Sally Floyd, a computer scientist whose work in the early 1990s on controlling congestion on the internet continues to play a vital role in its stability, died on Aug. 25 at her home in Berkeley, Calif. She was 69.
Her wife, Carole Leita, said the cause was metastatic gall bladder cancer.
Dr. Floyd was best known as one of the inventors of Random Early Detection, or RED, an algorithm widely used in the internet. Though not readily visible to internet users, it helps traffic on the network flow smoothly during periods of overload.
The internet consists of a series of linked routers. When computers communicate with one another through the internet, they divide the information they intend to exchange into packets of data, which are sent to the network in a sequence. A router examines each packet it receives, then sends it on to its intended destination. But when routers receive more packets than they can handle immediately, they queue those packets in a holding area called a buffer, which can increase the delay in transmitting data.
Moreover, the buffer has a limited capacity, so if the router continually receives traffic at a higher rate than it can forward, at some point it will discard incoming traffic.
For all their ingenuity, the creators of the internet did not foresee some of the difficulties that arose as the network grew.
“Before Sally, the working of network traffic mechanisms wasn’t completely understood,” said Eddie Kohler, a computer scientist at Harvard University and a longtime colleague of Dr. Floyd’s. “And as the internet expanded through the 1980s and began carrying much more traffic, that lack of understanding had real consequences.”
Well into the 1980s, the internet frequently experienced a period of huge degradation in performance known as a congestion collapse. Here the network’s capacity was consumed by computers repeatedly transmitting packets, which routers were forced to discard because of overload.
Dr. Floyd’s Random Early Detection was an enhancement of work done in the 1980s by Van Jacobson, a computer scientist whose scheme for signaling computers to slow down is often credited with saving the internet from collapse in the ’80s and ’90s. Dr. Floyd and Dr. Jacobson developed RED together.
“With RED, a router would generate a signal saying, ‘I’ve got enough backlog that I’m going to tell senders I’m backed up,’” said Vern Paxson, a computer scientist at the University of California, Berkeley, who collaborated on research with Dr. Floyd. This meant that by discarding the occasional data packet earlier, routers could often avoid getting completely clogged.
“The work required a lot of careful mathematics and the development of simulations,” said Dr. Paxson, whom Dr. Floyd mentored when he was a graduate student at Berkeley.
One byproduct of Dr. Floyd’s work reflected her passion for keeping things fair to all internet users. “Her work on congestion control was about keeping it working for everyone,” Dr. Kohler said. “For people with fast connections, and for people with slow connections.”
Since the paper describing RED was published in 1993, it has been cited in more than 9,100 articles. “That’s truly huge,” Dr. Paxson said, “up there with the most fundamental papers in computer networking.”
Sally Jean Floyd was born on May 20, 1950, in Charlottesville, Va. Her father, Edwin, was a mathematician at the University of Virginia; her mother, Marguerite (Stahl) Floyd, was an operating room nurse.
She spent a year at the University of Michigan, Ann Arbor, before transferring to the University of California, Berkeley, in 1969. She received a bachelor’s degree in sociology in 1971, with a minor in mathematics.
Seeking a way to support herself after college, Dr. Floyd took a two-year course in electronics at Merritt College, a community college in Oakland, Calif. In 1975 she became a computer systems engineer for Bay Area Rapid Transit, known as BART.
It was while working for BART that Dr. Floyd began to think about pursuing theoretical computer science, Ms. Leita, her wife, said. “She got curious,” she said. “The math genes she inherited kicked in.” Dr. Floyd’s brother, William, is a professor emeritus of mathematics at Virginia Tech.
Dr. Floyd returned to Berkeley in 1984 and received a master’s degree and then, in 1989, a Ph.D. there, both in computer science. With the rapidly growing internet seizing her interest, she joined the Network Research Group at Lawrence Berkeley National Laboratory in 1990.
In an interview for James Kurose and Keith Ross’s book “Computer Networking: A Top-Down Approach” (2000), Dr. Floyd said it was Dr. Jacobson who first got her interested in computer network algorithms in the 1980s.
“I hadn’t necessarily planned to stay in networking for years,” she said. “But for me, network research is more satisfying than theoretical computer science. I find I am happier in the applied world, where the consequences of my work are more tangible.”
In 1999 she joined the International Computer Science Institute, a research organization affiliated with UC Berkeley, as a research scientist. She retired in 2009 after receiving a diagnosis of multiple sclerosis.
Dr. Floyd met Ms. Leita, a reference librarian, in 1983. They married in 2013, soon after the United States Supreme Court cleared the way for same-sex marriage in California. In addition to Ms. Leita and her brother, Dr. Floyd is survived by a sister, Judith Floyd.
Dr. Floyd eschewed the limelight in her field.
“In the internet community, where arguments were often loud and long, Sally was the gentlest of souls,” said Deborah Estrin, a computer science professor at Cornell Tech in Manhattan. “Her response to comments that she disagreed with strongly was often a simple ‘huh,’ gently said and left hanging in the air.”
Dr. Floyd was also known for showing interest in the work of graduate students, whom she often met at technical conferences.
“Perhaps the most enduring scene is rounding some corner in a random hotel somewhere in the world and seeing Sally sitting on the floor chatting with a graduate student she’d met a few minutes beforehand about the student’s work,” Mark Allman, a longtime colleague, wrote in a recent online post. “That scene played out countless times.”
Source: Read Full Article