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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)
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)
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)
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)
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 order to improve TCP performance, a method using a PEP (performance enhancing proxy) is proposed. The PEP operates on a router along a TCP connection. When a data packet arrives at the PEP, it forwards the packet to the destination host, transmits the corresponding ACK (premature ACK) to the source host in behalf of the destination host and stores the(More)
Delivering e-mails without unnecessary delay is one of the very important issues as the spread of e-mail service and its use become very common. But in case that a "mail transfer agent (MTA)" is heavily loaded by huge amount of mails sent to the MTA, not only the delay on mail delivery is inevitable but also managing the MTA service becomes difficult. Thus,(More)
VPN (virtual private network) is one of the most important technologies on the Internet. With VPN, we can securely access to resources in the organizational network via the Internet. In VPNs having hierarchical structure, since each VPN domain has different access policy (whether VPN gateway should perform authentication, data encryption, and so on or not),(More)