II-F. Design of the Metropolitan Area Network

Baseline Connectivity. Baseline connectivity for the project was initially provided through dialup routers operating over standard (analog) telephone lines. This architecture was very inexpensive to implement, since local phone calls are untimed in our area and billed at the flat rate of seven cents per call. As expected, the use of graphical applications stressed the 14.4 kilobaud connectivity provided through this arrangement. The availability of school-based servers made this less of a problem than it might have been, but 14.4 kilobaud is clearly inadequate for the Internet connectivity of whole school sites.

Intermediate Bandwidth Options. We have carefully surveyed the options for expansion beyond our baseline low-bandwidth connectivity. The results of our studies are summarized in a paper [6] "Stages of Internet Connectivity for School Networking," which has begun to receive wide circulation. Specific examples of higher speed connectivity are currently being implemented in each of the four initial sites. All of the second-year sites will be provided with intermediate-bandwidth connectivity of at least 56 kilobaud. The methods being employed include Data over Voice, ISDN, LADS lines and "striped" multiple modems.