The Great East Japan Earthquake, which occurred in March 2011, damaged information infrastructure. Latest researches showed that some parts of communication networks are available even immediately after the earthquake. Therefore, connections among the different available parts of communication networks can keep communication quality for damaged areas at disasters. Recently, “Software-Defined Networking (SDN)” is one of the up-and-coming network configuration technologies. SDN is useful for the network operation and connection quality at disasters. This paper describes the problems of the information infrastructure at disasters, proposes a network operation method at disasters using SDN to keep connection quality for disaster areas and implements the proposed method.

Computer network security is one of the important issues in the Internet age. Network administrators of organizations such as companies or universities filter IP packets at network equipment such as Layer 3 switch or firewall between their organizations and the Internet to keep the security of the computer networks. One of the expressions of the filtering rules of IP packets is access control list. Access control lists are lists of rules, which describe permission or denial of packet transition based on source IP address, destination IP address, port numbers and so on. Access control lists are not always fixed; network administrators change access control lists according to the change of network topology or network security policy. After several changes, access control lists may include redundancies and network administrators have to modify the access control list to remove redundancies. This modification must keep the semantics of access control list. After modification, the network administrators must confirm that the semantics of access control list does not change. One of the methods of equivalence of two access control lists is to send test IP packets to the network equipment that filters IP packets and to check the transitions of the IP packets. This paper proposes the method of generating test packets to confirm the equivalence of two access control lists.

This paper applies Tesseract-OCR, optical character recognition software, to image spam mail filters. Tesseract-OCR can be specific to a certain language and this paper makes Tesseract-OCR specific to spam words. This specialization decreases times and CPU power that it takes to check whether images of mails include spam words. This paper examines the ability of the spam mail filter of Tesseract-OCR by experiment.

Today e-mail is a indispensable communication tool because of wide spread of Internet technology and many spam mails are delivered in the Internet. In order to avoid spam mails, spam filter is used in many mail servers or PC. It checks the content, sending address or so on of a mail and decides whether the mail is a spam mail. After spam filter works well to remove spam mails, spam senders improve the methods of sending spam. Spam filter technology and spam sending method make a vicious circle. Ending this vicious circle needs spam mail characteristics including the change according to spam filter improvement. This paper analyzes spam mails which are saved in the long term in order to obtain spam mail characteristics and reports the result of this analysis.