As more companies pilot grid-based applications, the question for network executives is what effect grid computing will have on the design and performance of their infrastructures.

Initially, the answer appears to be none. That's because most companies are being driven to grid computing by a desire to increase utilization of their LANs and WANs. But long term, the trend toward distributed processing of compute-intensive and data-intensive applications might result in the need for more redundant network designs, smarter middleware and high-availability network services.

"Typically, you don't need to make significant modifications to your network infrastructure to make it work with grid computing," says Peter Jeffcock, group marketing manager for grid computing at Sun. "The primary change in adding a grid is in increased utilization and the number of systems connected."

But as network utilization rises, companies might need to upgrade bandwidth or storage, Jeffcock says.

"You may need to make some changes if your environment goes from running at 20% capacity to 80% capacity, because if you have a failure you'll start to lose significant functionality," he says. "You might need to rearchitect parts of the network around potential failure points."

Most companies testing grid applications today are trying to increase use of their existing networks, particularly 100M bit/sec or 1G bit/sec Ethernet LANs installed in the late 1990s. Many companies also have T-3 or higher WAN connections that were built for peak loads but experience significant excess capacity.

By distributing key applications across a LAN or WAN grid, network managers can increase the speed at which processing is done or the size of the data set that is processed without having to purchase additional hardware or software.

"Over the past 10 years, companies have spent an enormous amount of money buying networks and computers, and most of the time they are just space heaters," says Wade Hennessey, CTO and vice president of engineering at Kontiki, a video-transmission software company that recently introduced its first grid product. "Companies are not spending tons of money on hardware anymore. They're looking for something they can use with what they've already bought."

Most corporate grids run across intranets, while Internet-based grids are popular with the academic community. many companies are testing grids initially on LANs in a particular location and spreading them out across their WANs.

As companies gain more experience with grids, they are finding that they might need to redesign their networks or add new services. Mission-critical grid applications require some traffic engineering to ensure prioritization. Grid applications require higher availability and redundancy because they're distributed across a network.

"If you manage your own grid environment, you want high redundancy in your network, which can be fairly expensive across the globe," says Bernhard Borges, senior technologist with IBM Business Consulting Services. "You need to be very cognizant about the network. Rather than looking at it as a transport mechanism, you have to look at it as part of the operating environment. . . . With e-mail, you can apologize if something doesn't get sent. With a grid application, you can't afford to do that."