Volume 2. No 3 Information Technology News of the University of California, Davis Spring 1994

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ISDN
One Potential Solution for the Davis Comunity Network

by Russ Hobby, Technology Resources

[Editor's Note: Work continues on a prototype project to take advantage of ISDN technology in the development of the Davis Community Network. This effort is related to solving the intermittent difficulty people are experiencing with access to the campus modems, particularly those who wish to connect to the Internet. Here is an update on that effort from Russ Hobby, Director of Advanced Networked & Scientific Applications and acting Director of Technology Resources.]

I have been involved with the Davis City effort to create a community network form its beginning. Our main objective for the first two years was working with Pacific Bell to build the network on ISDN (Integrated Services Digital Network) technology. Things went quite well for a while, and it looked like Pac Bell was going to offer Internet services over ISDN to the home. However, when it came time for implementation, Pac Bell said that they could not offer Internet-type connections as part of their service. Since Internet connectivity was our real goal, our project was severely set back.

There were positive results from the work with Pac Bell, however. The Davis Pac Bell switch was upgraded to offer ISDN services in October 1993 - well ahead of the original schedule.

Let me explain how Internet connectivity differs from ISDN and how we hope to use the two together.

The Internet breaks a stream of information into "packets." Each packet has an address on the "envelope," and the network delivers the packet to the address. At the receiving end, the packets are gathered up, and the information stream is reassembled. Think of it as a series of letters that tell a story being sent through the US Mail. The advantage of the Internet is that you can use a single network connection to send to many locations at the same time, just as you can send letters to many locations with one mailbox. By the way, an information stream on the Internet can be one of many applications, such as electronic mail, remote login, video conferencing, and more.

ISDN can also be used for the same applications. However, ISDN follows the telephone model where you connect to one number at a time. If you want to exchange information with several locations, you call them up one at a time. Also, ISDN can only connect to other ISDN equipment. The Internet can run over many types of transmission media. For example, on campus we can use Ethernet, AppleTalk, modems, optic fiber, and more to connect to the Internet. And the person using the system does not have to worry what the other person is using. It all interoperates. The main advantage of ISDN right now is that it will work over the phone wires going to everyone's house and is an available service.

So, how do we use ISDN to get Internet connections? Our plan was to use ISDN to connect a home computer to an Internet hub. ISDN cannot connect to several locations at once, but the hub can. This way you can still create all the packets, each with an address, send them over ISDN to the hub, and the hub will deliver the packets to where they are supposed to go. Using the US Mail analogy, it would be like having a pneumatic tube to the post office. The tube only goes between your house and the post office, but the post office knows how to sort and deliver.

We were asking Pacific Bell to provide this hub as a service. They said that they could only sell the ISDN part. Though a third party could buy the ISDN, build the Internet part, and sell the combined services, that method would require two connections: one from the home to Pac Bell's central office and one from the Pac Bell office to the Internet hub. Requiring users to pay for two ISDN lines would bring the costs way up.

So what is a reasonable price? Our survey indicated that to hit the mass market, initial outlay for equipment would have to be less than $500 and the monthly rate would need to be between $20 and $30, with no usage fee. Since a modem uses a standard voice phone at a residential rate of about $12 per month and no usage fee, that approach did not seem cost-effective or marketable.

Though negotiations for an ISDN-based solution continue, the Davis Community Network has two other options under review: cable TV and wireless technologies. Efforts to bring the community online continue in these areas as well.