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·LANart 10/100 Fiber NIC The LANart 10/100 Fiber NIC has two fiber optic interfaces: one for legacy 10-Mbps networks and one for 100BASE-FX connectivity. The solution is designed to failover to the 10-Mbps network if the 100-Mbps network should fail. LANart was unable to provide us with a product to review, but we felt its solution deserved merit--it is the only adapter on the market that supports both 10-Mbps fiber optics and 100-Mbps fiber optics. If you've got a network where 10-Mbps and 100-Mbps fiber segments coexist, the LANart solution might be for you. However, we speculate that the number of fiber links necessary to maintain two separate networks may make this product suitable only for niche applications.

Switch Resiliency Resiliency isn't limited to server-switch connections. A completely fault-tolerant design will include multiple links at every point. This can be achieved with Spanning Tree, but often the number of fibers on your campus is limited. When ban dwidth is at a premium, every fiber link counts. Many vendors have developed fault-tolerant solutions that allow active load-balancing across multiple resilient links. Here are some of the most prominent technologies we've tested.

·Cabletron SecureFast Networking Services Switches that support Cabletron's SecureFast VLAN code also support multiple active links between switches. Dubbed Virtual LAN Link State Protocol (VLSP), Cabletron's solution provides users with redundancy, load-balancing and quick recovery in the event of failure. Up to three links can be configured between each pair of switches. These links need not be over the same media. VLSP is proprietary, but gives users a wide range of options when it comes to building resilient networks. We tested Cabletron's MMAC Plus chassis and its VLSP capabilities in our first Layer 3 switch test last year (see "Network Layer Switching for the Corporate Intranet," at www.NetworkComputing.com/801/ 801r1.html). It was the best of the bunch.

·Cisco Fast EtherChannel Fast EtherChannel may land itself a seat in the standards chair if Cisco has its way. Cisco has submitted its channel technology to the IEEE standards committee and has more than 15 other vendors rowing toward the Cisco Fast EtherChannel shore. In a nutshell, Fast EtherChannel enables two Fast EtherChannel devices to be connected by up to four resilient, load-balancing connections. Newer Cisco switches have support for two or more ports of Fast EtherChannel, letting you build "fat pipe" networks today using Cisco's equipment (see diagram at left). Cisco also plans on moving its channel technology to Gigabit Ethernet sometime down the road. With a promise like that, Fast EtherChannel should definitely grab your attention.

·Performance Technologies Nebula 8000 If you absolutely can't afford to have a moment's downtime, look to this switch. The Nebula 8000 is a 32-port, nonblocking 10-Gbps 10/100 switch. But unlike any other product on the market, it features redundancy at the physical layer. The "ports" on the switch are connected to a dual mirrored switching fabric. In normal operation, each port has its own logic to handle all of the switching demands on that port. However, should something critical fail in the switch--a PHY (physical layer) controller, a RAM chip or any other part of the switch--you can remove half of the switch without losing connectivity.

Furthermore, it isn't necessary to play musical cables as you swap out the defective board. This innovative design lets you pull out the fabric and physical logic and replace it without a second of downtime. During the swap out, the PHY encoding and switching is handled by the resilient half of the switch. This will have an impact on network performance, but not network connectivity. When minutes mean millions, this is the switch that can answer your prayers.

Joel Conover can be reached at jconover@nwc.com.