SUNNYVALE, Calif. — Two years ago this month, when Victoria's Secret first broadcast its fashion show online, many would-be viewers looking for scantily clad models met with network congestion instead.
Subsequently, the company upgraded its distribution systems to bypass some of the Internet's many choke points. Capacity improved tenfold. Last May's Webcast was much smoother.
The Webcasts exposed more than underwear: They underscored the challenges of bringing quality video and audio to a network designed for text. Difficulties remain even as computers get more powerful and more households get high-speed lines.
By now, Internet users are accustomed to jerky and flickering video images and music recordings that skip like a scratched vinyl record. It doesn't have to be that way.
As the demand for sight and sound explodes, entire businesses, such as iBeam Broadcasting Corp. in Sunnyvale and Akamai Technologies Inc. in Cambridge, Mass., have formed around tweaking Internet performance.
IBeam's production facilities in Silicon Valley look like a cross between a traditional broadcast studio and a network operating center. The blend reflects iBeam's goals of layering a broadcast-style network over an Internet built for other things.
"The Internet was designed to allow scientists to share big data sets reliably," said Tom Gillis, a senior vice president at iBeam. "The thing great about it for distributing Web pages is the thing not great about it for distributing video."
After all, the Internet wasn't built for the direct transmission of data but rather as a way for data to reach destinations in the event a nuclear attack knocked out several major U.S. cities.
If part of the Internet breaks down, data can usually find another path. If a packet or two of data get lost in transit, the browser can request a replacement.
That approach is inadequate, however, for time-sensitive applications like video and audio. Often, the show must go on. It can't wait for data to find another path or get sent anew.
Unlike telephone networks, where you generally get a reliable connection for the duration of the call, the Internet is a "best effort" network.
When one segment hands off traffic to another, the second promises only to make its best effort at delivering those data packets. Data can get delayed or lost at congested "intersections" along the way.
A 1998 Bell Labs study found packet loss of 3 percent to 14 percent for video. Three percent may not sound like much, but it means as much as 30 percent degradation in video quality.
By far the biggest congestion point remains the connection to the home.
But even as households upgrade to high-speed DSL or cable modem links, congestion is merely moved to the center of the network, said Abhi Chaki, a vice president at Edgix Corp. in New York.
Edgix attempts to bypass those points by bringing video, audio and data closer to the home — to the network's "edge." Edgix computers fetch copies of popular programs and distribute them via satellites to some 100 points near the service providers that reach the homes.
It's a similar approach to iBeam's.
Engineers are already working on adding "quality of service" features to tag data packets so that Internet "traffic cops" would know to deliver video and audio ahead of e-mail.