As the Asynchronous Transfer Mode (ATM) technology comes to be used widely, the Telecommunications Management Network (TMN) over ATM networks becomes an important issue. Since TMN uses the OSI protocols including the Common Management Information Protocol (CMIP), it is required to implement CMIP communication over ATM networks. In order to realize OSI over ATM, ITU-T SG13 has standardized the Service Specific Coordination Function for Connection Oriented Network Service (SSCF-CONS), Service Specific Connection Oriented Protcol (SSCOP), and the Synchronization and Coordination Function (SCF). We have developed the CMIP software over ATM networks adopting these protocols. The CMIP software is designed so that it achieves both high throughput for large data transfer and short response time for small message exchange. The software adopts the implementation mechanisms commonly applied for protocol modules to reduce the overheads for controlling OSI protocol modules, and some protocol specific mechanisms especially for protocols with heavy processing overheads, i.e. SSCOP and CMIP. The performance evaluation shows that the developed CMIP software achieves more than 200 message exchanges per second for messages whose length is 64 Byte long, and achieves about 36 Mbps throughput for transferring data whose length is more than 100 KByte.

According to the wide spread of mobile computer terminals, it is required to connect them to remote networks and to allow them to communicate with home computers and Internet servers. There are some mechanisms studied on the IP terminal mobility, including DHCP which assigns IP addresses dynamically and Mobile-IP which supports seemless mobility. However, there are some problems identified for those methods on compatibility with existing IP terminals, route optimization and compatibility with firewall systems. So we have proposed a virtual subnetwork system which can accommodate existing IP routers and terminals without any modifications, and which selects an optimal route for the communication with networks other than the home network. This paper describes the mechanism and the results of implementation of our system.

Cognitive radio, which utilizes the radio frequency spectrum efficiently by recognizing radio resource availability, is an attractive technology for overcoming the shortage of radio frequency. From the perspective of networking, cognitive radio technologies are also useful since they allow flexible network construction. This paper proposes base station networks using cognitive radio technologies. In order to achieve efficient utilization of the radio frequency spectrum and flexible network construction, we also propose a topology management and route control method for our proposed base station network. Our method shares the status of the wireless links along with topology information and establishes routes by using this information. Through simulation, we evaluate that our method significantly improves the throughput by efficient utilization of the radio frequency spectrum. Moreover, we demonstrate that our method works well when the size of the network gets larger.

Broadband fixed wireless access (BFWA) systems with multi-hop mesh topologies have attracted considerable attention as a promising technology for next generation, high quality, high capacity, and high density access infrastructures. The primary advantages of mesh network topologies are an improvement of capacity by means of traffic engineering throughout the networks. This paper discusses an adaptive traffic load balancing method that maximizes the capacity for the mesh BFWA networks. Taking into account the variation of network conditions such as traffic demand distributions and qualities of wireless links, the adaptive traffic load balancing method attempts to equalize the utilization of capacity for each wireless link. To avoid deteriorating the performance of TCP communications, the proposed method implements flow-based traffic load balancing. Performance of the proposed adaptive traffic load balancing method is demonstrated and validated using the experimental mesh network environments with wired networks with up to sixteen nodes that emulates the variation of the wireless link capacity.

In the Mobile IP handoff procedure, mobile node movement is detected from advertisements of foreign agents that differ from previously received advertisement and the new "care-of" address is registered with the home agent. However, user packets are not forwarded to the new foreign agent until a registration is completed and this interruption may degrade the quality of service especially in real-time applications such as audio and video, or may lower the TCP throughput due to retransmission timeout. To tackle these issues, we propose a new low latency handoff method, where access points used in a wireless LAN environment and a dedicated MAC bridge are jointly used to alleviate packet loss without altering the Mobile IP specifications. In this paper, we present design architecture of the proposed method and evaluate its performance in an actual network environment to verify the effectiveness of our approach.

Nowadays, many IP based communication systems are connected by high-speed networks to realize high-speed TCP/IP communication. However, since the mechanism of TCP/IP protocols is based on a best effort service, the quality of the communication may change by the time or the route of the traffic. Therefore, it is important for network providers to investigate the quality of their users' communication. In order to analyze the traffic on an Internet backbone, the realtime analysis is one of the important factors. So far, several tools were developed for the purpose of the traffic measurement. However, none of them can analyze sufficient statistics to evaluate the quality for each end user's communication in realtime. Therefore, we have designed and implemented a performance monitor, which collects the statistics representing the performance such as TCP throughput while capturing the traffic. The statistics are collected by every pair of IP addresses and by every application. The monitor also provides the function to analyze effectively for the statistics records such as sorting and filtering of the records and the graphical user interface to operate the software tool. This paper describes the design and implementation of the performance monitor.

Broadband fixed wireless access (BFWA) systems with multi-hop mesh topologies have attracted considerable attention as a promising technology for next generation, high quality, high capacity, and high density access infrastructures. The primary advantages of mesh network topologies are an improvement of availability in connectivity between pairs of nodes by means of diversity routes. This paper discusses wireless node architecture that enables the integrated control of route diversity and traffic engineering together with the control of wireless links whose quality and performance could be affected by radio propagation conditions. Taking into account the functional requirements for multi-hop mesh BFWA networks, such as adaptive link configuration with multiple channels, distributed network management, and traffic engineering in mesh networks, the entity called network control unit (NCU) is designed and developed on a common UNIX based server computer. Implemented functions and their performance are demonstrated using the experimental environments with wired networks.

In the gauge of IMT-2000, Mobile IP based location management is standardized. The cellular network of IMT-2000 holds many users and covers a large area. In large-scale Mobile IP networks, such as IMT-2000, a foreign agent may manage many mobile nodes by the visitor list and its forwarding performance degrades owing to the list search overload. In this paper, we propose a fast data transfer method in Mobile IP networks by reducing the load of the search processes on the foreign agent using cooperation between mobility agents. In our experiments, we measured the packet forwarding performance and the packet forwarding process time. The results indicate the possibility of the performance degradation owing to the part of the registered mobile nodes in the visitor list. We verify that the foreign agent using our method can forward all the received packets on Fast Ethernet LAN when one million entries are recorded in the visitor list.

It is widely recognized that IP-based mobile network will be a dominant trend. For mobile IP networks, the address starvation problem and scalable mobility management for mobile nodes are important issues. In order to cope with these issues, we propose an approach to realize mobile IP network supporting private addresses for mobile nodes. Our approach introduces regional registration of mobile nodes (Hierarchical Mobile IPv4) and coordinates NAT and DNS functions with the Mobile IP protocol. It enables a mobile node to be assigned a global address temporally in a visited network and to accept a call initiated by a correspondent node connected to the global IP network. This paper describes the detailed design of our approach and the implementation of proposed procedures based on the Mobile IPv4 software developed by the CMU Monarch project.