Then theres 802.11 wireless networks, which are gaining ground among competing wireless technologiesincluding cellular communications. "If you put VOIP over wireless Ethernet, youre beginning to assault the cellular world. Today, there are dual-mode devicescell phones with 802.11. Competition will occur right there in your handset," said Metcalfe. Competition on the level playing field created by the string of IEEE standards for Ethernet is what has driven the technology to widespread adoption. But competition among multiple technologies in the wireless space is what will hold back more widespread adoption of wireless WANs, said John Yoon, senior director for product management at 3Com, in Salt Lake City. "Ethernet was well-understoodit was a very clear specification, and vendors could successfully manufacture and market [interoperable] products," Yoon said. "Because we didnt do an effective job in consolidating technologies in the wireless WAN space, [proliferation will be more difficult]. If it doesnt work out, its not because the technical problems couldnt be resolved but because the rollouts are expensive."Still, Ethernet is a likely successor to more costly Fibre Channel technology for SANs (storage area networks), as well as a replacement for proprietary, specialized networking technologies designed for cluster or grid computing.The Internet Engineering Task Force recently defined a specification, dubbed RDMA (remote direct memory addressing), which allows blocks of memory to be moved from one machine to another over 10G-bps Ethernet links. Already a dozen startups are creating network interface cards and chips that can support RDMA over Ethernet, according to Andy Bechtolsheim, vice president for the gigabit switching group at Cisco, in San Jose, Calif. "This will bring down the price of SANs to low-end markets. Everybody will be able to afford a SAN over Ethernet," Bechtolsheim predicted. HPs Clark said he envisions RDMA over 10G-bps Ethernet as the networking mechanism for grid computing. "It paves the way for allowing computers to be integrated into grids to aggregate the power of thousands of computers to work on problems that otherwise would take massive supercomputers," Clark said. Of course, application of the time-tested Ethernet technology into new areas, such as circuit-switched telephony, is governed by economics. Ethernet could even replace other, more expensive technologies. For example, Ethernet is beginning to replace leased lines in MANs because "you have less cost per bit for Ethernet than for T-1, T-3 or OC-12 kind of services," said Bechtolsheim. "It looks like SONET [Synchronous Optical Network] is doomed. Ethernet will take over the WAN access field," said Metcalfe. Although Ethernet today can use existing SONET rings for physical connectivity, many MANs use 10G-bps Ethernet over optical fiber connecting one switch to another because it is one-tenth the cost of SONET, said HPs Clark. "Those SONET rings are expensive and complicated to maintain. Theyll give way to Ethernet," he said. And the legacy modem for data communications over analog lines will eventually give way to alternate Ethernet-based technologies, according to 3Coms Yoon. "Broadband connectivity or wireless Ethernet or hospitality-based networking using Ethernet as the lingua franca will replace dial-up. But it will be years before people say, I dont need a modem," he said. The one LAN application that Ethernet has largely been shut out of is the direct, factory-floor networking of automated manufacturing devices. Ethernet, it was argued early on, is a nondeterministic protocol that cant guarantee specific response times required by robots and other timing-sensitive devices. But thats not the real reason it isnt in use there today, Metcalfe said, and that obstacle, too, is likely to come down. "The reason it isnt as dominant [in manufacturing] as elsewhere is because the factory floor is dominated by proprietary everything. Its a fragmented market, but [Ethernet] will come to dominate there," Metcalfe said. That will take place as the previous generation of factory automation devicesdesigned to transmit data in real timegives way to a new generation of such devices that "have a PC built into them that downloads the instructions for the machine to execute. Ethernet doesnt give you millisecond- accurate timing, but thats not needed now," said Ciscos Bechtolsheim. With all the changes that have been made to Ethernet over time, the only constant is its packet format. That is key because it is what has enabled products to interoperate, and it is what has allowed backward compatibility and forward compatibility as changes are made to the standard. "Thats what made it so successful," said Bechtolsheim. "The fact that Ethernet could maintain compatibility was a tremendous tribute to how long a simple design can last." Even with that constant, a variety of changes at Layers 1 and 2 over its 30-year history helped make Ethernet the most widely deployed networking technology there is. But in the next 10 years, changes to the Ethernet packets content will extend the technologys reach even further.