TECHNOLOGY; Multimedia Transmissions Are Driving Internet Toward Gridlock
By SARA ROBINSON
Published: August 23, 1999
Like a nation's highway system, the Internet has traffic rules that prevent chaos and gridlock. But an increasingly popular type of multimedia traffic is turning out to be a cyber road hog that flouts the rules and creates traffic jams.
This scofflaw traffic, known as streaming media, is widely hailed as the future of home entertainment, capable of eventually delivering high-quality audio and video programming over the Internet.
Unfortunately, network experts warn, it may drive everyone else off the road.
Streaming media is analogous to broadcast media in that the audio or video material is produced as soon as a computer receives the data over the Internet. The problem is that the streaming data does not respond to network congestion in the way other Internet traffic does.
When a computer sending conventional data encounters congestion, it significantly slows its own transmission rate, but a computer sending streaming data will reduce the flow only slightly. So if streaming traffic competes with conventional traffic for the same congested strip of roadway, the streaming traffic, like some V.I.P. motorcade, just assumes the right of way and lets all other data traffic pile up.
The difference, said Van Jacobson, chief scientist for Cisco Systems Inc., a leading maker of Internet traffic routers, is that conventional traffic ''is polite; this stuff is impolite.''
''People writing software for that traffic -- they don't care,'' Mr. Jacobson said of streaming media. ''In the long term, it's a problem.''
By its very nature, streaming media has to flow continuously to the user's computer, so it cannot follow the same traffic rules as conventional data. But even so, it is possible for packets of streaming data to interact civilly with other traffic on the Internet. The reason they do not, Mr. Jacobson said, is that streaming media providers have no incentive to comply with traffic rules.
Today, he said, ''if Real Networks is polite and Microsoft isn't, then Real looks crummy.''
Even elbowing all other data aside, today's streaming media produces a very low quality of entertainment most of the time.
Much of that lack of quality today is due to slow modems at the user's end. In three to five years, when cable modems and souped-up digital telephone lines are expected to be common, most Internet users may be listening to live Webcasts or playing high-quality radio on their computers. In 10 years, movies and commercial television might very well be carried over Internet channels.
This increasing demand will add vast amounts of streaming traffic to the Internet and could lead to what Mr. Jacobson calls ''congestion collapse'' -- the Internet equivalent of gridlock.
Internet service providers are also concerned.
Tony Blake, vice president for marketing and business development for AT&T Labs Research, calls the trend disturbing, adding, ''What people are saying is, 'If my stuff gets through, that's all I care about.' '' He said AT&T and other Internet service providers were pressuring the producers of streaming media to head off the problem before it grows out of control.
Streaming media traffic is also of growing concern to the Internet Engineering Task Force, an industry group that is the closest thing the Internet has to a governing technical body. Mr. Jacobson, an active task force participant, said the group has not yet formally addressed the issue because ''it's not big enough to kill the Net.''
Not yet anyway. But a number of Internet service providers are getting nervous.
Mr. Jacobson said he would like to see streaming media use congestion controls that are compatible with those used for conventional data-packet traffic.
Today, according to measurements by the National Laboratory for Applied Network Research at the University of California at San Diego, none of the existing streaming media providers are using such controls.
Real Networks, the largest streaming media provider, declined to respond to the growing criticism, although a spokesman, Jay Wampold, said the company was trying to address congestion problems. Over the last year, he said, Real Networks had installed a network of computers for delivering the company's broadcasts that bypasses the Internet's main traffic routes.
Kevin Unangst, lead product manager for Windows Media, the streaming media division at the Microsoft Corporation, said the company was working with network companies to route its streaming data around the Internet's main arteries.
''We know bandwidth and optimizing bandwidth is a huge, huge issue,'' Mr. Unangst said, using an industry term for transmission capacity, ''and we're covering all the bases.''
But Mr. Jacobson said that while actions like those taken by Real Networks and Microsoft might help, they would not resolve the problem. The bottlenecks are not on the main thoroughfares, he said, but on the side streets and access roads.
''As you get out to the edge of network, closer to users, that's where the bandwidth gets limited,'' he said.
While cable modems and digital subscriber lines will increase bandwidth to the home, a truly significant increase in Internet bandwidth would require ripping out 300 million copper wires and replacing them with fiber.
''That's not going to happen fast,'' Mr. Jacobson said.
The remedy, experts say, lies in providing incentives for streaming media providers to comply with traffic rules.