研究者詳細 - 横平　徳美

Candidate Path Selection Method for TCP Performance Improvement in Fixed Robust Routing 査読

Yukinobu Fukushima, Takashi Matsumura, Kazutaka Urushibara, Tokumi Yokohira

IEIE Transactions on Smart Processing & Computing 5 ( 6 ) 445 - 453 2016年

Modification of an Energy-Efficient Virtual Network Mapping Method for a Load-Dependent Power Consumption Model 査読

Shigeyuki Osada, Ryo Miyayama, Yukinobu Fukushima, Tokumi Yokohira

WSEAS Transactions on Communications 15 240 - 250 2016年

TCP Incast avoidance based on connection serialization in data center networks 査読

Shigeyuki Osada, Ryo Miyayama, Yukinobu Fukushima, Tokumi Yokohira

International Journal of Computer Networks and Communications 8 ( 4 ) 83 - 102 2016年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Academy and Industry Research Collaboration Center (AIRCC)

In distributed file systems, a well-known congestion collapse called TCP incast (Incast briefly) occurs because many servers almost simultaneously send data to the same client and then many packets overflow the port buffer of the link connecting to the client. Incast leads to throughput degradation in the network. In this paper, we propose three methods to avoid Incast based on the fact that the bandwidth-delay product is small in current data center networks. The first method is a method which completely serializes connection establishments. By the serialization, the number of packets in the port buffer becomes very small, which leads to Incast avoidance. The second and third methods are methods which overlap the slow start period of the next connection with the current established connection to improve throughput in the first method. Numerical results from extensive simulation runs show the effectiveness of our three proposed methods.

DOI： 10.5121/ijcnc.2016.8406

Prototype Development of a Virtual Network Embedding System Using OpenStack 査読

Itsuho Goda, Kohei Sato, Yukinobu Fukushima, Heung-Gyoon Ryu, Tokumi Yokohira

The 31st International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC 2016) 21 - 24 2016年

Nonlinearity Sensitivity of FBMC and UFMC Modulation System for the 5G Mobile System 査読

Changyoung An, Heung-Gyoon Ryu, Yukinobu Fukushima, Tokumi Yokohira

The 31st International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC 2016) 1 - 4 2016年

Performance improvement of an AS-friendly peer selection algorithm for P2P live streaming 査読

Yukinobu Fukushima, Kazuki Kobayashi, Tokumi Yokohira

International Journal of Computer Networks and Communications 8 ( 1 ) 35 - 46 2016年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Academy and Industry Research Collaboration Center (AIRCC)

Minimum Physical Hop (MPH) has been proposed as a peer selection algorithm for decreasing inter-AS (Autonomous System) traffic volume in P2P live streaming. In MPH, a newly joining peer selects a peer whose physical hop count (i.e., the number of ASes traversed on the content delivery path) from it is the minimum as its providing peer. However, MPH shows high inter-AS traffic volume when the number of joining peers is large. In this paper, we propose IMPH that tries to further decrease the inter-AS traffic volume by distributing peers with one logical hop count (i.e., the number of peers or origin streaming servers (OSSes) traversed on the content delivery path from an OSS to the peer) to many ASes and encouraging the following peers to find their providing peers within the same AS. Numerical examples show that IMPH achieves at the maximum of 64% lower inter-AS traffic volume than MPH.

DOI： 10.5121/ijcnc.2016.8103

Load Modulation Based MIMO Communication for the Low Complexity and Low Power Consumption 査読

Changyoung An, Heung-Gyoon Ryu, Seung Hwan Lee, Masahiro Umehira, Tokumi Yokohira

2016 IEEE INTERNATIONAL CONFERENCE ON CONSUMER ELECTRONICS (ICCE) 558 - 561 2016年

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

In this paper, we design LM-MIMO system using high-order m-PSK modulation and evaluate performance of the system. As simulation results, we can confirm that LM-MIMO system with high-order m-PSK modulation has a similar performance to conventional MIMO system with a number of RF chains.

DOI： 10.1109/ICCE.2016.7430711

A trail multi-splitting method for throughput improvement in light trail networks 査読

Yukinobu Fukushima, Wenjie Chen, Tokumi Yokohira

PHOTONIC NETWORK COMMUNICATIONS 30 ( 2 ) 178 - 189 2015年10月

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

Light trail networks have been proposed as an extension of lightpath networks in order to enable sub-wavelength bandwidth allocation in WDM networks. The networks need a medium access control (MAC) method to avoid collisions of data transmissions. We have proposed a MAC method which adopts a token-passing mechanism. The method splits one trail into two trails: one upstream trail and one downstream trail and permits independent data transmissions on the trails. However, the method leaves bandwidths of links upstream from the token-holding node idle because the method only splits the original trail into two trails and leaves the upstream trail unsplit. In this paper, we propose a novel token-passing MAC method for further improving trail throughputs. Our proposed method recursively splits the upstream trail, and consequently the original trail can be split into more than two trails. In the proposed method, an appropriate setting of upstream/downstream token-holding times of all nodes is a key factor to successfully accommodate an input traffic. Therefore, we tackle a problem (called a token-holding time decision problem) where we optimize token-holding times of all nodes so that input traffic is successfully accommodated. We formulate the problem as a linear programming model. Numerical examples on maximum effective throughput show that the proposed method is more superior as the ratio of short-hop traffic is higher in input traffic patterns.

DOI： 10.1007/s11107-015-0509-z

Strict application execution control with hierarchical group management using digital certificates on educational windows PCs 査読

Daisuke Okamoto, Keita Kawano, Nariyoshi Yamai, Tokumi Yokohira

Journal of Information Processing 23 ( 4 ) 449 - 457 2015年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Information Processing Society of Japan

We have developed a system (traditional system) to flexibly provide the requested applications environment on educational Windows PCs. The traditional system dynamically controls the execution of applications installed on each educational PC depending on the rules defined by teachers as well as by administrators. The traditional system, however, has a low tolerance for malicious attacks. If the execution file of a certain application is falsified, the corresponding rules already applied become invalid. In addition, though the traditional system has a function to define groups of controlled applications, it does not support hierarchical groups. This reduces the usability of the traditional system. In order to address these issues, this paper proposes a control method of application execution using digital certificates. The proposed method has a high tolerance for the falsification of execution files by controlling their executions based on the reliability of the corresponding digital certificates. It also improves its usability by introducing hierarchical group management utilizing hierarchical structure for digital certificates.

DOI： 10.2197/ipsjjip.23.449

Performance Evaluation of an Energy Efficient Virtual Network Mapping Method-In the case of load-dependent power consumption model- 査読

Yuta Hoshino, Yukinobu Fukushima, Tutomu Murase, Tokumi Yokohira, Tatsuya Suda

The International Conference on Electronics and Software Science 2015 (ICESS 2015) 134 - 144 2015年

An On-line Algorithm to Determine the Location of the Server in a Server Migration Service 査読

Yuta Hoshino, Yukinobu Fukushima, Tutomu Murase, Tokumi Yokohira, Tatsuya Suda

2015 12TH ANNUAL IEEE CONSUMER COMMUNICATIONS AND NETWORKING CONFERENCE 740 - 745 2015年

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

In IaaS cloud services, QoS of network applications (NW-Apps) may degrade due to location factors such as significant distance between a server-side application (server) of a NW-App at a data center and a client-side application (client) of the NW-App at a client terminal. In order to shorten the distance and to improve the QoS, server migration services (SMSes) have been proposed. In SMSes, servers may migrate between different computers (called work places, WPs) on a network to prevent QoS degradation caused by the changes of client locations. Although server migrations can improve QoS of NW-Apps, they also generate a huge amount of traffic (server migration traffic) in the network. This paper focuses on a server location decision problem where the location of a server is decided in an on-line manner so that QoS of a NW-App is improved under the constraint that the server migration traffic has to be suppressed below an acceptable level. For the problem, we propose a practical on-line algorithm. The key idea behind the proposed algorithm is that the location of the server is decided with consideration of the QoS degradation in the future. The algorithm defines the averagely good location for the server where the QoS is expected to be relatively good for various client locations. Then, it keeps the range of the server's migration within the returnable range where the server can soon come back to the averagely good location. As a result, the QoS can be always kept as good as the one under the averagely good location. Simulation results show that the proposed algorithm improves QoS of the NW-App by up to 30% compared to a greedy algorithm.

DOI： 10.1109/CCNC.2015.7158070

Throughput Improvement of TCP Proxies in Network Environment with Wireless LANs 査読

Wang Hui, Yukinobu Fukushima, Tokumi Yokohira

2014 IEEE REGION 10 SYMPOSIUM 82 - 87 2014年

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

Split-connection type proxies have been proposed to improve TCP (Transmission Control Protocol) throughput in network environment with wireless LANs. A proxy is placed at the boundary of a wireless LAN (WLAN) and a wired network and it splits a TCP connection into two virtual TCP connections. We proposed a split-connection type proxy called MDA-Proxy (Modified Decreasing-ACK Proxy), which increases throughput of upflows (flows from wireless hosts to wired hosts) by decreasing the number of ACKs in a WLAN. MDA-Proxy uses two parameters, ack_stock and delay_timer, for each connection. The former controls the number of ACKs sent to a WLAN and the latter is used to recover from losses and delays of ACKs in a wired network. However, it is assumed that MDA-Proxy uses fixed values of the two parameters and their automatic tuning in response to network situation remains to be future work. In this paper, we propose a new type of proxy called ASA-Proxy (Ack_Stock Autotunning Proxy), which automatically tunes the two parameters in MDA-Proxy. Ack_stock is tuned comparing throughputs before and after its changing so that throughput of the connection becomes large, and delay_timer is replaced by the normal TCP retransmission timer because it is better than a fixed value of delay_timer for the inference of losses and delays of ACKs in a wired network. Extensive simulation runs show that ASA-Proxy is superior to MDA-Proxy.

A Reroute Method to Recover Fast from Network Failure 査読

Yasuhiro Harada, Wang Hui, Yukinobu Fukushima, Tokumi Yokohira

2014 INTERNATIONAL CONFERENCE ON INFORMATION AND COMMUNICATION TECHNOLOGY CONVERGENCE (ICTC) 903 - 908 2014年

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 demand for high Internet availability has increased. As routing methods to recover fast from a single network component (link or node) failure, methods using multiple routing tables have been proposed. In the methods, when a component failure occurs, packets which are supposed to pass through the component in the failure-free state are rerouted using a routing table (backup table) which does not use the component for packet forwarding. Thus, it is important to decrease the increased routing cost (for example, the number of increased hops of rerouted packets if every link cost is one) due to the reroute as much as possible. In this paper, we propose a new routing method to decrease the increased routing cost. In the conventional methods, there are many components that do not fail but are not used for packet forwarding in a backup table. In our proposed method, we use such components as much as possible, and consequently we try to decrease the increased routing cost. Numerical examples show the effectiveness of our proposed method.

DOI： 10.1109/ICTC.2014.6983329

Optimization of Maximum Timeout Value in TCP with a Fine-grained Timer for Data Center Networks 査読

Ryo Miyayama, Shigeyuki Osada, Yukinobu Fukushima, Tokumi Yokohira

2014 INTERNATIONAL CONFERENCE ON INFORMATION AND COMMUNICATION TECHNOLOGY CONVERGENCE (ICTC) 433 - 437 2014年

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

When the standard TCP implementation is used in distributed. le systems in data center, a well-known throughput degradation called TCP Incast occurs. In order to avoid TCP Incast, a TCP implementation using a specialized. fine-grained timer is proposed. However, the throughput still decreases in the implementation when the number of servers in distributed. le systems is large. In this paper, we clarify that the cause of the decreasing is that maximum timeout value is too large and optimize the value.

DOI： 10.1109/ICTC.2014.6983174

Performance Improvement of SCTP Communication Using Selective Bicasting on Lossy Multihoming Environment 査読

Koki Okamoto, Nariyoshi Yamai, Kiyohiko Okayama, Keita Kawano, Motonori Nakamura, Tokumi Yokohira

2014 IEEE 38TH ANNUAL INTERNATIONAL COMPUTERS, SOFTWARE AND APPLICATIONS CONFERENCE (COMPSAC) 551 - 557 2014年

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

In recent years, with proliferation of smart phones and tablet PCs, speedup of wireless LAN communication is required for dealing with increase of traffic in wireless networks. However, transmission speed through a wireless network often slows down in comparison with that through a wired network since packets of wireless networks frequently drop due to the influence of surrounding environment such as electromagnetic noise. In this paper, we propose a method to mitigate the impacts caused by packet loss by virtue of SCTP bicasting in lossy multihoming environment with two or more wireless networks. This method bicasts not all packets but only important packets concerning retransmission for efficiency since bicasting all packets would cause congestion. We also implemented a prototype system based on the proposed method. According to the result of performance evaluation experiment, we confirmed the effectiveness of the proposed method by the fact that the prototype system performed faster transmission than normal SCTP transmission even in high packet loss rate environment.

DOI： 10.1109/COMPSAC.2014.78