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Sally Floyd, Who Helped Things Run Smoothly Online, Dies at 69

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Computer scientist Sally Floyd in an undated photo.

Floyd's work on congestion control, a colleague said, helped keep the Internet working for everyone.

Credit: Carole Leita

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."


From The New York Times
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