NASA finds Internet
Many, especially those in developing countries, may
never get linked.
By Jube Shiver Jr.
Los Angeles Times
WASHINGTON - In a significant setback for the satellite industry, NASA
scientists have discovered that a key transmission standard that is the
foundation of communications over the Internet and corporate computer
networks does not work well in space.
The discovery could delay the satellite industry's ambitious efforts to
offer high-speed Internet access to companies with remote plants or
offices, as well as to Pacific Islanders and millions of others who can't log
on.
During the next decade, the satellite industry plans to spend more than
$20 billion to extend modern communications services such as telephone,
video programing and computer networks to remote regions.
If satellites cannot be made to work seamlessly with the Internet, tens
of billions of dollars in additional investment in land-based transmission
lines would be required instead. Many developing countries may never
get connected.
"Allowing satellites to be a part of the Internet would provide huge
benefits to companies and individuals - if we could make it work," said
Daniel R. Glover, a National Aeronautics Space Administration project
engineer in Cleveland who has been spearheading the investigation into
the problem.
The TCP, or Transmission Control Protocol, problem arises because of
the vast distances the data must travel to reach satellites.
Electronic data can take as long as a half a second to travel up and down
to Earth from geostationary satellites 25,700 miles up. Although that kind
of delay only causes a slight echo when placing a telephone call, for
example, it can wreak havoc when two computers are trying to
communicate.
That's because the delay causes TCP to believe there is a backup in the
network, which in turn disrupts the electronic acknowledgements the
receiving computer sends to confirm that messages are being received
correctly.
In one NASA experiment, a super-fast technology that normally sends
data at 155 megabits per second over fiber-optic lines was slowed to just
10 megabits per second when NASA used a satellite communications
network.
Teledisc, a Kirkland, Wash., company, is developing a $9 billion
low-Earth-orbiting satellite system that it believes can overcome the
problems.
However, Shawn Ostermann, an assistant professor in the electrical
engineering and computer science department of Ohio University, said his
research found even satellites orbiting closer to Earth can be adversely
affected.
Internet operators say they will oppose any changes that solve the
satellite problem but hurt performance over regular phone lines.
"It would not be an acceptable solution to degrade the current
performance of TCP in order to improve it for satellite use," said Fred
Baker, a software executive at Cisco Systems Inc., who is chairman of
the Internet Engineer Task Force, a standards-setting body. "We don't
want to break it just so somebody in New Caledonia can have better
Internet access."
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