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ISDN On The Internet
Contrary to popular belief, ISDN (Integrated Services Digital Networking) is not new technology - in fact, it's about 20 years old. So why haven't you heard of it before? Well, until the WWW became so popular, there wasn't much you could do with an ISDN line - at least not much that would justify the expense. For years, telephone company and cabling and networking folks referred to ISDN as It Still Does Nothing - but not anymore!
ISDN is a digital telephone line. Unlike POTS (Plain Ole Telephone Service) lines, which carry analog (radio-wave type) signals, ISDN lines transmit voice and data in digital format. This means several things:
Until the explosive growth of the Internet in the last two to three years, ISDN was used only for particular high-speed data applications (like a graphics design company in this city who used an ISDN line to send the weekly national advertising layouts to the printer in a distant city). Now that everybody wants more pages faster, and delivered to more people in one location, ISDN has become popular for Internet connectivity - particularly network connections. What is required for an ISDN connection? First, the line itself. ISDN lines are sold in a package called a BRI (Basic Rate Interface). One BRI contains two B channels, each capable of carrying data at 64k, and one D channel used for signalling ("Hello, switch! We're coming through! This call is data only, heading to the main loop! Give us an open port!"). You can "bridge" the B channels to get a combined throughput of about 115k (you lose a little bit in the bridging). In our area, it costs around $100/month for unlimited local calling for a single BRI for business use, although the telephone company recently requested a change in the rates. Contact your phone company for pricing information in your area.Second, the line has to be connected to something. Ordinary telephones and ordinary modems do not work if you plug them into an ISDN jack - analog can't speak to digital. You must first bring the ISDN through a piece of hardware that converts the signal to something you can use. For the home office, for example, you can bring the BRI into a Motorola BitSurfer Pro (costs about $400), which allows you to connect one B channel directly to your PC (you will need a high-speed serial port) for Internet connectivity. The BitSurfer also has two regular analog phone jacks on the back, for using analog equipment on the digital B channels. For example, you can connect a phone to one B channel and use that as an ordinary voice line, and connect your fax machine or fax modem to the second line, and use it for faxing when it is not being used for Internet connectivity. Note: if you use one B channel for voice only, you should put the BitSurfer on a UPS (Uninterruptable Power Supply). POTS lines are powered through the switch, but an ISDN line converted to analog by your BitSurfer is powered by the Bitsurfer, so when the power goes down in your home, you'll have no voice line operable. For a regular business office, you can use an ISDN line to bring the Internet to all users on the LAN. A single B channel may be used by about 20 users on a LAN (assuming people get on and off the Net, not continual use). (Note: network connectivity to the Internet becomes economical at about ten users.) For a network connection, you need something a little different from the BitSurfer. I highly recommend the Ascend Pipeline series ISDN routers for network connectivity. These competitively-priced routers are powerful and reliable. You will bring the ISDN line into the router, which is connected to the hub on your LAN, and which enables every PC on the LAN to have full access to the Internet. Be careful, though! If you establish a network connection to the Internet, you need to install a firewall.
Compression is a consideration with the router, as well. For example, the Ascend routers use a proprietary compression system that increases your effective throughput as much as five times the normal speed of the line, if the Ascend routers are used at both ends of the dial-up connection. Choose your ISP and find out what hardware they are using before you purchase any yourself, so that you can take advantage of any compression benefits. Make certain, also, that the router you buy has a built-in NT1, as phone companies in this country do not usually provide that with the line hookup. Why use ISDN in the home office? If you spend very much time on the Internet, an ISDN line is a fairly economical way to accomplish all your telecommunications tasks. The two B channels allow you to use one for exclusive use as voice, and a second that can be shared for fax and Internet. ISDN lines can have all the normal special services (call waiting, call forwarding, voice mail, 3-way calling, etc.) programmed into them. The $100/month charge for unlimited use is reasonable for two lines, especially when one gives you much faster access to the Internet.Why use ISDN for network connectivity? Many ISPs offer ISDN connectivity in both a dial-on-demand and nailed-up connections. A dial-on-demand connection means that when a user on your LAN requests a webpage or tries to send email, the router dials up your ISP to complete the data transfer. In a nailed-up connection, the router and ISP dial up once and stay connected forever (or until the next big thunderstorm). ISPs may put several customers on a pool of ISDN lines with dial-on-demand connections, at a lesser price than a nailed-up connection. (In our area, an ISDN Net connection runs about $100/month for demand, $200/month for nailed-up. This is paid to your ISP for the bandwidth, and is separate from the telephone company's charge for the ISDN line itself.)ISDN offers some advantages over frame-relay connections. The hardware is usually a bit cheaper and installation costs are usually less, as well. ISDN also offers flexibility - because an ISDN line can dial anywhere, you can change ISPs by simply changing the phone number the router calls up (you will probably have to change your IP numbers too, unless you got them on your own). With a frame relay, you would have to pay installation costs all over again, and possibly termination costs on the old line, to change ISPs. Frame-relay lines are often mileage-sensitive (your physical location could greatly impact the monthly line charge), whereas ISDN lines usually are not. However, ISDN is not necessarily available everywhere, depending on the infrastructure of your switching station. Frame-relay lines can be installed anywhere, because they're custom - that's why they cost more. The primary drawback to ISDN is that no one is sure where it's going. A rate change to measured service could end the usefulness of ISDN for network connectivity for a halfway-serious business user. ISDN is still copper wire, which has an upper limit on transfer speeds. Who knows when fiber will be brought to the home and office? Exactly when are the cable television companies going to bring Internet access in, and how much will it cost? Like everything else in life, the future of ISDN is a big question mark. For the moment, however, it can be an economical solution to your Internet connectivity needs. Contact your ISP and local telephone company for specific pricing in your area. One final consideration: it's a bit trickier to set up an ISDN modem than an ordinary modem. If you choose to go with a BitSurfer or something similar, you may need professional assistance to install and set up the software to run it. Data communications is still a complex technology to deal with. In the home office situation, if you choose to use the ISDN for voice throughout the home, some additional wiring will be required. ISDN costs a little more in time, money, and effort, and may or may not be worth more to you. Talk to a local professional for some good advice on your particular situation.
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