It is necessary for onboard time management that Marine clock is adjusted to UTC at all times and various equipments are corrected to local time when standard meridian is changed. But these affairs are inconvenience to mariners, because each equipment is practically set by hand. The authors designed and tested the marine master clock with PPS (Pulse Per Second) signal and the Local Time Information (LTI) software on Windows OS. The PPS signal is outputted by hi-precision control clock, such as GPS, Radio controlled clock etc. The marine master clock is available to drive some ordinary marine slave clocks. The LTI software consist a master and many clients, use some transfer mode TCP and UDP (also broadcast mode). The results are as follows. 1) Proposed marine clock synchronized to UTC automatically, and the slave clocks are derived certainly. The synchronous precision is 13ms in standard deviation. 2) Local time of navigational GPS is set all computers by the Auto-time correction program via shipboard LAN.

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The high-availability seamless redundancy (HSR) protocol is a representative protocol that fulfills the reliability requirements of the IEC61850-based substation automation system (SAS). However, it has the drawback of creating unnecessary traffic in a network. To solve this problem, a dual virtual path (DVP) algorithm based on HSR was recently presented. Although this algorithm dramatically reduces network traffic, it does not consider the substation timing requirements of messages in an SAS. To reduce unnecessary network traffic in an HSR ring network, we introduced a novel packet transmission (NPT) algorithm in a previous work that considers IEC61850 message types. To further reduce unnecessary network traffic, we propose an extended dual virtual paths (EDVP) algorithm in this paper that considers the timing requirements of IEC61850 message types. We also include sending delay (SD), delay queue (DQ), and traffic flow latency (TFL) features in our proposal. The source node sends data frames without SDs on the primary paths, and it transmits the duplicate data frames with SDs on the secondary paths. Since the EDVP algorithm discards all of the delayed data frames in DQs when there is no link or node failure, unnecessary network traffic can be reduced. We demonstrate the principle of the EDVP algorithm and its performance in terms of network traffic compared to the standard HSR, NPT, and DVP algorithm using the OPNET network simulator. Throughout the simulation results, the EDVP algorithm shows better traffic performance than the other algorithms, while guaranteeing the timing requirements of IEC61850 message types. Most importantly, when the source node transmits heavy data traffic, the EDVP algorithm shows greater than 80% and 40% network traffic reduction compared to the HSR and DVP approaches, respectively.

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We suggest a gigabit ethernet (GbE) based time transfer technique. In this technique, timing signals used for clock error measurements are inserted into inter-frame gaps and transmitted. We developed the GbE based time transfer system and evaluated the phase stability and precision.

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We propose a scalable parallel interface that provides an ideal aggregated bandwidth link for an application. The scalable parallel interface uses time information to align packets and allows dynamic lane and/or path change, a large difference in transmission delays among lanes, and so on. The basic performance of the scalable parallel interface in 10Gb/s × 2 lanes is verified using an estimation board that is newly developed to evaluate the basic functions used in a Terabit LAN. The evaluation shows that the scalable parallel interface achieves a very low delay variation that is almost the same as that under back-to-back conditions. The difference in the delay variation between the scalable parallel interface and the back-to-back condition is approximately 10ns when the transmission delay time varies from 10µs to 1s.

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This paper proposes a system called Neary that detects conversational fields based on similarity of auditory situation among users. The similarity of auditory situation between each pair of the users is measured by the similarity of frequency property of sound captured by head-worn microphones of the individual users. Neary is implemented with a simple algorithm and runs on portable PCs. Experimental result shows Neary can successfully distinguish groups of conversations and track dynamic changes of them. This paper also presents two examples of Neary deployment to detect user contexts during experience sharing in touring at the zoo and attending an academic conference.

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Domain Name System (DNS) is a major target for the network security attacks due to the weak authentication. A security extension DNSSEC has been proposed to introduce the public-key authentication, but it is still on the deployment phase. DNSSEC assumes IP fragmentation allowance for exchange of its messages over UDP large payloads. IP fragments are often blocked on network packet filters for administrative reasons, and the blockage may prevent fast exchange of DNSSEC messages. In this paper, we propose a scheme to detect the UDP large-payload transfer capability between two DNSSEC hosts. The proposed detection scheme does not require new protocol elements of DNS and DNSSEC, so it is applicable by solely modifying the application software and configuration. The scheme allows faster capability detection to probe the end-to-end communication capability between two DNS hosts by transferring a large UDP DNS message. The DNS software can choose the maximum trans-mission unit (MTU) on the application level using the probed detection results. Implementation test results show that the proposed scheme shortens the detection and transition time on fragment-blocked transports.

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本稿では、通信プロトコルのための仕様記述言語Preccsとその処理系について説明する。通信プロトコルは主に(1)メッセージの形式と(2)メッセージ送受信の手順から構成されている。Preccsでは、(1)は拡張した正規表現を用い、(2)はCCSに代表されるプロセス代数にもとづいて記述を行う。これによって複雑な構造を持ったメッセージを簡単に表現し、プロトコルの状態遷移や通信シーケンスを簡便に記述できるようになる。さらにPreccsコンパイラを用いて通信プロトコルの仕様記述からプログラムを自動生成することによって、信頼性の高い通信プログラムを短期間で開発することが可能となる。

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近年，インターネットの普及と利用の高度化にともなって，通信プロトコルを実装する機会が多くなってきた．通信プロトコルは主として(1)メッセージの形式と，(2)メッセージ送受信の手順から規定されるが，通信プロトコルを実装するプログラマは，これに応じて，受信メッセージの解析や送信メッセージの組み立て，タイムアウトや非同期入出力といった処理を書く必要がある．これらはある程度，定型的な処理ではあるが，比較的煩雑なコーディングを必要とするため，結果としてプログラムの保守性を低下させたり，バグの原因となりやすい．本稿では，通信プロトコルの記述から自動的にプロトコル処理コードを生成するPreccsコンパイラについて説明する．Preccsではメッセージの形式を正規表現を独自に拡張した記法によって，また，メッセージの送受信手順はプロセス計算に基づいた記法によって記述を行う．Preccsコンパイラはこれらの記述からプロトコルの処理を行うCのコードを自動的に生成する．これによってプログラマは煩雑なコーディングから解放され，信頼性や保守性に優れた通信プログラムを短期間で開発することが可能となる．

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