Hiroyuki Kusumoto

Multicast over satellite

Satellite links have wide area coverage and are used for international backbone links. The Asian Internet Interconnection Initiatives (AI/sup 3/) Project is one of the most operational satellite based R & D networks in Southeast Asia. IP multicast is the important technology for the future Internet. Broadcast capability of the satellite link is suitable for the IP multicast application. Uni Directional Link Routing (UDLR) technology is one of the solutions to provide multicast routing for the Uni Directional satellite link. The paper introduces the UDLR technology which can use the UDL satellite link as the Internet infrastructure, it discusses how to provide wide area IP multicast using UDLR technology, and describes an evaluation of the AI/sup 3/ project. Also, the paper describes an actual application on the AI/sup 3/ multicast network, such as Web cache distribution and distance learning.

Experiments of collecting WWW information using distributed WWW robots

This paper presents the experiments of collecting the documents on the WWW using distributed WWW robots. We propose distributed WWW robots to collect the documents quickly. Our final goal is to collect all of the documents on the WWW in Japan within one day. Currently, eight distributed WWW Robots are running in Japan. The experimental results show that we are able to gain 5.8 to 9.7 times speedup when four distributed WWW robots are placed at different places in comparison with when only one WWW robot is used.

PIM-SM configuration and scalability on satellite unidirectional links

This paper considers satellite unidirectional links having a large number of nodes and discusses the PIM-SM configuration on these links if there is no separate multicast routing information base. Looking closely at the PIM-SM specification documents, we propose a PIM-SM configuration that enables multicast traffic to flow on unidirectional links. We also discuss the scalability of PIM-SM on satellite unidirectional links. We expect that the join/prune message suppression strategy is an important element for scaling PIM-SM on these links.

Drouting architecture: Improvement of failure avoidance capability using multipath routing

Failure avoidance capability is a desired feature for telecommunication networks, such as the Internet. However, not all failures can be promptly bypassed on the Internet because routing systems that are responsible for detecting and avoiding failures cannot detect all failures. Consequently, failures can interrupt internet communications for a long time, such as a few hours. This paper proposes a novel routing architecture called Drouting that enables flexible failure avoidance. In Drouting, routers calculate multipaths from a source to a destination by constructing Directed Acyclic Graphs (DAGs) that include all links in the intra-domain network graph. IP packets carry packet tags that are set by the end host. The packet tags are used to select a network path from the multipath routes. In this paper, the failure avoidance property of Drouting architecture is evaluated through comparison with another proposal, Deflection, using simulations. Simulations were performed on inferred and synthetic topologies. Drouting exhibits similar performance with Deflection in terms of the number of nexthops, the number of paths and the length of paths, while Drouting outperforms Deflection in the probability of success of failure avoidance.

Scaling multicast communications by tracking feedback senders

This paper looks at the message implosion problem that may happen on large-scale reliable multicast communications. We propose that receivers track the senders of recent feedback messages and store them in a list to determine the back-off interval to send a feedback message. We call our proposal tracked sender list (TSL). The issues regarding this proposal are how many receivers to be stored in a receivers list, back-off timer intervals, p.d.f selection, and how a receiver stores itself in its list. We analyzed and simulated our proposal using various parameters values in both networks with equal delay and with heterogeneous delays to show the message suppression performance. The results demonstrate that TSL gives a low number of messages over a wide range of receivers even with a short back-off interval and it is not susceptible to packet losses. Our results also show that TSL performs better than other p.d.fs that is used in message suppression.

The design of OSPF extension for handling unidirectional-links

Internet technology assumes all links are bidirectional, hence it does not take advantage of the broadcast nature of radio frequency communications. RFC3077 based on E. Duros et al. (2001) emulates broadcast connectivity in UDL (UniDirestional Link) and it provides generic solution for all network layer mechanisms. However, this method doesn t support some OSPF based on J. Moy (1998) network topology. We extended the definition of UDL. Our extention enables a node does not have to be reachable from another node. With our extention, we can use every connectivities over UDL as routes then we extended OSPF to handle unidirectional links. Our extension enables all OSPF routers to construct the routing table including UDL, and it is compatible with general OSPF implementation.

Construction of internet for Japanese academic communities

WIDE (Widely Integrated Distributed Environment) is a research project aimed at achieving a transparent distributed environment over heterogeneous distributed computing elements with the consideration of various types of connections for internetworking. The target environment of the research is computing environment in the academic and research communities especially in Japan. The WIDE project started its research activities at the end of 1986. The initial purpose of the group was to design the future JUNET environment. In Japan JUNET has been the only network that provides connectivities among academic and research institutes in both private and public organizations. In order to provide better computer communication with the network, interconnection of networks based on open architecture is strongly required. As the result of various studies, the project started its actual design in late 1987 and has been establishing working environments by connecting several universities with various types of links. Together with the actual state and the future plan of the WIDE project, this paper discusses the overview of technologies being employed for the achievement of project goals such as networking technologies, operating system architecture and name space. As the background status of the WIDE projects, this paper also reports an overview of existing academic and research computer networks in Japan, especially focusing on university environments where the sharing of the large scale computing resources are provided.

Network architecture using network address translation mechanism for network with unidirectional links

In this paper, we present a network architecture using satellite communications (a wide-area unidirectional communication medium) and a ground network (a two-way communication medium) that is effective in an environment exhibiting a trend toward nonsymmetrical traffic, as well as the implementation of such an architecture. Unidirectional data transmission channels have poor compatibility with the existing Internet routing control architecture, and they do not make the best use of wide-band unidirectional links offered by existing routing control techniques used in the satellite communications. In this study, we propose an architecture based on unidirectional links integrated into existing Internet routes that enables the party requesting the data transmission to send, using an address translation mechanism, a query to the sending party using multiple network addresses of satellite and ground links. Effectiveness of the network address translation mechanism was demonstrated by experiments using actual satellite communication links and simulation based on a LAN environment. At the present time, the increasing use of the Internet in residences and small offices leads to increasing traffic, especially in the direction of information acquisition from outside sources rather than from the users to outside networks. The proposed architecture makes it possible to build satellite communication channels representing a wide-area broadcast-type communication medium that can be used as communication routes suited to this increasing traffic trend.