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Networks are critical to the success of the metacomputer. They must transmit data from one computer to another at very high speeds--gigabits or billions of bits every second. If you've got data pouring from a supercomputer like water from a firehose, you don't want to transmit that data to another computer with a garden hose.
Moreover, the networks must transmit all that data reliably, possibly over large distances. Networks bring the power of computers--wherever they may be--to the scientist in the laboratory, the librarian in the library, the physician in the hospital, the student in school. Increasingly, networks must be able to transmit audio and visual information as well as data, and also support interactive applications, including virtual reality.
NCSA uses a number of networking technologies, both local and far-reaching, in support the metacomputing.
The current network "backbone" of NCSA's LAN is provided by a Fiber Distributed Data Interface (FDDI), which uses fiber-optic cable to provide connections, at up to 100 megabits per second, between NCSA's high-end supercomputers and a number of high-speed workstations.
A High Performance Parallel Interface (HiPPI) network provides even faster (800 megabits per second) connections between supercomputers, or between supercomputers and high-end workstations. HiPPI's copper cables are limited to 25 meters in length, so it's generally used to connect high-performance computers in the same building.
Advanced Computation Building
These length limitations notwithstanding, NCSA recently
expanded the HiPPI network beyond its Advanced Computer Building into two
other buildings: its facilities in the Beckman Institute, which house the Numerical
Laboratory and the CAVE; and to the nearby Digital Computer Laboratory.
Beckman Institute Digital Computer Laboratory
ATM networks, which function anywhere from 1.5 megabits per second all the way up to 9.6 gigabits (billions of bits) per second, carry voice, data and video over a single line. But ATM offers more than just potential speed. Past efforts to integrate local and wide area newtorks have been plagued by differences in network architectures and protocols (the set of conventions between communication lines and links to the messages to be exchanged). Incorporation of ATM technology into wide area networks will help eliminate the seams between LANs and WANs.
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Wide Area Networks (WANs) connect computers across cities, region,
countries, even continents. NCSA's local area network, for example, is
connected to the Internet at a "node" in Chicago; the San Diego
Supercomputing Center mostly uses a San Francisco node. The nodes
in turn are connected to each other, and it's through the nodes that all Internet
traffic must pass.
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Originally a federally funded network connecting a relatively limited
number of researchers, the Internet now connects tens of thousands of academic,
commercial and government sites both here and abroad.
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In the U.S., the Internet is fast becoming self-supporting via commercial interests. While the capacity of the Internet backbone (45 megabits per second) is adequate for most applications, it's too slow for the most demanding applications where data rates may approach a Gigabit per second.
Very-High Bandwidth Network Service (vBNS)
This ATM-based network connects all five NSF
supercomputing centers and several other research institutions at speeds
of 155 megabits per second. At these speeds, most applications will run nearly as
quickly as though all the machines were in the same room.
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vBNS is a major artery in another networking experiment called the I-WAY (Information Wide Area Year), a network that links dozens of the nation's fastest computers and advanced visualization environments.
The virtual environments, data sets, and computers reside at sites
connected by 11 networks employing varying bandwidths, protocols, and routing
and switching technologies.
The I-WAY is the first truly national scale high-performance ATM applications-driven testbed. Some of the first users of the I-WAY will demonstrate the network at Supercomputing '95.
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Credits and Copyrights
Virtual Environments Application Map
This application map shows how a distributed virtual reality application involving CAVE and
Immersadesk environments employed the vBNS as part of the I-WAY in demonstrations at
Supercomputing '95 and in subsequent experiments.
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Linked to XUNET was the BLANCA testbed, only recently completed. The BLANCA testbed ran between the University of Illinois and the University of Wisconsin-Madison, and between UCB and LBL, at 622 megabits/second--fast enough for collaborating space scientists to observe data from earth-orbiting satellites and change the paths of the satellites in real time.
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