Hitachi Yokohama Research Laboratory

Hitachi, Japan

Hitachi Yokohama Research Laboratory

Hitachi, Japan
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Yi J.,Ecole Polytechnique - Palaiseau | Clausen T.,Ecole Polytechnique - Palaiseau | Igarashi Y.,Hitachi Yokohama Research Laboratory
2013 IEEE Conference on Wireless Sensor, ICWISE 2013 | Year: 2013

Routing protocol is a critical component of Low-power and Lossy Networks for Smart Grid. The protocols are used for data forwarding, which includes data acquisition, information dissemination, etc. This paper evaluates two main routing protocols used for Low-power and Lossy Networks: RPL and LOADng, to understand their strengths and limitations. Observations are provided based on analysis of specification and experimental experience, regarding the protocol's routing overhead, traffic pattern, resource requirement, fragmentation, etc. Simulations are further launched to study the performance in different traffic patterns, which include sensor-to-sensor traffic, sensor-to-root traffic and root-to-sensor bidirectional traffic. By evaluating those protocols, the readers could have better understanding of the protocol applicability, and choose the appropriate protocol for desired applications. © 2013 IEEE.


Himura Y.,Hitachi Yokohama Research Laboratory | Yasuda Y.,Hitachi Yokohama Research Laboratory
Proceedings of the 2013 IFIP/IEEE International Symposium on Integrated Network Management, IM 2013 | Year: 2013

A recent fashion to reduce the device cost of datacenter networks is to leverage multi-tenancy, with which multiple virtual networks of different customers (tenants) are consolidated over a single physical infrastructure. The use of multi-tenancy, however, poses significant operational cost due to the complicated device configuration and the rise in risks of misconfigurations in such shared environment; Hence deploying a tenant requires network engineers to pay careful attention to validating the correctness of corresponding device configuration commands before actual deployment. In this work, we present a methodology that statically validates network device configurations before deployment by predicting a posteriori network states after execution of those commands. We mainly make use of graph-based techniques to achieve both (a) extensibility to deal with various types of network devices in datacenters (provided from abstracting configurations as graphs), as well as (b) interpretability of the validation results (provided from visualization-a key benefit from graphs). The evaluation with a dataset synthesized from a set of actual configuration files results in 68% reduction of the time to validate them on average. © 2013 IFIP.


Paoletti U.,Hitachi Yokohama Research Laboratory | Suga T.,Hitachi Yokohama Research Laboratory
IEEE International Symposium on Electromagnetic Compatibility | Year: 2012

A new concept for an LSI power supply noise model above 1 GHz is introduced, and a measurement method for the power supply noise based on a new equipment, the printed reverberation board, is presented, which we believe is able to provide the proposed LSI model. A new statistical model for characterizing the printed reverberation board is presented and confirmed by measurement results. © 2012 IEEE.


Mikami S.,Hitachi Yokohama Research Laboratory | Yoshida H.,Hitachi Yokohama Research Laboratory | Watanabe D.,Hitachi Yokohama Research Laboratory | Sakiyama K.,University of Electro - Communications
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences | Year: 2013

Enocoro-128v2 is a lightweight stream cipher submitted to Cryptography Research and Evaluation Committees (CRYPTREC). In this paper, we first describe a side channel attack on Enocoro-128v2. We show that all secret key bytes of Enocoro-128v2 can be recovered by correlation power analysis, and it is shown by an experiment that around 6000 traces are needed to recover the secret key on SASEBO-GII (Side-channel Attack Standard Evaluation Board). We second propose a countermeasure with threshold implementation technique, which allows Enocoro-128v2 to be resistant against correlation power analysis as long as less than 105 traces are used. Copyright © 2013 The Institute of Electronics, Information and Communication Engineers.


Himura Y.,Hitachi Yokohama Research Laboratory | Yasuda Y.,Hitachi Yokohama Research Laboratory
Computer Communication Review | Year: 2012

Multi-tenant datacenter networking, with which multiple customer (tenant) networks are virtualized over a single shared physical infrastructure, is cost-effective but poses sig- nificant costs on manual configuration. Such tasks would be alleviated with configuration templates, whereas a crucial difficulty stems from creating appropriate (i.e., reusable) ones. In this work, we propose a graph-based method of mining configurations of existing tenants to extract their re- current patterns that would be used as reusable templates for upcoming tenants. The effectiveness of the proposed method is demonstrated with actual configuration files ob- tained from a business datacenter network.


Chishiro E.,Hitachi Yokohama Research Laboratory | Miyata Y.,Hitachi Yokohama Research Laboratory | Yokoi K.,Hitachi Yokohama Research Laboratory | Nishiyama H.,Hitachi Yokohama Research Laboratory
Computer Software | Year: 2013

Currently, most of RDF stores adopt a materialization approach to the search with RDFS inference. While on-demand approach based on backward reasoning has several desirable properties such as small data size, short load time, and flexibility, it is not popular since its performance is rather low in particular on large RDF graphs. To address this problem, we propose an optimization method based on query transformation. As major RDFS inference rules are recursive, we could not apply naive unfolding technique. The main idea is to make a contracted graph, which is equivalent with respect to RDFS inference but compact, and exploit the result of search with inference on it. Preliminary experimental results on standard LUBM benchmark are encouraging. For some patterns, we confirmed two order of magnitude speedup.


Chishiro E.,Hitachi Yokohama Research Laboratory | Miyata Y.,Hitachi Yokohama Research Laboratory | Yokoi K.,Hitachi Yokohama Research Laboratory | Nishiyama H.,Hitachi Yokohama Research Laboratory
Computer Software | Year: 2013

Distributed SPARQL query processing is considered as a desirable solution to improve the query performance for large RDF graphs. Most previous works are based on data or query decomposition, which often results in poor scalability due to communication overheads between servers. We propose a new approach to distributed SPARQL processing based on range partitioning which needs just a single communication cycle. Preliminary experimental results for LUBM show almost linear speedups for most queries.

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