Self-tuning software speeds networks

By Eric Smalley, Technology Research News

As the Internet speeds up, the standard software that guides information across the net may not be able to keep up.

Many computers connected to the 100-megabits-per-second Next Generation Internet (NGI) thatís just taking shape at universities and research centers may see faster transmissions because the Transmission Control Protocol (TCP) software on most computers can't tell the difference between fast and slow networks and is set for the slower ones.

A joint research project of the Pittsburgh Supercomputing Center, the National Center for Atmospheric Research and the National Center for Supercomputing Applications is aiming to remedy the situation by giving TCP the ability to adjust to different networks and network conditions.

Using today's standard TCP settings would result in a computer connected to a 100 megabits-per-second (Mbps) network would achieve only four megabits per second over a cross-country link, according to Matt Mathis, network research coordinator at the Pittsburgh Supercomputer Center. And though it is possible to manually adjust the settings, changing network conditions and differing application needs make automatic adjustment necessary, he said.

TCP breaks data streams such as email messages into small "packets" and hands them to the Internet Protocol (IP) for transmission across the network. On the receiving end, TCP collects the packets and puts them in the correct order, restoring the original data stream.

"There are a couple of system parameters for TCP [that] fundamentally effect how TCP performs over a long link," said Mathis. For instance, "TCP has to have enough buffer space to hold twice the amount of data in flight in order for it to... either retransmit lost packets or deal with congestion." In order to take advantage of high-speed networks today, "you need to manually tune these buffers," he said.

The situation is akin to selling automobiles that lack automatic transmissions, dashboard indicators and diagnostic ports for mechanics, Mathis said. "All three of those functions -- the automatic adjustment for routine problems, the clear controls that the user understands for everyday use, and the diagnostic interface for an expert -- are badly needed by TCP implementations today," he said.

Researchers and other people using high-speed networks can get around problem by manually adjusting buffer sizes. "If you know a machine is a single user machine, then it's not a big deal to arbitrarily set [large buffers]," Mathis said. Although this can cause problems for interactive applications, it works for FTP and Web browsers, he said.

"The problem is if you... use it as a Web server with thousands of connections on it, it runs out of memory," he said.

"This is like Detroit manufacturing cars which are shipped in first gear and... you have to open the hood to change gears. It shouldn't be this way."

The Web100 Project software uses TCP's congestion feedback information to determine network conditions and automatically adjust the sizes of the transmit and receive buffers.

Meanwhile, other researchers are working on new versions of TCP.

"It's certainly true that TCP suffers from various problems," said Venkat Anantharam, a professor of electrical engineering at the University of California in Berkeley. "There are literally dozens of projects studying various aspects of that."

The Web100 Project researchers aim to complete their work in three years. The project has three phases. The first phase is developing in testing the software, the second phase is determining if the software solves people's problems, and the third phase is working with computer vendors to get them to adopt it.

The project is funded by the National Science Foundation and Cisco Systems, Inc.

Timeline:   3 years
Funding:   Government; Corporate
TRN Categories:   Networking
Story Type:   News
Related Elements:   None


November 22, 2000

Page One

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Self-tuning software speeds networks

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