A User-Level

Note: the U-Net project has pretty much would-up. If you're interested in high-performance network interfaces, check out VIA and GigaNet. VIA is an industry standard which incorporates almost all the ideas of U-Net. GigaNet is a company that sells adapters and switches implementing VIA.

The U-Net architecture provides low-latency and high-bandwidth communication over commodity networks for workstations and PCs. It achieves this by virtualizing the network interface such that every application can send and receive messages without operating system intervention. With U-Net, the operating system is no longer involved with the sending and receiving of messages. This allows communication protocols to be implemented at user-level where they can be integrated tightly with the application. In particular, the large buffering and copying costs found in typical in-kernel networking stacks can be avoided and feed-back to the application about flow-control and packet loss is facilitated.

The key aspects of U-Net are:

  • U-Net defines a virtual network interface for commodity networking hardware and operating systems.
  • The U-Net virtual NI preserves the traditional protection boundaries between processes. Multiple applications can use U-Net at the same time without interfering.
  • U-Net uses commodity operating systems (Unix and Windows/NT) and commodity networks (Fast Ethernet and ATM).

U-Net is currently available on several platforms:

  • PCs running Windows/NT 4.0 and using a DECchip DC21140 based fast ethernet interface.
  • PCs running Linux and using a DECchip DC21140 based fast ethernet interface, a Myrinet interface, or using a Fore Systems PCA-200 (not PCA-200E) ATM interface.
  • Sparcstations 10&20 running SunOS 4.1.x or Solaris 2.x and using a FORE Systems SBA-200 (not SBA-200E) ATM interface.

Also check out the Intel/Microsoft/Compaq VI Architecture which is basically an evolution of U-Net.

Funding for the project is provided through a DARPA ITO contract (ONR contract N00014-92-J-1866). The initial versions of U-Net were developed under contract F30602-94-C-0224 from Rome Laboratory, Air Force Material Command.

P a p e r s

T a l k s

S o f t w a r e

P e o p l e

Thorsten von Eicken


Last updated: 11/25/96.

Page design 1996 by Angela Moll.
Artwork 1995 by Thorsten von Eicken.