LAS VEGAS — At least five groups representing vastly different approaches to home networking preached interoperability at this week's Consumer Electronics Show (CES). But their message came amid demonstrations of diverse ways — over phone lines, airwaves and, in one or two cases, power lines — to interconnect home PCs and appliances.

Microsoft Corp. was the most visible, revealing an operating-system extension for home networks that would allow various devices on separate wired and wireless networks to link via Windows-based systems.

"We don't care what the transmission media is," said Phil Holden, home-network program manager. Microsoft proposes to extend the OS multilayer model to home networks (and, by implication, to insert itself as the network operating system of choice). With "Universal Plug-and-Play" (UPnP), all network devices would carry a small amount of ROM code (less than 40 kbytes) that would identify itself to a computer host. The host would automatically assign it an Internet Protocol address. Servers (Internet service providers on WANs, for example, or home PCs on LANs) would use something like a broadcast dynamic name service, said Holden, and home PC, palmtop or entertainment appliance clients would use something like a lightweight discovery protocol.

WinHEC target
"We plan to package the software technology up, making it available at the WinHEC in April for those who are interested in building their systems based on the Universal Plug and Play," said Craig Mundie, senior vice president, consumer strategy at Microsoft.

Microsoft's UPnP will compete with Sun Microsystems' Jini-like distributed-computing technology. Jini, based on Sun's Java language, is a separate scheme for connected devices across different networks and operating environments and will be detailed by Sun later this month.

The need to embrace diverse home networks was plain at CES. The HomeRF Consortium, which includes heavyweights like Hewlett-Packard and Intel, advocates wireless connectivity. The Home Phone Networking Association (HomePNA) advocates in-home phone-line wiring (with RJ-11 connectors) to network home computers. And startups like Enikia (Piscataway, N.J.) have shown networks that use home ac power lines to transmit data between computers and appliances.

Even among groups that advocate a similar medium, proponents back different technologies. Startup ShareWave (El Dorado Hills, Calif.), for example, took a "best-of-show" award for a wireless home network that offers high-bandwidth connections of up to 4 Mbits/second with video compression for home PCs and entertainment devices. ShareWave's marketing vice president, Bob Bennett, said he would reveal some technology in hopes of developing an interoperability standard.

Similarly, Jeff Thermond, president of Epigram (Sunnyvale, Calif.), discussed interoperability as he demonstrated his 10-Mbit/s phone line LAN. Epigram has offered HomePNA its system, which uses Ethernet protocols, as a model to copy for its own 10-Mbit/s standard. "HomePNA has a pretty aggressive schedule for developing the 2.0 spec," said Thermond.

But Bob Dillon, Enikia's outspoken vice president of marketing, put all the interoperability talk in a different perspective — characterizing it, perhaps, as "the emperor's new clothes." Enikia demonstrated a 10-Mbit/s LAN that uses ac power lines as its transmission media. It makes little pretense of being interoperable with Intellon Corp. (Ocala, Fla.), which offers 1 Mbit/s over existing power lines, or Adaptive Networks (Cambridge, Mass.), which uses power lines for 384-kbit/s control applications.

"Don't let the wire fool you," Dillon said. "The nature of the [transmission] problem changes with the data rate and the application. These systems are trying to do different things." The current "we-don't-compete" positioning among divergent home LAN exhibitors at CES is meant to communicate a unified message to the consumer, said Dillion. "The message is 'don't get confused, don't hold back, don't wait to buy.' "

-Additional reporting by Junko Yoshida