Kazuhide Koide

A New Dynamic Scheme for Efficient RTS Threshold Handling in Wireless Networks

Wireless network is an essential and integral part of the ubiquitous environment. For efficient access control, two different transmission schemes are used: The basic carrier sensing multiple access with collision avoidance (CSMA/CA) and request-to-send/ clear-to-send (RTS/CTS) handshaking. The RTS/CTS handshaking addresses the hidden terminal problem as well as reduces the chance of collision in case of higher node density and traffic. However, in networks with low density, basic scheme would lead to higher throughput due to its less overhead. Efficient switching between these two schemes is imperative to maximize the throughput. We have first investigated to find a meaningful threshold value according to the network situation. The proposed algorithm then dynamically adjusts RTS Threshold according to the packet delivery ratio, which is an indicator of network traffic and shows a significant improvement over existing CSMA/CA and RTS/CTS schemes. Our adaptive scheme performed even better when data rates increases. We verify our proposed scheme with extensive network simulation using ns-2.

RUIS: development of regional ubiquitous information system and its applications: towards a universal ubiquitous information

Wide deployment of ubiquitous information environment makes it possible to provide various information to many users. “Regional information” should be one of the most valuable information if “context-aware” provision to community residents is made. But “contexts” of community residents are private information and should be treated very carefully. In this paper, we propose a novel information system called RUIS -Regional Ubiquitous Information System. RUIS can obtain and store regional information from network, realize robust security mechanism of personal/private information protection, and provide information that matches to residents’ contexts. Using RUIS features we can realize“smart watch over” for children. We are working on the implementation of this application based on RUIS prototype.

SNMP in the IPv6 context

Monitoring networks is important for operations, management and security as well as for research and development, but with the rapid pace in which the network is evolving and newer protocols are emerging it is becoming a challenge to monitor new generation networks. We describe the protocol implementation and deployment issues that exist in monitoring IPv6 networks using the Internet management protocol SNMP and then discuss some of the measures taken to work around the issues.

A Bulk-retrieval Technique for Effective Remote Monitoring in a Mobile Environment

For effective management it is necessary to have methods by which management applications can periodically retrieve large volumes of information from network devices. In this work we examine the issues related to standards-based bulk-information retrieval and then propose a technique that extends the limits of periodic bulk-retrieval. The impact of the technique is demonstrated using a prototype implementation with special emphasis on network monitoring, traffic management and security management by comparing with the widely used RMON technology. We then discuss the problems of monitoring in a mobile environment in the context of the newly defined IETF standards track mobile IPv6 management information base (MIPv6MIB) and show how the bulk retrieval technique can be used to provide a mechanism for reliable monitoring in a mobile environment

MobiSNMP--A Model for Remote Information Collection from Moving Entities Using SNMP over MobileIPv6

The advent of mobile IP communication has opened up several new areas of mission critical communication applications. But the bandwidth and reliability constraints coupled with handover latency are posing some hurdles which need to be overcome before real world mobile IP applications, with low tolerance for data loss, can be deployed. In this paper, we analyze the unreliability of existing information collection methods in the real-world MobilelP environment. We focus on this problem and propose a novel network management model that anticipates the wireless mobile entities and uses SNMP. The key idea of this model is the introduction of a store-and-forward type Managed Object (MO). During the period of unreachability between the Manager and the agent, the data is cached at the agent until the connectivity recovers. In our experiment we used a prototype implementation in real-world wireless communication field, and showed the effectiveness of our proposed method.

Management for Mobility-Aware Networks Based on Standardized Protocols

In the traditional network management architecture, there is an implicit assumption that a managed device will not change its location. Location related information where available is static, and it is used for simple reporting purposes. However with mobile devices these attributes are inherently dynamic. Monitoring processes of management information also encounter difficulties of network instability caused by roaming of devices or wireless signal errors. So the current approach of network management needs to be reviewed. MobileIPv6 and NEMO are standardized protocols for realizing mobility-aware network. In this article we propose new network management technologies for MobileIPv6/NEMO network based on the Internet standard network management protocol, Simple Network Management Protocol (SNMP). Our focus is the importance of 1) location awareness and 2) intelligent monitoring process. We explained about the MobileIPv6/NEMO-MIB that is aware of mobile device’s dynamically changing location. We also propose the delayed data sending method that realizes effective transfer of management information without congestion over an instable network. From an evaluation in simulations, and experiments in real environment, we confirmed that our approach is effective for improving monitoring processes for mobile devices in management of MobileIPv6/NEMO network. This is one of the first management applications that are completely based on Internet standard protocols of MobileIPv6/NEMO, and SNMP.

TCP retransmission monitoring and configuration tuning on AI 3 satellite link

The AI3 project aims to achieve effective and fair bandwidth usage of its relatively narrow satellite links by all the partners in this project and the best possible end-to-end communication quality under limited resources. It is difficult to realize them as the operation of it is shared by all the partners with heterogeneous traffic demands and policies, as the network includes many traffic engineering(TE) facilities for traffic shaping or priority queuing in various points. In this paper we monitor the retransmission rate of TCP flows in a passive mode to obtain estimated packet loss rate of each flow and partner, and try to analyze the actual reason that affects end-to-end communications in a real-world environment. The results obtained in this paper is considered as a first step of reflecting TCP retransmission monitoring to improve operation, focusing on a certain partner, ITB, who has the largest traffic demand in AI3. The effectivity of the method is approved by the experimental configuration tuning.