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Judy Estrin is what some might call a "serial entrepreneur."

Her current startup, Packet Design Inc., is actually her fourth.

When she left her position as chief technology officer at Cisco Systems to pursue Packet Design, the Israel native who now lives in Palo Alto said she knew it was "a controversial choice." But the former executive vice president of Bridge Communications, chief operating officer for Network Computing Devices and CEO of Precept Software — which was acquired by Cisco — felt it was something she had to do.

"I just love that startup phase," she revealed during a recent lecture, sponsored by the Jewish Community Federation's Business & Professionals Division at the San Francisco law office of Steefel Levitt & Weiss.

Named to Fortune magazine's 50 most powerful women in business three times, Estrin started Packet Design (as well as Bridge, NCD and Precept) with her husband, Bill Carrico. Founded in May, the Menlo Park-based company was set up to solve infrastructure problems within the Internet.

"Most people who use the Internet never look inside. They don't know anything about it; they just assume it works," she explained to the crowd of more than 50 business professionals, amid a sea of ringing cell phones.

"It's like a race car driver who just wants to drive," she said. "If he doesn't have the right engine, he isn't going to get anywhere."

Estrin, who sits on the boards of the Walt Disney Co., the Federal Express Corp. and Sun Microsystems (and "gets a lot of benefit out of all of them") likened this mentality to applying Band-Aids to a wound.

"The Internet industry uses a lot of short-term solutions," she said. "No one is really looking at the crack in the wall. They just paint over it."

Packet Design, on the other hand, wants to fix the crack in the wall by "developing IP technology that enhances the performance, scalability, provisioning and ease-of-use properties of the Internet." (IP refers to "Internet protocol," the type of numeric address the Internet needs to send the streams of packets that carry e-mail and other data between computers. Scalability refers to the ability to be made larger or smaller, and applies to the economic viability of a new product as well as its technical properties.)

The company is aimed at telecommunications carriers and enterprises, and will address problems brought about by "the sea of changes" in the Internet. One of these changes is optical networking, a newer method of data transfer that uses glass wires instead of metal wires. Another is the ability to access the Internet through mobile phones. A third is the vastly larger number of people now logging on.

"Some people think the Internet is done and ask me, 'What's the next big thing?'" she said. "Well, I answer, 'the Internet.'"

Fortunately, the Internet's growth spurt provides increasing opportunities for women, she added. Her No. 1 tip to the 50 percent female audience: "You need to know how to work with men, not how to be one.

"Women who are successful in business are women who are being themselves," she said. "I am who I am. I bring both strengths and weaknesses."

The primary obstacle for women, said Estrin, is finding the balance between work and family. The mother of a 10-year-old son said she does this by "juggling lots of balls, but deciding which ones are less important and which ones I absolutely cannot drop."

Estrin did, however, express concern with the small percentage of American woman actually studying engineering compared to higher percentages in other countries. To solve this she said, "We need to make sure girls understand what the fundamentals of education can bring you," namely, job opportunities.

But the problem in education, she said, isn't only limited to females. For this reason, Estrin suggested that Internet funders turn their attention and pocketbooks toward schools, kindergarten through grade 12 as well as college.

Estrin, who received a bachelor of science degree from UCLA and a master of science from Stanford, said many would-be entrepreneurs think they can start a dot-com without a good education to back it up.

"We have all these people expecting to become millionaires right out of school," said Estrin. "There's something broken with that philosophy.

"With the booming dot-com industry, people tend to think the educational process doesn't matter. But it does," she explained. "There's a big difference, for instance, between a computer programmer and a computer scientist. Sure we need both, but where would we be without the computer scientist?" (A computer programmer doesn't necessarily need a degree; a computer scientist does.)

By not putting funds toward education, Estrin said, we're "hurting ourselves as a society."