There were a lot of big numbers -- 6,800 miles between labs, US$1 million in donated equipment -- but a billion bits per second? New Macintosh PowerBooks already ship with Gigabit Ethernet connections. Indeed, the speed in question sounds far from earth-shattering. Why should onlookers feel awe?

The secret is, the breakthrough is not about speed. It is about solving tricky networking problems. Communicating smarter, not faster, was the goal. During those 58 seconds -- the time it took to transmit all 6.7 billion bytes -- the researchers made history.

Latency, King of Networking

Unfortunately, many headlines rushed to note that the raw speed of the transmission was 3,500 times that of a cable modem. This is not a big deal. Transmission at gigabit speeds over many miles has been a routine matter for Internet equipment vendors for some time. Fujitsu, a vendor of so-called "long haul" fiber-optic systems, sells products to phone companies that can send 3.52 trillion bits per second over a distance of 2,500 miles between repeaters, or 3,500 times the speed in SLAC's experiment.

In contrast, the Internet2 organization, which sponsored the most recent competition, set the bar for entrants fairly low. To qualify, competitors had to send no more than 100 megabits of data over no more than 100 kilometers between endpoints, Internet2's Greg Wood told NewsFactor.

SLAC's staff point out that the real issue was not speed but latency -- the smallest amount of time it takes for a packet of several bytes of data to travel from one end of the transmission to another. In this case, it took 170 milliseconds for a data packet to go from Sunnyvale to Amsterdam and back.

What's a Terabit Meter?

"The difficulties come with latency," Les Cottrell, assistant director of SLAC's Computer Services, told NewsFactor. To set up a transmission, the TCP networking protocol, which manages the process, has to send bits of what are called control data between the two parties. That means each computer is potentially stalled, waiting for the other to acknowledge receipt, before the next bunch of data can be sent. (continued...)

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