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A: There is no panacea in the world of networking; each available technology has strengths and weaknesses. Satellite technology, for instance, is very capable of delivering high-bandwidth capacity over a geographically dispersed area. However, as anyone who has used satellite delivery knows, the technology has some drawbacks.

On the plus side, a satellite can typically deliver 20 percent to 30 percent savings over terrestrial technologies for delivering data to remote areas. Exact comparisons are not possible because carrier tariffs are specific to the delivery location.

Satellite is a Layer 1 technology that can transport IP and ATM, as well as other LAN frame types, such as 802.3. Typical uses of successful satellite technology include e-mail, User Datagram Protocol (UDP) broadcas t applications delivery, off-hours database replication and backups. At this time, satellite is not appropriate for all data communication because of the high latency that's incurred. The effects of latency on application performance vary depending on the upper layer protocols and applications in use. High latency can drastically affect protocols with built-in error correction, like TCP and X.25's LAP-B (see "Internet Rx," April 15, page 86). In that issue, we calculated the effects that a 12,000-mile round-trip from London to Los Angeles had on a line's maximum throughput. Using a Low Earth Orbit (LEO) satellite, round-trip distances exceed 40,000 miles, generating triple the latency of the terrestrial link to the same destination.

Although the sliding window mechanism employed by TCP can mitigate these effects, they still are significant. To minimize satellite latency effects, several satellite vendors are working on modifying TCP's behavio r. But don't hold your breath waiting for all hosts to support t hese new features.

Rain fade is another area of concern. You need to assess the frequency of thick cloud cover and storms (which can interfere with satellite transmissions) for locations you want to deliver service to.

With many Ka-band services coming online, the competition among satellite vendors will remain strong, with a continuation of competitive pricing policies. (Ku-band services offers the same service as Ka-band services, but operate at carrier frequencies higher up the spectrum.) Ka-band services use the 18-GHz to 31-GHz range of carrier frequencies, Ku band uses 11 GHz to 14 GHz, and C band uses 4 GHz to 6 GHz.