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The task force has defined several distance goals and has issued preliminary suggestions for minimum distances over various types of fiber. The task force identified five key distance pairings: two for multimode fiber and three for single-mode fiber (see "10 Gigabit Ethernet and OSI Model").

For the LAN, the task force has suggested that the 850-nm serial PMD should support a working distance of 65 meters on 500-MHzkm 50/125 micron multimode fiber. This type of fiber is not prevalent in today's installations. However, because of its low cost and ease of manufacturing, it may become the interface of choice for server connectivity at 10 Gbps.

The 1,310-nm WWDM interface should support at least 300 meters on 160 MHzkm 62.5/125 micron multimode fiber. It is important to note that this fiber (160 MHzkm 62.5/125 micron multimode) is the most common type of multimode fiber installed in the enterprise. It is also known as FDDI-grade fiber and is typical of fiber installed in the late '80s and early '90s. Depending on your fiber installations and how far you want to go, you may be able to leverage some of your existing fiber infrastructure when migrating to 10 Gigabit Ethernet.

For longer-haul campus, MAN and WAN applications, the task force recommends a 1,310-nm serial or WWDM interface that supports distances of at least 10 km over single-mode fiber, and a 1,550-nm serial interface that supports at least 40 km over single-mode fiber.

Because of all these physical interfaces, the task force has also introduced the possibility of media-independent interfaces, similar to the AUI interface of 10Base-T and the MII interface of 100Base-T. Several standards have been proposed: XGMII, XAUI and XSBI. While several standards for a universal interface have also been proposed, because of the sensitive electrical and timing issues involved with 10 Gigabit Ethernet, we most likely will never see a vendor-independent interface. Instead, each vendor will have a 10-gigabit media-independent interface proprietary to its solution (see "Fiber Types and Distances Supported").

The interfaces for 10 Gigabit Ethernet are fairly certain to remain solid at this stage of the game. The 10 Gigabit Ethernet task force's technical-change deadline was in May. Now that we have passed this landmark, the standard is virtually complete, and vendors can start building prestandard-compliant products. Only minor standard changes should occur after this date, changes that will not affect implementation but that might affect the final release date or potential interoperability of products.

Planning and PrepPing

Whether your interest in 10 Gigabit Ethernet is immediate or you're planning for down the road, you must address several concerns. If you are planning to retrofit a building or campus, your challenge lies in adapting your infrastructure to support the new data rates. FDDI-grade cabling will support a maximum distance of just 300 meters. For many campus environments, this means that multimode fiber will no longer be suitable for backbone networking. Single-mode LAN installations will be available for 10- to 40-km configurations, with the potential for 80 km or more as laser technology continues to improve. If your campus does not have sufficient single-mode fiber to replace existing multimode runs, upgrade now if you plan on running Gigabit Ethernet campuswide.

In developing new campuses and building construction, you must provision sufficient single-mode fiber to support the new requirements of 10 Gigabit Ethernet. Single-mode fiber was once an expensive option to multimode installations, but you should consider single mode not only for intrabuilding links but for vertical risers for future use.

Ten Gigabit Ethernet is expected to cost three to five times more than today's 1000Base-X interfaces when it becomes available. Early modules from Extreme Networks and Foundry Networks cost $40,000 or more, but a $10,000 to $15,000 initial price range is more likely by the time the standard is ratified in 2002. The good news is that many existing architectures, including Foundry's BigIron, Extreme's Black Diamond and Cisco's Catalyst 6500, will support 10-gigabit modules in their current form. Although these architectures were only marginally designed for 10 gigabit (many gigabit chassis architectures support 8 Gbps per slot, only 80 percent of the required bandwidth for a wire-speed interface), they nonetheless can leverage the technology to significantly improve data rates over 1-Gbps Ethernet, protecting your existing investment.

Ten Gigabit Ethernet will change the way enterprises use their networks. It will also change the face of MANs and WANs. With long-distance LAN PHYs and SONET-compatible WAN PHYs, Ethernet will take on a new role in the MAN. In fact, dark fiber metro applications--that is, running 10 Gigabit Ethernet over leased dark-fiber between campus buildings in metropolitan areas--will likely be first to use 10 gigabit, enabling high-speed connectivity across metro regions for a fraction of the cost of leased lines.

A former senior technology editor of Network Computing, Joel Conover is a senior analyst at tactical competitive response solutions firm Current Analysis. He provides rapid tactical analysis of industry events in the enterprise infrastructure market. Send your comments on this article to him at jec@currentanalysis.com.