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Francis T. Nakamoto

Science Applications International Corp.

Honolulu, HI

Q: I received the following question from a colleague. Could you help?

We have plugged in a basic Ethernet local area network that Contingency Theater Automated Planning System, or CTAPS, runs on. I am told is that we are fighting a vendor-specific implementation problem between two equipment manufacturers, one using Fiber Backbone and the other Fiber Link. Also, our technicians tried to hook up a fiber-optic transceiver in every way and combination possible but always ran into the same problem.

Can you shed some light on what I think may be two fiber-optic Ethernet standards: 10Base-FL and 10Base-FB? What does each signify, and where can we get more information about them?

A: Your problem is not proprietary equipment. There are three types of segments included in the 10Base-F standard.

10Base-FL, the Fiber Link, is a full-duplex optical-fiber link segment. If you are using only 10Base-FL equipment, the maximum segment length is 2000 meters.

Mixing 10Base-FL and fiber-optic inter-repeater link, or FOIRL, equipment reduces the maximum to1000 meters. A 10Base-FL segment can be used between two computers, or two repeaters, or between a computer and a repeater. 10Base-FL is designed to interoperate with existing FOIRL-based equipment

10Base-FB, the Fiber Backbone, is a special synchronous signaling backbone used to interconnect 10Base-FB repeater hubs. This facilitates formation of large repeatered backbone systems. The maximum segment length between 10Base-FB repeater hubs is 2000 meters.

10Base-FP, the Fiber Passive system, is an unrepeatered optical-fiber mixing segment that links multiple computers via a 10Base-FP star coupler. The maximum 10Base-FP segment length is 500 meters.

For additional information, point your World Wide Web browser to http://wwwhost.ots.utexas.edu/ethernet/ethernet-home.html.