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Monday, August 9, 1999 Published at 17:17 GMT 18:17 UK


Sci/Tech

Gigabit per second delivered to desktop

The new software would make real-time, high-quality video routine

Computer scientists in the US have broken one gigabit per second data transfer to desktop computers in a local area network (LAN).

This is 20,000 times faster than communication through a telephone modem and was achieved using TCP/IP, the communications standard for the Internet.

Transferring a billion bits per second would mean, for example, that watching real-time high-quality video would be routine. However, one difficulty yet to be overcome is that the speed of writing to a computer's hard disk is still relatively slow. Server-based systems used by large businesses achieve about 40 megabytes per second while home computers write at four megabytes per second.

Rewriting the rules

Gigabit networks and network cards can be bought now but do not function at these speeds. However, by re-writing software, the team at Duke University, US, have shown these speeds are possible.


[ image: The increased data transfer speed will only benefit users if hardware keeps up]
The increased data transfer speed will only benefit users if hardware keeps up
"It's the first demonstration on public record of TCP/IP running faster than a gigabit per second, end-to-end, one network workstation to another," said one of the team, Jeff Chase, at Duke University.

"What we have done is provide the software support that's needed to allow others to achieve similar speeds on other networks that will arrive in the future," he added.

The backbones of current LANs can run at a gigabit per second but the data transfer to a desktop computer connected to the LAN is limited by the network card, usually 10 or 100 megabits per second.

Experimental stage

The Duke LAN is experimental and operates within a small space but Professor Chase believes the techniques developed there could eventually help computer users obtain more efficient access to larger scale networks, including a future version of the Internet.

It might also mean that standard TCP/IP type software could be used for such cutting edge applications as wiring together individual desktop computers into a massively parallel supercomputer.

"What we've done is narrow the gap between standard TCP/IP communications that everybody loves and knows how to use and has the software to use and these more cutting edge technologies that are harder to use and difficult for people to program," said Professor Chase.

"Over decades a lot of very smart people have done a lot of work trying to write the software that allows TCP communications at very high speeds. In some sense, what we have done really is show that they got it right." he added.

Streamlined software

The Duke team achieved speeds of 1.147 billion bits a second on a special high-speed Myrinet LAN with new Myrinet network cards.

They did this by streamlining the software operations which both the send and receive data. The modifications included:

  • "zero-copy data movement" which circumvents the time-consuming step of reading data from one area of computer network memory and writing it into another,
  • "scatter/gather input/output," allows data in various locations of computer memory to be rounded up and sent together as large messages.
  • "adaptive message pipelining," which schedules the movement of data between the network and an individual computer's memory to deliver high performance. The Duke group has filed for a patent for this,

By special agreement with Myricom, the group also made changes to the "firmware" codes in network cards that programmers ordinarily cannot alter.



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