Keita Kawano

A multilevel hierarchical distributed IP mobility management scheme for wide area networks

Hierarchical Mobile IPv6 (HMIPv6) has been proposed as one solution to accommodate the frequent movements of mobile terminals (MTs) in IP-based mobile communication networks. HMIPv6 utilizes a mobility anchor point (MAP) that allows the network to manage the mobility of MTs without causing any overflow of outgoing and incoming messages beyond the network perimeter. However, there is a problem in applying HMIPv6 to a wide area network having a multilevel hierarchy. The distribution of several MAPs within such a network can be used as a means of optimizing the different mobility scenarios experienced by MTs. However, HMIPv6 allows MTs to select their own MAP, so with HMIPv6, the MTs may not select the MAP that would be chosen in an optimized scheme. This may cause load concentration at a particular MAP and/or overflow of signaling messages to and from outside networks. An effective IP mobility management method is proposed that focuses on the speed of movement of the MTs. It reduces the number of signaling messages to and from outside networks without suffering from load concentration at particular MAPs, and we show, by simulation experiments, that the proposed method works effectively.

Multilevel hierarchical mobility management scheme in complicated structured networks

Micromobility management is a key issue for achieving enhanced mobile Internet services. Many micromobility management schemes supporting fast handover, e.g., Hierarchical Mobile IPv6 (HMIPv6), have been proposed to minimize the packet loss during handover and the handover latency. We have previously proposed a multilevel hierarchical mobility management scheme that enhances HMIPv6 mobility management. Our scheme manages the micromobility of a mobile terminal (MT) using a mobility management router (the mobility anchor point, or MAP), with a management domain matched to the MTs mobility. This usage of MAP aims to efficiently decentralize the load of mobility management. In our previous work, we have confirmed the effectiveness of our scheme in a network having a simple tree-based hierarchy. The actual networks, however, have some local variation and/or some redundancy in structure. In such a complicated structured network, the MAP domains intricately overlap each other. This causes difficulty in selecting the MAP suitable for managing the MT mobility because the suitable MAP for an MT changes according to the complicated local conditions. This paper proposes a method to allow an MT to select the suitable MAP for the MT in such a network by adjusting the selection criteria individually configured for use at a particular place. Finally, the performance of our scheme is evaluated using simulation experiments. The simulation results show that our scheme works well in complicated structured networks by using the proposed additional method.

Performance Improvement of SCTP Communication Using Selective Bicasting on Lossy Multihoming Environment

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 influence of surrounding environment such as electromagnetic noise. In this paper, we propose a method to mitigate the impacts caused by packet loss by virtue of SCTP bicasting in lossy multihoming environment with two or more wireless networks. This method bicasts not all packets but only important packets concerning retransmission for efficiency since bicasting all packets would cause congestion. We also implemented a prototype system based on the proposed method. According to the result of performance evaluation experiment, we confirmed the effectiveness of the proposed method by the fact that the prototype system performed faster transmission than normal SCTP transmission even in high packet loss rate environment.

An Execution Control System for Application Software Reducing Administrative Burden of Educational PCs

In recent years, there have been a large number of educational PCs in many universities with the development of computer-assisted teaching. As the number of educational PCs has increased, the burden on the administrators has also increased. In general, these educational PCs have been configured from one or a few model disk images to reduce this burden. This method, however, lacks flexibility of administration. Use of some application software is restricted to specific users or specific sites in the universities. Use of other application software is prohibited by teachers during some examinations. The traditional method does not work well under these conditions. This paper proposes a system to reduce the administrative burden of educational PCs even in those situations. The proposed system controls the execution of individual application software on each educational PC depending on the attributes or the location of users. Teachers as well as administrators are allowed to configure the settings for the proposed system to control the execution of application software dynamically during their class.

Multilevel hierarchical mobility management in densely meshed networks

Micromobility management is a key issue for the deployment of broadband mobile communication services. The packet loss during handover and the handover latency need to be minimized to maintain the high quality of these services. We have previously proposed a mobility management scheme that addresses this issue in wide-area mobile networks that employed hierarchical multiple mobility management routers (Mobility Anchor Points or MAPs). Our scheme directs a Mobile Terminal (MT) to a suitable MAP to fully minimize packet loss during handover, and handover latency of the MTs. In our previous work, we confirmed the effectiveness of our scheme using a simple tree network. Actual networks however, always have densely meshed topologies to provide some redundancy for the elimination of single points of failure. In such networks, it is difficult to deduce the relationships between the MAPs, and this makes it difficult for our scheme to select a suitable MAP for an MT, because the selection is performed using both the MTs smoothed speed and the relationships existing between the MAPs located above the Access Router (AR), to which the MT is connected. In this paper, we propose a method to overcome this problem, by autonomously adjusting the selection criteria that are individually configured for use at a particular AR, and we evaluate this method using simulation experiments. The results show that our mobility management scheme works well in densely meshed networks using the proposed additional method.

A Method of Dynamic Interconnection of VLANs for Large Scale VLAN Environment

VLAN (virtual LAN) is a technology which, can configure logical networks independent of the physical network structure. With VLAN, users in common spaces (such as meeting rooms) can access their department networks temporarily because changing of logical network structure is achieved only by configuration of VLAN switches. However, in the general configuration method, because VLANs are managed statically by administrators, various problems such as high administrative cost and conflict or insufficiency of VLAN-IDs may arise especially in large scale organizations where VLANs are managed by each department. To solve these problems, we propose a method which provides an interconnection between a temporary configured VLAN in a common space and a VLAN of a users department. In the proposed method, a user in a common space can access to his/her department network seamlessly by converting a temporary VLAN-ID in the common space and a VLAN-ID used in his/her department each other automatically. The effectiveness of the proposed method is confirmed by the experiment on the actual network using VLAN managers, VLAN-ID converters and authentication servers based on the proposed method

Target Application Grouping Function Considering Software Updates on Application Execution Control System

In recent years, most large-scale educational institutions like universities have had a large number of PCs for education (educational PCs). Since they are usually identically configured using a centralized management system with image distribution, it is difficult to flexibly provide different environments according to various conditions. To solve this problem, we have previously developed a system (traditional system) to provide individual application software environment virtually on the same educational PC. It controls the execution of application software based on user ID and/or users location. The traditional system, however, cannot handle updates of target application software. This is because the traditional system identifies target application software using the hash of its execution file. It also cannot support grouping of target application software. This paper proposes a new function which detects updates of application software and reconstructs execution rules. With the newly proposed grouping function considering software updates, different versions or types of application software can be managed efficiently with the proposed system.

Access point virtualization for multiple services in heterogeneous WLANs

In recent years, as higher performance terminal equipments are spread, the amount of mobile data traffic is growing rapidly by using popularization of streaming services in wireless networks. To overcome this situation, it is considered that Access Points (APs) are deployed densely for capacity improvement. In such an environment, virtualization is a possible technique to use multiple APs efficiently. In this paper, we assume the environment where macro cells and small cells are co-existing, and BE (Best Effort) users and GBR (Guaranteed Bit Rate) users arrive. Then, we propose a virtual AP configuration method. Specifically, BE and GBR virtual APs are configured with multiple physical APs respectively and the configuration of both virtual APs are changed dynamically at the constant interval. The proposed method achieves reducing the call blocking rate of GBR users and improving satisfaction of BE users.

A flexible execution control method of application software for educational windows PCs

Recently, many educational institutions have had to maintain a large number of PCs (educational PCs). It is common for the administrators of these institutions to use a disk image distribution system to manage them all together. It allows the administrators to keep all of their educational PCs in the same configuration with ease. This method, however, robs them of the flexibility of management. Suppose that use of certain application software is restricted to specific users or sites in those institutions. Suppose also that use of other application software is requested to be prohibited by teachers during classes. It is hard for the administrators to satisfy all of these requirements with the traditional method since it causes heavy administrative burden. This paper proposes a flexible method to manage application software on educational Windows PCs without significant efforts of the administrators even with these requirements. The proposed method controls the execution of individual application software on each educational PC to create the requested environments. Teachers as well as the administrators can directly and dynamically change its configuration during their classes. An execution control system was actually implemented as a prototype to show the feasibility of the proposed method.

Spam Mail Discrimination System Based on Behavior of DNS Servers Associated with URLs

As one of anti-spam technologies, DNSBL based on the URLs or their corresponding IP addresses in the messages is well used. However, some spam mails cannot be filtered by conventional DNSBLs since the spammers create websites using various techniques such as botnet, fast-flux and Wildcard DNS record. To discriminate such spam mails, we ananalyzed DNS record characteristics corresponding to the domain name in the URLs in actual spam mails. According to this analysis, in this paper we propose a spam mail discrimination system based on the behavior of DNS servers. Since the behavior checking process is likely to wait for a timeout, the system queries some records to a DNS server simultaneously and decides whether the mail is spam or not on receiving the first reply. In addition, the system also introduces a blacklist for the IP addresses of the DNS servers.