A court is blocking Microsoft from using a networking feature planned for the future operating system code-named Longhorn and a service pack for Windows Server 2003 that had been scheduled to come out last year, according to a company suing Microsoft over the technology.

The US District Court for the Northern District of California in San Francisco has granted Alacritec's request for a preliminary injunction to keep Microsoft from using the TCP (Transmission Control Protocol) offload technology that Microsoft has code-named "Chimney," Alacritech said in a statement Wednesday.

The technology was to have been included in the Scalable Networking Pack for Windows Server 2003, set for release in the second half of 2004, according to information on Microsoft's Web site.

TCP is the key protocol used in most IP (Internet Protocol) data networks. TCP offload technology shifts the burden of handling TCP tasks from the main processor of a server or workstation to a network interface card or other component, leaving the main processor more capacity for application processing. Alacritech promotes its patented SLIC Technology architecture as scalable enough to meet future networking and I/O needs at 10Gbps (bits per second) and beyond.

Chim-chimeny, cheroo

Alacritech claims it discussed its technology with Microsoft in 1998 and that Microsoft subsequently cut off communication with the company. In May 2003 Microsoft demonstrated a technology it called "Chimney" that Alacritech said was similar to its own intellectual property. Alacritech offered Microsoft a license, but Microsoft rejected Alacritech's terms, and in August 2004, Alacritech filed suit claiming patent infringement.

In November 2004 it filed a motion for a preliminary injunction to keep Microsoft from infringing the patent or inducing others to do so, according to Alacritech's statement.

Microsoft spokeswoman Stacy Drake said that Chimney was independently developed by Microsoft engineers. The company has just received the documents on the injunction and is reviewing its options, she said. Drake said the Scalable Networking Pack has not yet shipped, but did not know whether the lawsuit had stalled its release. She declined to comment on a possible licensing deal to resolve the dispute.

The preliminary injunction prevents Microsoft from "making, using, offering for sale, selling, importing or inducing others to use" Chimney, according to Alacritech's statement.

Alacritech, based in San Jose, California, makes network interface cards, iSCSI controllers and ASICs (application-specific integrated circuits) and sells products through both its own channels and other vendors.