ernet service provider (ISP) access fees, and your telephone bill. As our tests clearly showed, however, full promised throughput is rarely, if ever, achieved.
The hype surrounding the 56-Kbps technology has engendered a number of myths and misconceptions. Although you must buy 56-Kbps modems (or upgrade existing ones), 56 Kbps doesn't require any changes to your phone lines. Vendors are quick to note that this is a significant advantage over ISDN. Unlike previous modem standards, however, 56-Kbps speeds aren't supported in peer-to-peer connections. High-speed transfer is a one-way street from service provider to user only.
Even if you choose 56-Kbp
s, you must still standardize on one of two incompatible proprietary specifications. U.S. Robotics, currently the largest modem maker, was the first to deliver its X2 56-Kbps modems. Rockwell Semiconductor Systems, on the other hand, is promoting its K56flex implementation of 56 Kbps.
Both the X2 and K56flex camps are jockeying for top position in the standards arena. Expect most vendors to offer upgrades to the eventual single standard -- many will do so for free.
The continued need for high-bandwidth connections has pushed ISDN modems nearly to commodity status. While modems are available, connections often aren't. Not nearly as universal as some claim, ISDN is generally available in most major markets.
Basic ISDN service provides two B-channels, each of which can carry 64 Kbps of data or a voice call. Combine the two channels, and you have 128 Kbps of bandwidth on tap -- two and a half times that of even an ideal 56-Kbps connection and four times that of a 33.6-Kbps V.34 modem.
ISD
N's all-digital nature allows it to provide connections that don't depend on the vagaries of the Public Switched Telephone Network (PSTN). Unfortunately, the need to provide a dedicated digital line is also ISDN's big disadvantage. Even if ISDN service is readily available at your home or office, the start-up fee, installation cost, monthly fee, and per-minute toll quickly mount, making ISDN an expensive solution for casual surfers.
One of the most intriguing and elusive data transfer technologies today is Digital Subscriber Line (DSL). Potentially, DSL makes a high-speed data channel available to anyone with a standard copper telephone line. The pervasiveness of plain old telephone service (POTS) makes DSL an attractive alternative to ISDN or cable modems. And with a DSL modem at both the phone company's central office and your location, you can receive data at speeds hundreds of times faster than the best ISDN line. Asymmetric DSL (ADSL) can provide a bandwidth from 608 Kbps to 8 Mbps to customers ove
r a single copper loop. Additionally, upstream (customer to network) data rates of 9.6 to 944 Kbps and telephone voice service can be supported simultaneously on the same loop. Although potential data rates decrease as the distance from the central office increases, some ADSL systems can also operate over distances of up to 18,000 feet or more. This lets ADSL service be offered to most existing telephone customers.
Defining the Field
We asked manufacturers of 56-Kbps, ISDN, and ADSL modems to
provide hardware
for this omnibus Lab Report. The 56-Kbps modem vendors responded with enthusiasm. Thirteen vendors submitted 18 modems -- eight based on X2 and 10 based on K56flex technology. Prices of the nine internal and nine external modems ranged from a low of $148 to a high of $275. Of all 56-Kbps vendors in our tests, only Practical Peripherals had offerings based on both standards.
The field for ISDN modems was considerably narrower. Seven vendors submitted modems for o
ur evaluation. Prices for these modems were attractive -- many undercut the more expensive 56-Kbps offerings. The bargain of the group sells for a mere $195, and the pricier units will set you back $399. There was no correlation between price and performance, although the most expensive unit also led in features and usability.
Rounding up ADSL modems proved to be the most challenging task of all. Although more than two dozen equipment makers claim to offer DSL products, only seven of them were able to produce modems for our review. Full production of these units may be as low as only thousands per quarter. For service providers preparing to commit to DSL service, this lack of boldness should serve as a warning to go slowly when choosing high-speed modems.
Pricing for ADSL is less than straightforward. Single-unit prices ranged from $995 to $10,000. But the more realistic 1000-unit pricing is generally between $500 and $1500 per line. You'll have to hammer out volume pricing with the vendor of your
choice.
Contributors
Andy Froning,
Managing Editor/NSTL
Dorothy Hudson,
Project Manager/NSTL
Maryanne Eves,
Acquisitions Editor/NSTL
Michelle Campanale,
Technical Editor/BYTE
Linda Higgins,
Editorial Associate/BYTE
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Bandwidth on a Budget: 34 Fast Modems
