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Virtual Network: Towards Location

Transparent Communication in Large

Distributed Systems

Fumio Teraoka, Yasuhiko Yokote, and Mario Tokoro

[email protected]

tel: +81-3-448-4380

fax: +81-3-448-4273

Sony Computer Science Laboratory Inc.

3-14-13 Higashigotanda, Shinagawa-ku, Tokyo 141, Japan

June 13, 1990


Advancement of the functionality of portable computers make it more important to provide users with location transparent communication in large distributed systems. This paper divides location transparency into two levels and introduces the concept of the virtual network to achieve the lower level location transparency. To support the virtual network, the network layer is divided into two sublayers. The transport layer can specify a target host by an address which never changes even if the target moves to another network. The increase of network traffic to resolve the address of a moved host is small. And this concept is applied to the IP protocol as an example.

1 Introduction

Many distributed systems provide users with network transparency which conceals the existence of networks and provides users with uniform communication methods regardless of whether the target exists locally or remotely. Recently, portable computers are getting pop-

ular. Although they don't have enough computational and communication functionality yet, the functionality of portable computers might be equivalent to that of current workstations in the near future. Advancement of the functionality of portable computers will increase the demand of user's desire to use their own computers in the same environment regardless of their location in large distributed systems, i.e. users will carry their own computers and connect them to a network at any points in large distributed systems. On the other hand, resources in distributed systems are abstracted as objects. Objects such as processes and files communicate with each other to continue their computation and move across systems to achieve load balancing, high reliability, and so on.

Thus, hosts and objects will move across systems in the future large distributed systems. In such environment, it is needed to provide users with not only network transparency but also location transparency which conceals the location of the target and provides users with uniform communication methods regardless of the location of the target. Al-