非常に小さいことがわかった。また、予測結果の二乗平均平方根誤差は、最大でも0.74℃に抑えられることを明らかにした。

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