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...

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...

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...

Emerging telemedicine applications require the ability to exploit diverse and geographically distributed resources. High-speed networks are used to integrate advanced visualization devices, sophisticated instruments, large databases, archival storage devices, PC's, workstations, and supercomputers. This form of telemedical environment is similar to networked virtual supercomputers also known as metacomputer. Metacomputers are already being used in many scientific application areas. In this article, we analyze requirements necessary for a telemedical computing infrastructure and compare them with requirements found in a typical metacomputing environment. We will show that metacomputing environments can be used to enable a more powerful and unified computational infrastructure for telemedicine. The Globus metacomputing toolkit can provide the necessary low level mechanisms to enable a large scale telemedical infrastructure. The Globus toolkit components are designed in a modular fashion and can be extended to support the specific requirements for telemedicine.