Kiyohiko Okayama

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Multihomed network is one of the most efficient configuration to improve response time of network services. However, it is hard to introduce or manage because the existing configuration methods have several problems in that they require much technical skill, involve administrative over-burden for the administrator aiid so on. In this paper, we propose a(More)
In recent years, spam mails intending for ``One-click fraud" or ``Phishing" have become increasing. As one anti-spam technology, DNSBL based on the URLs or their corresponding IP addresses in the messages is well used. However, some spam mails that cannot be filtered by conventional DNSBLs get appearing since the spammers create websites using various(More)
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(More)
NAT (Network Address Translation) is well-known as one of the short-term solutions of IPv4 address exhaustion. NAT is a technique that shares a single IP address in several PCs, and is widely used for alleviating the IPv4 address exhaustion and as a security solution. However, when a backbone network has access control function for PCs based on their IP(More)
NAT (Network Address Translation) is widely used as a technique that shares a single IP address in several PCs, and is widely used for alleviating the IPv4 address exhaustion and as a security solution. However, when a backbone network has access control function for PCs based on their IP addresses, it can not identify the PCs behind a NAT router since(More)
Wavelength Division Multiplexing (WDM) technology provides a wideband communication networks by realizing multiple communication channels with different wavelengths on a single optical fiber. In this technology, each node (wavelength router) has a finite number of transmitters/receivers dealing with different wavelengths, where each wavelength is(More)
With the explosive widespread of the Internet, many fundamental and popular Internet services such as WWW and e-mail are becoming more and more important and are indispensable for the human's social activities. As one technique to operate the systems reliably and efficiently, the way of introducing multihomed networks attracts much attention. However,(More)
In recent years, with proliferation of smart phones and tablet PCs, speedup of wireless LAN communication is required for dealing with increase of traffic in wireless networks. However, transmission speed through a wireless network often slows down in comparison with that through a wired network since packets of wireless networks frequently drop due to the(More)
Recently one of sender authentication methods called SPF is getting popularized as an anti-spam technology. However, SPF has a problem in terms of that the forwarded e-mails can not be authenticated correctly. In this paper, we propose a solution for SPF on forwarded e-mails by tracing recipient addresses in ``Received" fields of e-mail header without(More)