Data transfer demo sets speed mark

By Kimberly Patch, Technology Research News

Researchers from Northwestern University and the University of Illinois at Chicago have set a new speed record for transmitting data: 2.8 gigabits, or billion bits, per second. The researchers set the record while transmitting information between Amsterdam and Chicago at the iGRID 2002 conference in Amsterdam on September 24.

The high-speed networking technology is a component of grid computing, which allows people to tap computer power and resources like databases from computers distributed around the world. The speed makes it possible to work with very large amounts of remote data, much like the Web's Hypertext Transfer Protocol makes it easy to access and interact with remote documents.

The record data rate is equivalent to transmitting 350 million characters, or 700 books, per second. Each character requires eight bits, or one byte. The standard protocol used to send information over the Internet is around 500 times slower, even over fast fiber-optic lines.

The researchers carried out the feat by combining three data protocols, or communications layers. The combination forms a software architecture the researchers dubbed Photonic Data Services.

These layers are Photonic Path Services, the Simple Available Bandwidth Utilization Library (SABUL) network protocol, and Data Space Transfer Protocol (DSTP).

Photonic Path Services set up, check the status of, and tear down the photonic paths, or particular routes in an optical data network that the data will take, said Robert Grossman, director of the Laboratory for Advanced Computing and National Center for Data Mining at the University of Illinois at Chicago."Applications can request specialized photonic paths as they are needed," he said.

The network protocol moves bits over long-haul networks. It combines a more efficient data protocol -- user datagram protocol (UDP) -- with the standard and reliable Transmission Control Protocol (TCP) used by the Internet, said Grossman.

The Data Space Transfer Protocol does for data what the Web's Hypertext Transfer Protocol does for text. It makes it as easy to work with remote databases as it is to work with remote documents. The protocol enables users to mine and analyze data that's stored on computers distributed throughout a network, said Grossman. "DSTP is compatible with Web services, but also has specialized functionality to work with data -- it supports keys, metadata and data, [and] can sample data, select rows and columns of data, et cetera," he said. Database operations like queries have traditionally been the most difficult for Grid applications to work out.

The three layers work together like this: the network layer provides the speed to access large amounts of data quickly, the data transfer layer gives users the ability to execute functions on that data, and the photonic path layer gives them the flexibility to do this on a per-application basis, said Grossman.

The combination of layers one and three -- Photonic Path Services and Data Space Transfer Protocol -- allows users to work with remote data sets as large as several gigabytes as if they were local, and even work conveniently with remote terabyte-size data sets, said Grossman. A gigabyte of data is one billion characters, which would fill 2,000 books; a terabyte is one trillion characters, which would fill 200,000 books.

In prior work, the researchers combined the second and third layer and showed they could transfer data as fast as 622 megabits, or million bits, per second, but the conference marked the first time all three layers were combined to produce higher data-transfer rates, said Grossman. "At iGRID for the first time we showed that new implementations of [the network protocol layer and data transfer layer] could scale to 2.8 gigabits" per second and could be integrated with the Photonic Path Services layer, he said.

The Internet's Transmission Control Protocol does not work at very high speeds on long haul networks because the protocol requires acknowledgment of each packet of information. When a file is transferred from one computer to another over the Internet, it is broken up into many packets, which can take different routes to go from one computer to another. The packets are reassembled into the file at the end of their travels. Acknowledging each packet makes the protocol reliable, but "limits the bandwidth to be a function of... the time required to send a packet and receive an acknowledgment," said Grossman.

Transmission Control Protocol can be made to work faster by using multiple network connections, but still tops out at about 155 megabits per second, said Grossman. This works out to about 31,000 bytes, or characters, or about a third of a book.

The researchers' Sabul network layer uses the fast User Datagram Protocol that does not require acknowledgment from the receiving computer in order to send data at high rates. As data arrives, the receiving computer sends information about packet loss using a separate channel and Transmission Control Protocol, and the sender dynamically adjusts its sending rate based on the packet loss numbers in order to minimize lost packets.

The system can achieve 900 megabits per second through a 1-gigabit-per-second network interface card, said Grossman. Using clusters of computers connected to a router through 1-gigabit-per-second links, the researchers were able to send information at 2.8 gigabits per second over the long haul network from Amsterdam to Chicago, he said.

The method could prove valuable initially for industries that need large data flows, said Joe Mambretti, director of the International Center for Advanced Internet Research and at Northwestern University. These include bioinformatics, medical imaging, digital industrial design, financial services and drug design, he said. The protocols could be applied practically within six months, he said.

The 2.8 gigabit-per-second speed from Chicago to Amsterdam is impressive, said Mario Gerla, a professor of computer science at the University of California at Los Angeles. Although the basic ideas the researchers tapped have been used before, the way they put the scheme together is new, he said. "What is novel here is the bringing together of all these known technologies and efficiently integrating them to support a meaningful, important application."

Key to the method's success are the ideas of using dedicated network paths and using fast User Datagram Protocol for data transport, then taking care of error correction and loss recovery at the application level, said Gerla. "The simplicity is key to its success," he said.

There is work to be done, however, to allow the scheme to operate on a packet-switched network like the Internet rather than dedicated lines, he said.

At the same time, there are parallel efforts to extend Transmission Control Protocol to make it work for Grid computing, Gerla said. "There is currently very active research in the area of TCP for gigabit channels over long connections," he said.

The researchers are currently working on optimizing the method, and are working on ways to implement the protocols in next-generation all-optical networks, said Mambretti. "We are also developing new techniques for network service provisioning," he said. These would allow network companies to offer the services to their customers.

The research was funded by the National Science Foundation (NSF), the Advanced Photonic Network Testbed (OMNInet), and Nortel.

Timeline:   6 months
Funding:   Government; Corporate
TRN Categories:  Networking; Internet; Telecommunications
Story Type:   News
Related Elements:   None


October 30/November 6, 2002

Page One

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Data transfer demo sets speed mark

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Microwave drill melts concrete


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