A MAC-address Relaying NAT Router for Host Identification from Outside of Internal Network

IPv4アドレスの枯渇問題の軽減策の1つとして，NAT（Network Address Translation）がある．NATは複数の内部ホストが1つのグローバルIPアドレスを共用できるため，必要なグローバルIPアドレスの数を節約できる．しかし，外部ネットワーク側では個々の内部ホストを識別できないため，たとえば外部ネットワーク側でアクセス制御を行うと，1台の内部ホストが外部ネットワークに対するアクセス許可を受けただけで他の内部ホストまで外部ネットワークにアクセス可能な状態になるなどの問題が生じる．そこで，本論文ではデータリンク層での送信元識別子である送信元MACアドレスが基本的にはレイヤ2機器のMACアドレス学習機能にしか使われていない点に着目し，内部ホストから送信されたフレームに含まれる送信元MACアドレスをそのまま外部ネットワーク側に中継する機能を持つNATルータを提案する．本提案に基づいて試作したNATルータを評価した結果，MACアドレスに基づいて内部ホストを個別にアクセス制御でき，また十分なスループットが得られることを確認した．As an alleviation method against IPv4 address exhaustion problem, NAT (Network Address Translation) has been commonly used. Since NAT allows many internal hosts to share one single global IP address, it can save the number of required global IP addresses. However, with NAT, each internal host cannot be identified from the external network. Consequently, if access control system on external network would permit network access from one internal host, it automatically would permit all network access from any other internal hosts as well, for example. In this paper, we propose a NAT router with MAC address relaying function that copies the source MAC address of receiving frames sent by internal hosts into frames sent to the external network since source MAC addresses, which are the sender identifiers in data link layer, are basically unused except for MAC address learning function of layer 2 switches. According to the results of experiments, we confirmed that the prototype NAT router with MAC address relaying function allows access to external networks by internal hosts to be controlled individually based on MAC address and obtains high throughput as well

A protection method against massive error mails caused by sender spoofed spam mails

Wide spread of spam mails is one of the most serious problems on e-mail environment. Particularly, spam mails with a spoofed sender address should not be left alone, since they make the mail server corresponding to the spoofed address be overloaded with massive error mails generated by the spam mails, and since they waste a lot of network and computer resources. In this paper, we propose a protection method of the mail server against such massive error mails. This method introduces an additional mail server that mainly deals with the error mails in order to reduce the load of the original mail server. This method also provide a function that refuses error mails to these two mail servers to save the network and computer resources

Toward the Cross-Institutional Data Integration From Shibboleth Federated LMS

Through this study, we aim to examine a method for data integration in shared Learning Management System (LMS) in authentication federation. We proposed a method of transmitting ePTID and learning data with user’s consent as a method for data integration across institutions. The method is compared with the other existing methods to realize the shared LMS. We discuss the suitable method for next version of GakuNinMoodle and conclude that our requirements are not fully satisfied by a single method

Alternative mRNA Splicing in Three Venom Families Underlying a Possible Production of Divergent Venom Proteins of the Habu Snake, Protobothrops flavoviridis

Snake venoms are complex mixtures of toxic proteins encoded by various gene families that function synergistically to incapacitate prey. A huge repertoire of snake venom genes and proteins have been reported, and alternative splicing is suggested to be involved in the production of divergent gene transcripts. However, a genome-wide survey of the transcript repertoire and the extent of alternative splicing still remains to be determined. In this study, the comprehensive analysis of transcriptomes in the venom gland was achieved by using PacBio sequencing. Extensive alternative splicing was observed in three venom protein gene families, metalloproteinase (MP), serine protease (SP), and vascular endothelial growth factors (VEGF). Eleven MP and SP genes and a VEGF gene are expressed as a total of 81, 61, and 8 transcript variants, respectively. In the MP gene family, individual genes are transcribed into different classes of MPs by alternative splicing. We also observed trans-splicing among the clustered SP genes. No other venom genes as well as non-venom counterpart genes exhibited alternative splicing. Our results thus indicate a potential contribution of mRNA alternative and trans-splicing in the production of highly variable transcripts of venom genes in the habu snake

A pH sensor based on electric properties of nanotubes on a glass substrate

We fabricated a pH-sensitive device on a glass substrate based on properties of carbon nanotubes. Nanotubes were immobilized specifically on chemically modified areas on a substrate followed by deposition of metallic source and drain electrodes on the area. Some nanotubes connected the source and drain electrodes. A top gate electrode was fabricated on an insulating layer of silane coupling agent on the nanotube. The device showed properties of ann-type field effect transistor when a potential was applied to the nanotube from the top gate electrode. Before fabrication of the insulating layer, the device showed that thep-type field effect transistor and the current through the source and drain electrodes depend on the buffer pH. The current increases with decreasing pH of the CNT solution. This device, which can detect pH, is applicable for use as a biosensor through modification of the CNT surface

The habu genome reveals accelerated evolution of venom protein genes

Evolution of novel traits is a challenging subject in biological research. Several snake lineages developed elaborate venom systems to deliver complex protein mixtures for prey capture. To understand mechanisms involved in snake venom evolution, we decoded here the ~1.4-Gb genome of a habu, Protobothrops flavoviridis. We identified 60 snake venom protein genes (SV) and 224 non-venom paralogs (NV), belonging to 18 gene families. Molecular phylogeny reveals early divergence of SV and NV genes, suggesting that one of the four copies generated through two rounds of whole-genome duplication was modified for use as a toxin. Among them, both SV and NV genes in four major components were extensively duplicated after their diversification, but accelerated evolution is evident exclusively in the SV genes. Both venom-related SV and NV genes are significantly enriched in microchromosomes. The present study thus provides a genetic background for evolution of snake venom composition

GakuNinMoodle: Toward Robust E-Learning Services Using Moodle in Japan

In this study, we aim to improve security awareness education by developing more robust e-learning services that can maintain itself in the busy period including the beginning of new semesters. This paper focuses on the improvement of e-learning services on Moodle with limited system resources. The course design and Moodle management were improved as follows after some workarounds: (1) The “Final Test, ” which is a JavaScript-based test inside the Shareable Content Object Reference Model (SCORM) content was divided into a Moodle quiz module. “Conditional Activities” were then adopted to allow users to take the “Final Test” after the completion of the SCORM content. (2) The course was reset annually to delete all SCORM tracking data. In this study, we obtain effective operational findings for developing robust e-learning services, particularly for Moodle. As a result, we can provided robust e-learning services in Japan because GakuNinMoodle and the security awareness education course for federated institute, “Learn with Princess Rin Rin: Cyberethics” are accessed by 102 institutes including Kyoto University, Gunma University, and National Institute of Technology through actual operations. In general, database optimization is the best method for improving LMS performance with limited system resources. Specifically, online courses that include SCORM content should be considered as an overhead of API calls between LMS and SCORM content to determine a temporary solution under the constraint of limited resources to improve the performance of LMS when numerous accesses and downloads of learning reports are requested. Therefore, robust e-learning services with Moodle can be obtained even with limited resources. Additional research is being conducted to analyze learning records and system logs to improve the contents according to the assumption that the best method to improve e-learning is by considering learner's behavior