Emerging high-performance applications require the ability to exploit diverse, geographically distributed resources. These applications use high-speed networks to integrate supercomputers, large databases, archival storage devices, advanced visualization devices, and/or scientific instruments to form networked virtual supercomputers or metacomputers. While the physical infrastructure to build such systems is becoming widespread, the heterogeneous and dynamic nature of the metacomputing environment poses new challenges for developers of system software, parallel tools, and applications. In this article, we introduce Globus, a system that we are developing to address these challenges. The Globus system is intended to achieve a vertically integrated treatment of application, middleware, and network. A low-level toolkit provides basic mechanisms such as communication, authentication, network information, and data access. These mechanisms are used to construct various higher-level metacomp...

Modern networked computing environments and applications often require---or can benefit from---the use of multiple communication substrates, transport mechanisms, and protocols, chosen according to where communication is directed, what is communicated, or when communication is performed. We propose techniques that allow multiple communication methods to be supported transparently in a single application, with either automatic or user-specified selection criteria guiding the methods used for each communication. We explain how communication link and remote service request mechanisms facilitate the specification and implementation of multimethod communication. These mechanisms have been implemented in the Nexus multithreaded runtime system, and we use this system to illustrate solutions to various problems that arise when implementing multimethod communication. We also illustrate the application of our techniques by describing a multimethod, multithreaded implementation of the Message Pas...

High-speed wide area networks are expected to enable innovative applications that integrate geographically distributed, high-performance computing, database, graphics, and networking resources. However, there is as yet little understanding of the higher-level services required to support these applications, or of the techniques required to implement these services in a scalable, secure manner. We report on a large-scale prototyping effort that has yielded some insights into these issues. Building on the hardware base provided by the I-WAY, a national-scale Asynchronous Transfer Mode (ATM) network, we developed an integrated management and application programming system, called I-Soft. This system was deployed at most of the 17 I-WAY sites and used by many of the 60 applications demonstrated on the I-WAY network. In this article, we describe the I-Soft design and report on lessons learned from application experiments. 1

This paper discusses the I-WAY project and provides an overview of the papers in this issue of IJSA. The I-WAY is an experimental environment for building distributed virtual reality applications and for exploring issues of distributed wide area resource management and scheduling. The goal of the I-WAY project is to enable researchers use multiple internetworked supercomputers and advanced visualization systems to conduct very large-scale computations. By connecting a dozen ATM testbeds, seventeen supercomputer centers, five virtual reality research sites, and over sixty applications groups, the I-WAY project has created an extremely diverse wide area environment for exploring advanced applications. This environment has provided a glimpse of the future for advanced scientific and engineering computing. 1 A Model for Distributed Collaborative Computing

We describe a software infrastructure designed to support the development of applications that use high-speed networks to connect geographically distributed supercomputers, databases, and scientific instruments. Such applications may need to operate over open networks and access valuable resources, and hence can require mechanisms for ensuring integrity and confidentiality of communications and for authenticating both users and resources. Yet security solutions developed for traditional client-server applications do not provide direct support for the distinctive program structures, programming tools, and performance requirements encountered in these applications. To address these requirements, we are developing a security-enhanced version of a communication library called Nexus, which is then used to provide secure versions of various parallel libraries and languages, including the popular Message Passing Interface. These tools support the wide range of process creation mechan...

Metacomputing systems use high-speed networks to connect supercomputers, mass storage systems, scientific instruments, and display devices with the objective of enabling parallel applications to access geographically distributed computing resources. However, experience shows that high performance often can be achieved only if applications can integrate diverse communication substrates, transport mechanisms, and protocols, chosen according to where communication is directed, what is communicated, or when communication is performed. In this article, we describe a software architecture that addresses this requirement. This architecture allows multiple communication methods to be supported transparently in a single application, with either automatic or user-specified selection criteria guiding the methods used for each communication. We describe an implementation of this architecture, based on the Nexus communication library, and use this implementation to evaluate performance i...

High-speed wide-area networks enable innovative ap-plications that integrate geographically distributed com-puting, database, graphics, and networking resources. The Message Passing Interface (MPI) can be used as a portable, high-performance programming model for such systems. However, the wide-area environment in-troduces challenging problems for the MPI implementor, because of the heterogeneity of both the underlying physical infrastructure and the authentication and software environment at different sites. In this article, we describe an MPI implementation that incorporates so-lutions to these problems. This implementation, which was developed for the I-WAY distributed-computing ex-periment, was constructed by layering MPICH on the Nexus multithreaded runtime system. Nexus provides automatic configuration mechanisms that can be used to select and configure authentication, process creation, and communication mechanisms in heterogeneous systems.

We describe a software infrastructure designed to support the development of applications that use high-speed networks to connect geographically distributed supercomputers, databases, and scientific instruments. Such applications may need to operate over open networks and access valuable resources, and hence can require mechanisms for ensuring integrity and confidentiality of communications and for authenticating both users and resources. Yet security solutions developed for traditional client-server applications do not provide direct support for the distinctive program structures, programming tools, and performance requirements encountered in these applications. To address these requirements, we are developing a security-enhanced version of a communication library called Nexus, which is then used to provide secure versions of various parallel libraries and languages, including the popular Message Passing Interface. These tools support the wide range of process creation mech...

We use the term ubiquitous supercomputing to refer to systems that integrate low- and mid-range computing systems, advanced networks, and remote highend computers with the goal of enhancing the computational power accessible from local environments. Such systems promise to enable new applications in areas as diverse as smart instruments and collaborative environments. However, they also demand tools for transporting code between computers and for establishing flexible, dynamic communication structures. In this article, we propose that these requirements be satisfied by introducing Java classes that implement the global pointer and remote service request mechanisms defined by a communication library called Nexus. Java supports transportable code; Nexus provides communication support and represents the core communication framework for Globus, a project building infrastructure for ubiquitous supercomputing. We explain how this NexusJava library is implemented and illustrate its use with e...

Interactive, immersive virtual environments allows observers to move freely about computer generated 3D objects and to explore new environments. The effectiveness of these environments is dependent upon the graphics used to model reality and the end-to-end lag time (i.e., the delay between a user's action and the display of the result of that action). In this paper we focus on the latter issue, which has been found to be equally important as frame rate for interactive displays. In particular, we analyze the components of lag time resulting from executing a finite element simulation on a multiprocessor system located in Argonne, Illinois connected via ATM to the interactive visualization display located in San Diego, California. The primary application involves the analysis of a disk brake system that was demonstrated at the Supercomputing 1995 conference as part of the Information Wide Area Year (IWAY) project, which entailed the interconnection of various supercomputing centers via a ...