Software breaks data-transfer record

Software breaks data-transfer record If it detects many errors, the TCP deduces that the network is congested. It halves the sending rate, and begins edging back up towards the maximum.

This worked fine for the Internet of the late 1980s, when the TCP was invented. But it copes less well with powerful twenty-first-century networks. "The adaptation is too drastic," Low explains. "The speed jumps around from too high to too low."

It's like driving a car by flooring the accelerator for as long as you can, and then stamping on the brake when you hit traffic.

FAST talker

Caltech's alternative is called FAST, for Fast Active queue-management Scalable TCP. It detects congestion by measuring the delay between sending a packet of data and receiving an acknowledgement. As this delay increases, it eases off - just a little.

This deals with congestion before the error rate rises. "It allows you to adapt more smoothly," says Low. In tests using existing hardware and networks, FAST has run the international links between labs at more than 95% efficiency.