研究者詳細 - 横平　徳美

論文 - 横平　徳美

分割表示 149 件中 41 - 60 件目／全件表示 >>

AS-friendly Peer Selection Algorithm for P2P Live Streaming 査読

Yukinobu Fukushima, Tokumi Yokohira

International Journal of Multimedia Technology 4 ( 2 ) 63 - 73 2014年

Decreasing of the Number of Backup Tables in Multiple Routing Table Method for Fast IP Network Recovery 査読

Daiki Imahama, Yukinobu Fukushima, Tokumi Yokohira

The 28th International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC 2013) 823 - 826 2013年

A Per-burst Traffic Distribution Method for TCP Performance Improvement in Fixed Robust Routing 査読

Yu Sezaki, Yukinobu Fukushima, Takahiro Nabeta, Tokumi Yokohira

The 28th International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC 2013) 819 - 822 2013年

A Multi-splitting Method for Light-trail Networks 査読

Yukinobu Fukushima, Tokumi Yokohira

The 28th International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC 2013) 803 - 806 2013年

A Wavelength and Converter Assignment Scheme using Converter Usage History in Wavelength-Routed Networks 査読

Yukinobu Fukushima, Takahiro Ooishi, Tokumi Yokohira

International Journal of Computer Networks & Communicationsd 5 ( 4 ) 63 - 73 2013年

Optimization of Server Locations in Server Migration Service 査読

Yukinobu Fukushima, Tutomu Murase, Tokumi Yokohira, Tatsuya Suda

The Ninth International Conference on Networking and Services (ICNS 2013) 200 - 206 2013年

A Reroute Method Using Multiple Routing Configurations for Fast IP Network Recovery 査読

Daiki Imahama, Yukinobu Fukushima, Tokumi Yokohira

2013 19TH ASIA-PACIFIC CONFERENCE ON COMMUNICATIONS (APCC): SMART COMMUNICATIONS TO ENHANCE THE QUALITY OF LIFE 433 - 438 2013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 demands on Internet reliability and availability have increased. As a routing method to recover fast from a single network component (link or node) failure, a method using multiple routing tables has been proposed. In the method, when a component failure occurs, packets which are supposed to pass through the component in no failure 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 method, there are such components that do not fail but are not used for packet forwarding in a backup table. In our proposed method, we use such components, and consequently we try to decrease the increased routing cost. Numerical examples show the effectiveness of our proposed method.

DOI： 10.1109/APCC.2013.6765984

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TCP Incast Avoidance Based on Connection Serialization in Data Center Networks 査読

Shigeyuki Osada, Kazutoshi Kajita, Yukinobu Fukushima, Tokumi Yokohira

2013 19TH ASIA-PACIFIC CONFERENCE ON COMMUNICATIONS (APCC): SMART COMMUNICATIONS TO ENHANCE THE QUALITY OF LIFE 142 - 147 2013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 distributed file systems, a well-known congestion collapse called TCP Incast occurs because many servers send data to the same client and then many packets overflow the port buffer of the client link. Incast leads to throughput degradation in the network. In this paper, we propose two methods to avoid Incast based on the fact that only one connection can almost fully use the network bandwidth because the bandwidth-delay product is not so large 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 method is a method which overlaps the slow start period of the next connection to the current established connection to improve throughput in the first method. Numerical results from extensive simulation runs show the effectiveness of our two proposed methods.

DOI： 10.1109/APCC.2013.6765931

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Improvement of a TCP Incast Avoidance Method for Data Center Networks 査読

Kazutoshi Kajita, Shigeyuki Osada, Yukinobu Fukushima, Tokumi Yokohira

2013 INTERNATIONAL CONFERENCE ON ICT CONVERGENCE (ICTC 2013): FUTURE CREATIVE CONVERGENCE TECHNOLOGIES FOR NEW ICT ECOSYSTEMS 460 - 465 2013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 distributed file systems, a well-known congestion collapse called TCP Incast occurs because many servers send data to the same client and then many packets overflow the port buffer of the client link. Incast leads to throughput degradation in the network In our previous work, we have proposed a method to avoid Incast. In the method, we limit the maximum number of simultaneously existing connections to a predetermined constant value. However, we cannot use the method when the data size is small, and because we have not investigated how to optimize the maximum value, Incast may occur if the maximum value is not appropriate. In this paper, we improve the method so that it is applicable regardless of the data size and the maximum value is optimized Numerical results show the effectiveness of our proposed method.

DOI： 10.1109/ICTC.2013.6675396

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An Architecture and a MAC Protocol for Throughput Improvement in Light Trail Networks 査読

Wenjie Chen, Yukinobu Fukushima, Tokumi Yokohira

IEICE TRANSACTIONS ON COMMUNICATIONS E95B ( 7 ) 2330 - 2343 2012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：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

Light trail architecture is attracting attention as a new optical wavelength-division multiplexing network architecture that can be built with currently available devices and can achieve bandwidth allocation with granularity finer than a wavelength. Because a light trail is a shared medium, we need a medium access control (MAC) protocol to prevent collisions. Although MAC protocols using token passing can prevent collisions, the bandwidths of links that are located upstream of the token holding node are kept idle. We first propose a dynamic light trail splitting method for increasing throughput of a light trail by using such idle bandwidths. Our method splits a trail into upstream and downstream trails at the token holding node, and independent data transmission on the two trails are permitted. As a result, we expect that the split trail architecture will achieve higher throughput than the original non-split trail architecture. The degree of performance improvement with the split trail architecture depends on how appropriately we determine the upstream and downstream token holding times of every transmission node. Thus, we formulate a problem in which we optimize the token holding times to accommodate requested traffic volume as a linear programming problem. We then derive the throughput of the split trail architecture by solving the problem using the NUOPT solver and investigate the degree of improvement over the original architecture. In addition, we evaluate the end-to-end delay of the split trail architecture by simulation. According to numerical examples, the split trail architecture achieves 1) almost the same throughput as the original one for the worst-case traffic pattern where every transmission node sends data to the terminating node of the trail only, 2) about 1.6 times higher throughput for a uniform traffic pattern where every node pair requests the same traffic volume and an extremely unbalanced traffic pattern where only a few node pairs request huge traffic volume, 3) about 1.9 time higher throughput for the split trail architecture's good-case traffic pattern where every transmission node sends data to its adjacent downstream node only, and 4) the end-to-end delay enough to satisfy any application's QoS requirement according to ITU-T Recommendation Y.1541.

DOI： 10.1587/transcom.E95.B.2330

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Throughput Improvement for TCP with a Performance Enhancing Proxy Using a UDP-Like Packet Sending Policy 査読

Hui Wang, Yuichi Nishida, Yukinobu Fukushima, Tokumi Yokohira, Zhen Wu

IEICE TRANSACTIONS ON COMMUNICATIONS E95B ( 7 ) 2344 - 2357 2012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：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG

To improve TCP throughput even if the maximum receiving window size is small, a TCP performance enhancing proxy (PEP) using a UDP-like packet sending policy with error control has been proposed. The PEP operates on a router along a TCP connection. When the PEP receives a data packet from the source host, it transmits the packet to the destination host, copies the packet into the local buffer (PEP buffer) in case the packets need to be transmitted and sends a premature ACK acknowledging receipt of the packet to the source host. In the PEP, the number of prematurely acknowledged packets in the PEP buffer is limited to a fixed threshold (watermark) value to avoid network congestion. Although the watermark value should be adjusted to changes in the network conditions, watermark adjusting algorithms have not been investigated. In this paper, we propose a watermark adjusting algorithm the goal of which is to maximize the throughput of each connection as much as possible without excessively suppressing the throughputs of the other connections. In our proposed algorithm, a newly established connection uses the initial watermark value of zero to avoid drastic network congestion and increases the value as long as its throughput increases. In addition, when a new connection is established, every already-established connection halves its watermark value to allow the newly established connection to use some portion of the bandwidth and increases again as long as its throughput increases. We compare the proposed algorithm (CW method) with other methods: the FW method that uses a fixed large watermark value and the NP method that does not use the PER Numerical results with respect to throughput and fairness showed that the CW method is generally superior to the other two methods.

DOI： 10.1587/transcom.E95.B.2344

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Destination selection algorithm in a server migration service 査読

Asato Yamanaka, Yukinobu Fukushima, Tokumi Yokohira, Tutomu Murase, Tatsuya Suda

Proceedings of the 7th International Conference on Future Internet Technologies, CFI'12 15 - 20 2012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）

Using network virtualization technologies for network applications (NW-Apps) consisting of server and clients, we can implement a server migration service where there are many server running environments (working places: WPs) inside a network and servers onWPs can migrate to otherWPs when communication QoSs in some NW-Apps fall off. Because server size is large, the traffic for server migration causes QoS degradation of its background traffic. Thus, it is important to decrease the degree (network impact) of the QoS degradation. In this paper, we propose three destination selection algorithms, MIA (Minimum Impact Algorithm), MRA (Maximum Remaining space Algorithm) and MCA (Maximum Covering Algorithm) that try to decrease the impact while increasing the number of NW-Apps' clients whose SLA (service level agreement) are satisfied. When a server migration is triggered, MIA, MRA and MCA move the server in the WP with the minimum impact, the WP with the maximum remaining space for servers and the WP with the maximum coverage, which is the number of routers under which the corresponding clients can communicate with the server while satisfying the SLA, respectively. Numerical examples show that when the number of accommodatable servers in full-cover WP (a full-cover WP is such WP that communicates with an arbitrary client while satisfying the SLA) is small or there is no full-cover WP, MIA outperforms the others, otherwise MCA outperforms the others. Copyright © 2012 by the Association for Computing Machinery, Inc.

DOI： 10.1145/2377310.2377315

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Inter-AS Traffic Volume Reduction by Localizing Delivery for P2P Live Streaming 査読

Kazuki Kobayashi, Yukinobu Fukushima, Tokumi Yokohira

2012 THIRD INTERNATIONAL CONFERENCE ON NETWORKING AND COMPUTING (ICNC 2012) 156 - 161 2012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, there is a big demand for live streaming service over the Internet. As one of the service model, peer-to-peer (P2P) live streaming has been utilized. In the system, it is important to decrease inter-AS (Autonomous System) traffic volume and content delivery delay because the larger volume leads to higher transit cost of ASes and this system treats the live contents, respectively. Therefore, as a conventional peer selection algorithm that tries to decrease them, Minimum Physical Hop (MPH) has been proposed. In MPH, to decrease inter-AS traffic volume, a newly joining peer selects a providing peer with the minimum physical hop count, which is the minimum number of ASes between the providing peer and the newly joining peer. Furthermore, to decrease content delivery delay, if there are several such candidates, it selects a providing peer with the minimum logical hop count, which is the number of Origin Streaming Servers (OSS) or peers passed from an OSS to the peer, from the candidates. However, MPH shows high inter-AS traffic volume when the number of joining peers is large. When we use MPH, candidates for providing peer with large logical hop count tend to swarm in ASes without an OSS while those with small logical hop count do in ASes with an OSS because of the peer selection policy of MPH. As the number of joining peers becomes large, the logical hop counts of the candidates for providing peer in every AS increase. As a result, in the former ASes, the logical hop counts of all the candidates for providing peer reach the upper bound frequently, and the newly joining peer cannot often find its providing peer in the AS, and consequently have to select providing peers in different ASes. In this paper, we improve MPH in order to further decrease the inter-AS traffic volume. In the improved algorithm called Improved Minimum Physical Hop (IMPH), we try to decrease the volume by distributing providing peers with one logical hop count to many ASes. As a result of the evaluation, we show that IMPH achieves to reduce the inter-AS traffic volume by at a maximum of 38% compared to MPH under uniform peer generation distributions.

DOI： 10.1109/ICNC.2012.31

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A Solution to Transmission Halting In a New Flow Control Method TCP-fox 査読

Takumi Shinkai, Wang Hui, Hiroyuki Ishihara, Yuichi Nishida, Yukinobu Fukushima, Tokumi Yokohira

18TH ASIA-PACIFIC CONFERENCE ON COMMUNICATIONS (APCC 2012): GREEN AND SMART COMMUNICATIONS FOR IT INNOVATION 806 - 811 2012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

TCP-fox is a new flow control method for TCP (Transmission Control Protocol) which allows the sender of a connection to send packets over the receive window advertised by the receiver to obtain higher throughput. However, TCP-fox has the problem that it halts sending packets when the receiver uses a receive buffer auto tuning mechanism. In this paper, we investigate the cause of the halting and present a way to avoid it.

DOI： 10.1109/APCC.2012.6388193

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Improvement of an ACK returning method of TCP proxies in network environment with wireless LANs 査読

Naohiro Honda, Wang Hui, Yuichi Nishida, Yukinobu Fukushima, Tokumi Yokohira

1st IEEE Global Conference on Consumer Electronics 2012, GCCE 2012 704 - 708 2012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）

In a network environment including a wireless LAN and a wired network, split-connection type proxies have been proposed to improve TCP (Transmission Control Protocol) throughput. A proxy is placed at the boundary between a wireless LAN and a wired network, and it splits a TCP connection which is established between a host (WSTA) in a wireless LAN and a host (STA) in a wired network into two virtual TCP connections. We have proposed a split-connection proxy called DA-Proxy, and simulation results in our previous works show that although the DA-Proxy can increase throughput of downflows (flows from STAs to WSTAs), throughput of upflows (flows from WSTAs to STAs) is not improved and is almost the same as that of upflows without the proxy. In this paper, we propose a new proxy called MDA-Proxy which tries to increase throughput of upflows by decreasing the number of ACKs in a WLAN and show its effectiveness using simulation results. © 2012 IEEE.

DOI： 10.1109/GCCE.2012.6379960

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Hybrid Fixed Robust Routing Taking Account of TCP Performance 査読

Takahiro Nabeta, Yukinobu Fukushima, Tokumi Yokohira

The 27th International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC 2012), CD-ROM (4 pages) 2012年

Optimal TCP Receive Buffer Size under Packet Loss Environment 査読

Kazutoshi Kajita, Takumi Shinkai, Naohiro Honda, Yukinobu Fukushima, Tokumi Yokohira

The 27th International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC 2012), CD-ROM (4 pages) 2012年

Multi-stage change-point detection scheme for large-scale simultaneous events 査読

Yukinobu Fukushima, Tutomu Murase, Masayoshi Kobayashi, Hiroki Fujiwara, Ryohei Fujimaki, Tokumi Yokohira

COMPUTER COMMUNICATIONS 34 ( 15 ) 1810 - 1821 2011年9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：ELSEVIER SCIENCE BV

Change-point detection schemes, which represent one type of anomaly detection schemes, are a promising approach for detecting network anomalies, such as attacks and epidemics by unknown viruses and worms. These events are detected as change-points. However, the schemes generally also detect false-positive change-points caused by other events, such as improper parameter setting of detectors. Therefore there is a requirement for a scheme that detects only true-positive change-points caused by attacks and epidemics by unknown viruses and worms. The true-positive change-points tend to occur simultaneously and intensively in very large numbers, while the false-positive change-points tend to occur independently. Therefore, we expect that the multi-stage change-point detection scheme, which performs change-point detection in a distributed manner and takes account of the correlation among multiple change-points, can exclude false-positive change-points by neglecting those that occur independently. In this paper, we propose the multi-stage change-point detection scheme and introduce a weighting function that gives smaller weight to LDs with higher false-positive rate inferred by GD in order to avoid a set of false-positive alerts generated by the low-accuracy detectors from causing high false-positive rate of the scheme. We evaluate the performance of the scheme by a simulation using the parameter values obtained in an experiment using real random scan worms. In the evaluation, we modify AAWP (Analytical Active Worm Propagation) model so that it can derive the number of infected hosts (i.e., attack hosts) more accurately by considering a failure of infection behavior by random scan worms. The simulation results show that our scheme can achieve an optimal performance (detection rate of 1.0 and false-positive rate of 0) while the stand-alone change-point detection scheme, which does not use the correlation among multiple change-points, cannot attain such optimal performance, and our scheme with alert weighting always shows better detection performance than the scheme without alert weighting. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.comcom.2011.05.001

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Performance evaluation of TCP over multiple paths in fixed robust routing 査読

Wenjie Chen, Yukinobu Fukushima, Takashi Matsumura, Yuichi Nishida, Tokumi Yokohira

2011 IEEE International Workshop Technical Committee on Communications Quality and Reliability, CQR 2011 2011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）

Fixed robust routing is a promising approach for ISP networks to accommodate variable traffic patterns with low operational complexity. The routing minimizes the maximum link load by distributing traffic of every source-destination pair to multiple paths (multipath routing). The multipath routing can result in performance degradation of TCP because of frequent out-of-order packet arrivals. In this paper, we first investigate the influences of delay differences among multiple paths and ratio of shorter paths among multiple paths on TCP performance with simulation using ns-2. The simulation results clarify that smaller delay difference and lower ratio of shorter paths among multiple paths lead to higher TCP throughput. Based on the investigation results, we next propose fixed robust routing algorithms that try to improve TCP throughput in addition to decreasing the maximum link load. The first algorithm called MDD (Minimum Delay Difference) selects a set of paths with the minimum delay differences between the shortest and the longest paths as candidate paths for every source-destination pair The second algorithm called MDD-LF (Minimum Delay Difference with Limited Fraction) bounds the fraction of traffic routed on the shortest delay path in addition to selecting the same candidate paths as MDD. Simulations using ns-2 show that, compared to a straightforward fixed robust routing that selects k-shortest hop paths as the candidate paths, MDD and MDD-LF achieve about 22% and 27% higher TCP throughput while MDD and MDD-LF produce about 1.7 and 2.3 times higher maximum link load, respectively. © 2011 IEEE.

DOI： 10.1109/CQR.2011.5996088

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Optimization of Token Holding Times in Split Light Trail Networks 査読

Wenjie Chen, Yukinobu Fukushima, Tokumi Yokohira

2011 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE (GLOBECOM 2011) 2011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

As a new optical WDM network architecture that can be built with currently available devices and can achieve bandwidth allocation with granularity finer than a wavelength, a light trail architecture attracts attention. Because a light trail is a shared medium, we need a medium access control (MAC) protocol to avoid collisions. Although MAC protocols using token passing can avoid collisions, bandwidths of links that locate upstream of the token holding node are kept idle. In this paper, we first propose a dynamic light trail splitting method in order to increase throughput of a light trail by using those idle bandwidths. Our method splits a trail into the upstream trail and the downstream trail at the token holding node and independent data transmissions on the two trails are permitted. As a result, we expect that the split trail architecture achieves higher maximum throughput than the original non-split trail architecture. The degree of throughput improvement by the split trail architecture depends on how appropriately we set upstream and downstream token holding times of every transmission node. Thus, we formulate a problem to decide the token holding times as a nonlinear programming problem, derive the maximum throughput of the split trail architecture by solving the problem using NUOPT solver, and investigate the degree of improvement compared to the original architecture. According to numerical examples, the split trail architecture achieves 1) almost the same maximum throughput as the original one for its unfavorite traffic pattern where every transmission node sends data to the terminating node of the trail only, 2) about 1.6 times as high maximum throughput for a uniform traffic pattern where every node-pair requests the same traffic volume, and 3) about 1.9 time as high maximum throughput for its favorite traffic pattern where every transmission node sends data to its adjacent downstream node only.

DOI： 10.1109/GLOCOM.2011.6133810

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