"We were pretty worried," concedes Steven Goldman, F5's sales and marketing vice president. NASA's last try at demonstrating its prowess over the Internet, for the Mars Pathfinder landing, turned into something of a public-relations disaster for the agency when its Web site faltered under the crush of viewers. "This time," says Mr. Goldman, whose company wasn't involved in the Pathfinder debacle, "We helped them pull it off."

Coping with sudden explosions of Web activity has become a touchy and growing problem for Web sitesand their service providers. And the traffic jams are likely to get worse as growing numbers of consumers move onto the Internet, analysts say.

That has made traffic management one of the hottest parts of the data-communications industry, a $130 million market that more than doubled in the past year.

Jeffrey Hussey, F5's chairman, chief executive and president, says his company is building a three-tier traffic-management system that will help companies avoid traffic nightmares. F5, which was founded in 1996 and recently filed plans to go public, has built up an impressive customer list, including Microsoft Corp.'s electronic-commerce unit, Alaska Airlines and Internet-service providers such as At Home Corp. and PSINet Inc., which handled NASA's site for Sen. Glenn's flight.

Michael Mael, PSINet's vice president for applications and Web services, says conventional traffic management would have been ``too clunky'' to handle Sen. Glenn's flight. With F5, he says, ``we were able to take the data and pass itaround more efficiently.''

The core of F5's system is BIG/ip, a traffic-management appliance whose software assesses a Web site's server cluster and then efficiently distributes traffic to the site. Think traffic cop, with BIG/ip standing in the middle of the Internet intersection, spotting congestion, moving traffic around overloaded streets and getting everything to its intended destination.

F5 expanded BIG/ip's role early last year, adding a broader traffic manager called 3DNS to the system. Like BIG/ip, it directs traffic, but on a wider geographic scale. If an Internet service provider's servers are bottled up in Memphis, Tennessee, for example, 3DNS senses the tie-up and directs the traffic to another company server cluster in Portland, Oregon.

The third, and unique, leg of the system is global/Site, which will distribute evolving content -- like the progress of Sen. Glenn's flight -- in real time to all servers in the network at once. The company plans to begin shipping global/Site this summer.