On The Heavenly Slopes With ISDN

By Mike Lee  Several of Network Computing's editors spend their winter weekends skiing at Lake Tahoe. The skiing is among the best in the country, so it's well worth the travel time. If weather and traffic cooperate, it's only a 3-1/2 hour drive from our San Mateo, Calif., lab. If the snow is fresh, though, it's a long drive--up to eight hours--to the slopes. ISDN is a lot like our skiing experiences. Once you get there, you find that it was well worth the trip. But you may find the drive icy and your nerves will surely be rattled. Having suffered through the long journey to ISDN, we'd like to share our experiences with you, providing you with a few hints to help make your transition to ISDN a little easier. In addition, we compare our ISDN solutions to a less-expensive alternative--bonding of multiple analog connections. Getting to Heavenly If ISDN BRI service is available in your area, you're on the way. BRI service uses two channels for data/voice transfer (called "B," or bearer, channels and operating at 64 Kbps), and one channel for signaling (a "D," or data, channel at 16 Kbps). The two 64-Kbps B channels can be shared using Multilink PPP to create a single 128-Kbps connection. Along with the basic BRI service, ISDN packages typically ship with several call options, such as call waiting, call forwarding and caller ID. These are passed over the D channel. In our area, these options are bundled into a package called EZ-ISDN. You may have to order them a la carte, however, and there's no guarantee that your service provider will install them without your request. If you later decide to add or remove a service, you usually will be charged a change fee . Note that ISDN installation problems still are typical. Expect to spend several hours debugging and hanging on the phone with technical support. Take careful notes and keep good records throughout your installation process. Save all of the information you've obtained from the phone companies, including your SPIDs (service profile IDs), support phone numbers and equipment configuration information. This information will help you and your service provider debug unexpected problems. Depending upon the complexity of your home office, you may need only a terminal adapter--the ISDN equivalent of a POTS modem--or you may require a router. See our Network Design Manual on ISDN for information on which to choose and for more detailed information on ISDN technology and connectivity (www.NetworkComputing.com/netdesign/isdn.html). Lists of ISDN terminal adapters and small ISDN routers are also available in our Interactive Buyers Guide (buyersguide.nwc.com). Many providers offer complete ISDN packages, including hardware, installation and Internet access. If you don't have specific needs, this might be a reasonable solution for you. It will save you the trouble of dealing with two providers--one for ISDN access and one for Internet access. The Analog Way Analog bonding is an alternative to ISDN. Like ISDN bonding, analog solutions involve bonding two 56-Kbps modem connections using Multilink PPP. In either case, special hardware or software on both ends of the connection must be available to bond the two lines. Although this is common for ISDN, it may be difficult to find a service provider who carries an analog solution. To take advantage of 56-Kbps technology, one physical end of the connection must remain digital. Data flowing to the analog end can travel at speeds up to 56 Kbps, while data to the digital end can travel only at conventional modem speeds (28.8/33 Kbps).

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