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Breaking the Internet Speed Barrier
No matter where they live or what they do, Internet users have the same complaints. You can turn gray waiting for graphics-laden Web pages to display. Huge files download like mud. And forget about viewing animated or audio-enhanced Web sites or plowing through mountains of e-mail messages daily. Is there a high-speed fix? Sure--provided you can pinpoint the source of the bottleneck. Sometimes slow downloads and displays simply aren't under your control, but result from poor connectivity at the other end. Despite the high throughput satellite technology affords, it can speed Internet downloads only so much. During testing, for example, we reached a threshold when surfing certain sites: We were downloading data as fast as the host could deliver it, which in some cases wasn't very fast. There's not much you can do about that. If the bottleneck is at your end of the connection, however, you have several options. The least expensive solution is to upgrade your modem and find an Internet service provider (ISP) that offers 28.8-Kbps access. High-speed modems are a steal these days; so are ISPs, which are offering dial-in access for about twenty, and sometimes fifteen, dollars a month. AT&T, for example, now offers unlimited Internet dial-in access for $20 a month. But downloading files larger than 1MB over a 28.8-Kbps dial-in line can take nearly 15 minutes. Download that same file over ISDN, satellite, or leased lines, however, and it will take a minute or so. SURFING IN STYLEClearly, dial-in access is not the fix if you regularly download large files or if you want to surf in style without waiting for the pages to scroll by, .GIF by .GIF. What will do the trick? That depends. ISDN is your best bet today. It's the most mature and widely available high-speed technology. In fact, phone companies have been pushing ISDN for years, and now they have the motivation: a killer app and speed-starved users. ISDN offers decent pricing and performance compared with dial-in modems, delivering up to 128-Kbps throughput for about $150 per month, including the cost of the line and the ISP's access charges. (Of course, prices vary by phone company and ISP.) Hardware prices are falling, too: You can buy an ISDN modem for less than $400. ISDN also makes sense for corporations seeking inexpensive but speedy connections. And ISDN routers, which hook multiple users to an ISDN line, are (finally) getting easier to install and are more compatible with the ISDN switches at the phone companies' central offices. Broadband technologies, however, offer the best hope for moving lots of data quickly. Cable TV and satellite networks, for example, have bandwidth to spare but are hampered by the cost of upgrading them to support two-way communications. This is their biggest hurdle: Both were designed to deliver broadcast TV signals, making the transition to an interactive Internet access system expensive. Today, there's only one widely available satellite system, from Hughes Network Systems. It requires a dial-in line to transmit data at 28.8 Kbps, but it receives at around 200 Kbps--good for downloading huge files, but overkill for reading e-mail interactively. REINCAR-NET-EDCable TV is another one-way broadband technology looking to be reincarnated in the Internet religion. Here, the onus is on the cable system operators to upgrade their wiring plants to enable two-way communications. Cable modems come in all varieties, with uplink speeds from 99.6 Kbps to 10 Mbps and downlink speeds from 500 Kbps to 30 Mbps. While the technology is still in development, expect monthly prices of around $50 and low initial hardware costs. Narrowband networks, such as twisted copper wire, are more ubiquitous but have their own challenges, namely, upgrading to handle higher data throughputs. The most widely available narrowband technology today uses leased lines that can operate at speeds from 56 Kbps on up to multimegabit--but they're very expensive once you get beyond 56-Kbps connections. Also, the initial equipment layout can be several thousand dollars, and the monthly fees from several hundred to several thousand dollars (for the line and ISP charges). Last are such advanced digital technologies as Asymmetric Digital Subscriber Lines (ADSL) and Very-high-data-rate Digital Subscriber Lines (VDSL). Conceived for delivering video-on-demand and teleconferencing apps, ADSL is experiencing a renewed sense of purpose in Internet access. ADSL modems share some similarities with cable modems: They have different data transmission and reception rates, typically 16 to 500 Kbps on the uplink side and anywhere from 1.5 to 9 Mbps on the downlink side. Also, they require specially conditioned phone lines that can handle these higher speeds and the ADSL modems on either side of the line. A mere handful of customers are using ADSL in this fashion; the challenge is for phone companies to transform each central office into a routed Internet backbone. There are many different stakeholders here: phone companies, cable operators, and the traditional ISPs--and of course, you and I. Each technology promises to improve your access to the Internet--but each is not without its share of technical and logistical problems. Read on for the specifics of each setup, along with a look at a likely scenario for the future. While most of the attention surrounding Internet access has focused on the pipeline, in the future, it will be a commodity business. We've already seen AT&T offer free Internet access hours, and Pacific Bell also aims to get into the ISP business. Eventually, though, four or five dial-in players will dominate. Likely candidates include America Online, CompuServe, The Microsoft Network (and its principal dial-in access provider, UUNet Technologies), and perhaps one more entity drawn from the ranks of the phone companies. The second and more interesting battle, however, will involve content providers: those ISPs that don't offer any dial-in access of their own, but that provide a convenient, secure place to host Internet services, including Web sites, e-mail, and news. Others will tailor their offerings to small-business commerce. These two trends--pipeline consolidation and content proliferation--will fuel lots more traffic. And users will need higher-speed pipelines as they surf or migrate their own servers to content providers. All well and good, but which technologies will triumph? ISDN is the best bet in the next few years: The products are mature and it's widely available. The only cloud on ISDN's horizon is the phone companies, which are notoriously voice-centric. Earlier this year, for example, several phone companies raised their ISDN residential tariffs, complaining that home users were spending too much time on their ISDN lines! This is an opportunity cable companies can seize, but it won't be easy; making the one-way cable networks interactive requires a tremendous capital investment. The best efforts, such as the much-touted @Home venture, will require cable operators to think and act like ISPs. They'll have to build their own Internet backbones and route IP networks on top and alongside their existing networks. Also, the fractious debate over standards needs to be resolved quickly so vendors can produce equipment that works with more than one cable system. Leased lines are the toughest competition for the cable companies, and chances are prices will drop as phone companies devise new ways to cut their high profit margins in this area. Satellite technologies will evolve as a means to deliver bulk data transfers, but the software and hardware has to improve so that installing multiple IP configurations becomes easier. Although there is hope that ADSL and other higher-speed digital services will hit the market soon, the decade will likely end before these technologies make any significant inroads into Internet access. If you have an Internet connection already, check out Dan Kegel's ISDN Page, at alumni.caltech.edu/~dank/isdn/. It has lots of helpful advice, links to equipment vendors, and ISDN-ready ISPs. Another good place to look is the California ISDN User Group page, atwww.ciug.org/. While you may not live in California, this site has lots of helpful information about general ISDN usage, including the results of an interoperability test on over a dozen different units. Some other Web links for tracking down ISPs:
* Internet Society's guide, www.isoc.org/~bgreene/nsp-index.html
* Benoit Lip's worldwide access list, www.best.be/iap.html
* Mecklermedia's list of Internet service providers, thelist.com
Each phone company has both Web and ordinary phone-based help available for ISDN, located at the following sites:
* Ameritech (800-832-6328), www.ameritech.com
* Bell South (800-428-4736), www.smlbiz.bellsouth.com/bssbi.html
* Nynex (800-438-4736), www.nynex.com
* Pacific Bell (800-472-4736), www.pacbell.com. Pacific Bell
also offers its own Internet access services. More information
can be found at www.pbi.net.
* Southwestern Bell (800-792-4736), www.sbc.com
* U S West (800-246-5226), www.uswest.com
ISDNIf you're unhappy getting your Internet fix at V.34 speeds, the most promising alternative is Integrated Services Digital Network, or ISDN. Instead of a modem moving bits between analog telephone lines and digital applications, ISDN is a digital solution from end to end. Rather than connecting to the Internet at 28.8 Kbps, you can reach speeds of 56 to 128 Kbps, depending on where you live, where your Internet service provider (ISP) is located, and what equipment lies in between. This extra bandwidth is useful for everything from downloading files to browsing graphics- and multimedia-rich Web pages. If you need to download and upload data, then ISDN offers the best connection speed; alternatives such as satellite or cable links are currently one-way technologies that either require a separate dial-in line for uploads (satellite) or don't traditionally handle them at all (cable). If you frequently connect to the Internet but don't like waiting for data modems to negotiate the call, then you'll like ISDN's almost instantaneous connection: Being completely digital, it takes only seconds. In fact, of all the high-speed Internet access methods, ISDN is furthest along in its deployment, availability, and products. ISDN isn't for everyone or every Internet service, though. If you spend most of your time browsing newsgroups and reading e-mail messages, for example, you won't see much of a performance gain. Unless you're a speed reader, a V.34 dial-in connection is still your best option. ISDN also is expensive to install. Once that's done, you pay a small premium over ordinary analog calls. Expect to spend about $300 for the installation by both your phone company and ISP for an ISDN adapter. Equipment starts at roughly $400; and it can cost from $50 to $300 per month for the phone company and Internet access charges. These are just estimates, of course; you'll need to do research to find out which end of the cost spectrum you'll end up on. If you need speed, though, ISDN delivers. On our tests, for example, ISDN proved 2.5 times faster than a 28.8-Kbps analog phone connection when downloading a 485K zipped file: It took 4 minutes 2 seconds over the V.34 connection and only 1 minute 30 seconds over our ISDN line. We got similar results when displaying a graphics-intensive Web site (www.matrox.com). ISDN was 47% faster than the V.34 dial-in line: It took 34 seconds to display this site using a V.34 connection but only 18 seconds over an ISDN line. On both tests, we used 90-MHz Pentium systems connected to an ISDN line using an Ascend Pipeline 50 router. One caveat, though: An ISDN line to your ISP won't speed Internet access much if your provider is oversaturated--that is, if the line's always busy or you just can't get a response. If this is the case, ISDN offers little benefit over a standard 28.8-Kbps analog phone connection. ISDN BASICSThe notion behind ISDN is simple: It's a standard, two-wire phone line that carries three separate digital signals. This is called 2B+D in phone company parlance; it's also known as Basic Rate Interface, or BRI. Your phone company uses one of these channels (the "D" or delta channel) to handle control and signaling information, such as identifying the calling party's phone number and the amount of bandwidth the line occupies. The two remaining channels (the "B" or bearer channels) can carry voice, data, or both. B-channels can be either 56 Kbps or 64 Kbps apiece, depending on the equipment at your local phone company switch or central office. The two B-channels can also be bonded to act as a single 128-Kbps channel. (Bonding is an acronym for Bandwidth On Demand Interoperability Group.) Some ISDN equipment even supports dynamic bonding, which you use when you require the extra bandwidth--for downloading a large file, for example. With dynamic bonding, you pay for the connectivity only when you need it. Once you've downloaded the file, your ISDN router disconnects automatically, saving you the telephone connect charges. Another ISDN flavor is Primary Rate Interface, or PRI. This high-volume ISDN can handle either 23 or 30 bearer channels. It's often called 23B+D (used in the U.S.) or 30B+D (used in Europe and Japan) and can run at 1.544 megabits per second and 2.048 Mbps, respectively (over the B-channels). High-capacity PRI is most useful for connecting large networks or for ISPs linking their backbone networks, though. For small-office and home users, BRI is clearly the way to go. ISDN BLUESThough simple in theory, implementing ISDN is fraught with problems, starting with its uneven availability. While ISDN service is offered in most areas, it's not ubiquitous. Your neighborhood may not yet be served by a digital switch. Even if it is, the switch might not be compatible with ISDN. If it is compatible, the phone company's cabling to your home may be too long to support a digital transmission: ISDN works only when homes are less than 18,000 feet (3.5 miles) from a central office. Or your phone company may not be allowed to sell you ISDN service because the state's utilities commission hasn't yet approved that type of service. Even if your phone company offers ISDN service, not all ISPs offer ISDN access. And those ISPs that do provide it usually support only a limited variety of ISDN equipment. So before you buy any ISDN equipment whatsoever, make sure it will work with your ISP. ISDN is also a bear to set up. Unlike with an analog line, there's no dial tone, which makes determining if your line is working tricky. You also must configure many complex parameters for both your equipment and the phone company's central office, such as the switch type and whether the phone company is using 56-Kbps or 64-Kbps channels. In phone company parlance, this process is called provisioning. Though still difficult, provisioning was much harder until the phone companies standardized on a few preset configurations, including the National ISDN-1 configuration many ISDN routers use. You still can't unplug one ISDN router and connect another, although many ISDN equipment manufacturers are starting to support more provisioning configurations. NI-1 is still the most popular one, though. DATA: A FOUR-LETTER WORDBefore you can provision an ISDN line, you need to know the ISDN equipment you'll be using. Be prepared to spend hours talking to service representatives about central office switch types (Northern Telecom, AT&T), Service Profile Identifiers (SPIDs), and other arcane parameters. Why? Because phone companies still focus on delivering voice services. Although fax and modem communications consume an increasing share of the profit pie, many phone companies still think data is a four-letter word and haven't trained their service personnel on data communications. That is changing quickly, however, and you might get lucky. One user got ISDN installed in Bell Atlantic (one of the better local phone companies when it comes to ISDN) territory in northern Philadelphia. He could call around the country and get all the digital bandwidth he desired, with one exception: The local phone call to his ISP a few miles away wouldn't work. After many conversations with Bell Atlantic service reps, the problem surfaced: It was an incorrect entry in a routing table at the phone company's switch, and he was the first person to call that particular number. The snafu was easily fixed but not easily identified. This experience is by no means atypical. HARDWARE HURDLESIf you still want ISDN, then the first decision is which type of equipment to use: an ISDN modem, an adapter card, or a bridge/router. The equipment you choose depends on the number of computers requiring ISDN access: ISDN modems and ISDN adapter cards are for connecting single computers, while routers are for linking multiple systems to an ISDN line. Despite the name, ISDN modems neither modulate nor demodulate a signal. Instead, they terminate the phone company's ISDN line, stuffing the digital signal down the PC's serial port. These devices, which come in internal or external models, include different features. For example, models such as the U.S. Robotics Courier I-Modem integrate V.34 support, with analog ports for connecting fax machines and telephony devices. Many ISDN modems, however, lack ports to connect to analog devices. ISDN modems are perhaps the least expensive ISDN devices, and prices are dropping. For example, the popular BitSURFR from Motorola now costs under $400, as do rival products from such vendors as Diamond Multimedia Systems. (See "ISDN Gets Easier for Everybody," My Computer, May 1996, for a review of the Stellar Supra NetCommander ISDN.) Some phone companies are beginning to subsidize ISDN equipment and may offer even lower prices. The difference between an ISDN modem and an ISDN adapter is a trade-off between convenience and performance. Because ISDN modems connect to the PC via the serial port, they're limited to the port's speed. That's not a problem with newer computers, which have 115-Kbps serial ports, but it is in systems with older UARTs. Because ISDN adapters connect to the computer bus, they don't face this limitation. However, ISDN adapters are more difficult to set up than modems because they require familiarity with network drivers such as Novell's Open Data Link Interface (ODI) and Microsoft's Network Driver Interface Specification (NDIS). And ISDN cards are just beginning to support Windows NT and Windows 95. Popular models include Digi International's Digi PC IMAC and Gandalf Technologies' LANLine series. An ISDN bridge/router is the third option and the only choice for connecting multiple computers to an ISDN line. These external boxes connect on one side to the ISDN wall jack; the other side connects to an Ethernet network. Unlike an ISDN adapter, though, the router is a separate box with its own power supply and with both Ethernet and ISDN connectors. Some boxes also have ports for the control consoles used to configure them. The most popular routers are from Ascend, which offers the Pipeline 25 and 50 boxes. These typically cost from $900 to $1,300 each, with the higher-end model offering more filtering and network control options. Routers attach to a PC with a serial cable, or you can use telnet (which is basically a remote terminal session, but over an IP network instead of over a serial connection) to connect to them. With telnet, you can configure many different screens with various IP addressing information and network parameters, including how frequently you want the modem to dial into the Internet and whether it should do so on one or multiple B-channels. Newer products, such as Farallon Computing's Netopia, are easier to set up, but fewer ISPs support them. That's an important trade-off: Again, don't buy any ISDN equipment until you first check with your ISP to make sure that it supports that equipment. WHEN IN DOUBT, ROUTEMost ISDN consultants prefer routers, even for individual computer connections, because they provide room to grow. If you purchase a second computer later, you already have a network in place. And small LANs are relatively easy to administer. If you never plan on expanding and cost is a big factor, then stick with the ISDN modems; otherwise, consider routers. All three types of gear may come with an analog port so you can connect a standard telephone or fax machine to the ISDN line; otherwise, you can't use the ISDN line for anything other than data without purchasing an expensive digital telephone. Sometimes the analog port has nothing to do with the price: the Ascend Pipeline 25 comes with such a port, but the more expensive Pipeline 50 doesn't. After deciding which type of equipment is right for you--but before purchasing a unit--you'll need to find an Internet access provider that is an inexpensive (local) phone call away. (See the sidebar "Choosing an ISDN Service Provider.") DOUBLE THE PRICEWe've quoted various throughput numbers that range from 56 to 128 Kbps, which results from the myriad ISDN configurations and equipment. Some ISDN switches work only at 56 Kbps and not at 64 Kbps, depending on the software the central office switch runs. Often, older versions don't support 64-Kbps data connections. The 12% difference in performance between 56 Kbps and 64 Kbps is barely noticeable, though. Also, some ISPs can use only one of the two B-channels in the ISDN connection; others use both, but your equipment's setup may not be able to handle it. Ask your ISP what arrangement of gear will work--there is no other way to know ahead of time. Most ISPs that offer bonding also charge you twice as much for it: Double the data rate, and you double the price. There is work underway on a protocol, called Multilink PPP, to standardize the way two channels are used. But many vendors haven't yet implemented these standards. Again, before you get your expectations up about performance, check with your ISP and find out exactly the type of connection and configuration it supports. The ISDN situation is improving rapidly: Phone companies, flush with newly found deregulation religion, are now motivated to deal with data users. Some have even begun their own efforts as ISPs: Pacific Bell announced in February that it will offer its own Internet service in major California cities. AT&T has also begun to offer residential Internet access. Others have started to work more closely with system integrators. Nynex, for example, now outsources all of its order-taking and fulfillment of ISDN lines to a rotating series of integrators. This tends to improve service because customers get to deal with ISDN experts fluent in digital technology. ISDN products are also getting better, given that demand is reaching volumes predicted over a decade ago and end users are demanding less cryptic command-line interfaces. International usage also helps: Japan is almost completely digital, and so is most of Europe. Finally, there is lots of activity on the ISP front: More are opening up their networks to offer ISDN access, and those that already have it are expanding the number of areas in which they offer ISDN service. BRI A Basic Rate Interface is an ISDN service that provides up to two bearer (or B) channels of 64 Kbps each, plus one 9.6 Kbps delta (or D) channel for signaling and control. Individuals usually choose this type of ISDN service. ISDN adapter An internal card that connects the computer to the ISDN line. It runs at the speed of the system bus. ISDN modem An external or internal device that connects the computer's serial port with the ISDN line. It's limited to the speed of the serial port. Multilink PPP A standard way to automatically combine both ISDN B-channels into one 128-Kbps channel for faster transmission. Previously called bonding or bandwidth on demand. POP The point of presence is the physical site where an ISP has its modems and other networking gear. You dial into the POP for Internet access. PRI The Primary Rate Interface is a high-volume ISDN configuration with 23 or 30 digital channels. Each channel is 64 Kbps, for a total of 1.544 Mbps and 2.048 Mbps, respectively. Often used by ISPs to connect their network backbones. router A device that connects multiple network topologies, such as dial-in and Ethernet.
Step 1: Check availability. To find out if your local phone company offers ISDN, call the company or check with a local friend or business associate who already has it. You can also download Microsoft's ISDN Accelerator Pack from www.microsoft.com/ windows/ getisdn and use it to order ISDN service. One caveat: Some central offices support only 56-Kbps operations, while others can run at the full 64-Kbps speed. Step 2: Locate your local POP. Aside from hardware, the biggest ISDN expense is the cost of the call to your provider, so find an ISP with the closest ISDN point of presence (POP). This gets tricky because each ISP may offer ISDN at only a few of its POPs. When you get the phone number for the ISP's local POP, call the local phone company operator and ask what the charge is to call that number. Also, ask what the ISP charges for an ISDN connection, whether it offers two B-channels or one, and how it connects to the Internet; if the ISP has one 56-Kbps link to the Internet, look elsewhere. And if many users are sharing one T1 line, again, your ISDN connection won't be very satisfying. Step 3: Choose the hardware. Decide whether you want to connect one or many computers. ISPs offer differing levels of service and price points, so be clear about your needs. If you have multiple PCs, buy an ISDN bridge/router and make sure your network is set up properly for TCP/IP. Also, find out whether your ISDN device includes a built-in Network Termination 1 (NT1) unit, which powers the ISDN line. Newer routers and modems come with NT1 functionality, while older models require a separate box that can cost another $200. Step 4: Investigate the ISP. Check with your ISP to find out if it offers (1) ISDN to the POP nearest you; (2) individual or LAN service; (3) Internet access on both digital channels or on just one (with some ISPs, such as UUNet, unless you initiate the call on both channels all the time, you can't always get both); (4) the Internet services you need (such as dial-in access when you're on the road and can't use the ISDN connection); and (5) the ISDN equipment support you need--this is critical. Some ISPs will even sell you a router or a modem or configure equipment you've purchased. It's not a bad idea to take them up on either of these arrangements. Step 5: Order ISDN service. Call the phone company and order ISDN service, then buy your ISDN equipment (if you don't get it from your ISP). If your ISP is smart, it'll tell you the secret handshakes and 15 important parameters you need to get your line "provisioned." If not, go back to step 2 and pick another provider. Step 6: Sit back and wait. If you're lucky, the ISP might manage the whole installation process (including the phone company side) for you. If you live in Nynex territory, it offers a consultant who fills your order, which is helpful because you'll be dealing directly with an ISDN expert. Ascend Pipeline 25 and 50
Diamond Supra NetCommander ISDN
Digi PC IMAC
Farallon Computing Netopia ISDN Modem
Gandalf XpressConnect LANLine
Motorola BitSURFR Pro
Leased LinesIf you need continuous, high-speed Internet access but aren't willing to pay several thousand dollars a month for it, then you're reading the wrong section--move back to ISDN or on to satellite links. But if you have the budget and want all the possible bandwidth, all the time, then consider using a leased line to access the Internet; this technology offers the highest quality and the fastest connection. And if your company leases lines for voice calls among branch offices, you may already have most of the infrastructure you need to make that connection. You'll just need to purchase a separate line to run between your headquarters and a local ISP. Leased lines are dedicated, 24-hour-a-day circuits that the phone company runs directly from your door to your ISP's point of presence (POP); you can use them to send voice or data between two points. There are several flavors of leased lines, and they handle data rates from 56 Kbps up to 45 Mbps. Often, leased lines consist of fiber-optic cabling, though they can be copper if the distance between you and the ISP's POP is under (roughly) 3.5 miles. If you want to run Web and mail servers that outsiders can access, have a large network with dozens of active Internet users, or upload and download multimegabyte files frequently, leased lines may be the most cost-effective Internet access solution for you. Unlike with ISDN, your connection is active full-time--perfect for delivering surfers to your Web site. Unlike with satellites and cable modems, you get the same bandwidth in both directions. One of the advantages of leased lines is that you don't have to install anything other than the TCP/IP protocols and Internet applications on each desktop. As far as each client computer is concerned, the Internet is a local-area resource. Once connected via a leased line, you don't have to worry about "dialing" into the Internet; it becomes a natural extension of the local-area network. Where do you buy leased lines? Typically, your choices are limited. The local phone company is pretty much the only game in town, although AT&T, Sprint, and MCI are other options, particularly if you need to go longer distances. HOP ON POPTo establish a leased line connection to your ISP's point of presence, you'll need several pieces of gear, including a Data Service Unit/Channel Service Unit (DSU/CSU) and a router. These terminate the line and also provide signaling for the phone company. Phone companies often refer to leased lines as digital data service (DDS). You can connect a single computer to a leased line, although you'll probably still want to make use of an Ethernet connection from the PC to a combined router and DSU/CSU; this is a typical low-end configuration. Before you buy any equipment, however, find out if your ISP offers leased line services at the POP nearest your home or office. Because when it comes to leased lines, at whatever speed, you pay by the mile for the line the phone company runs between the two points. This can be costly even for a few miles of line, especially if you're in a rural area or if there's no spare capacity in your building (if it's a large building complex, for example). Whenever phone company installers have to be on the premises, pulling wire from the street into your building, it will cost you. There are other cost variables, including your ISP's pricing structure. Some ISPs have limited offerings of just a few different data rates, while others have more flexible plans. The price depends on the type of phone service you want. Obviously, the higher the data rate, the more expensive the line will be to rent from the phone company. A good rule of thumb: Figure on about a thousand dollars a month for short distances within major urban areas, with higher costs for longer lines in rural or suburban areas. Of course, if you have an ISP in your own backyard, leased lines could be relatively cost-effective, especially if you need full-time connections. LEASED LINE FLAVORSHow do you sort through these variables? First, decide how much bandwidth you can afford. The least expensive lines run a service called Switched 56 from the phone company. Because these 56-Kbps digital data lines are switched, they can connect to various endpoints or to network topologies. You pay only for the data packets you send and receive or by usage (e.g., monthly or hourly rates). Frame-relay service is a popular alternative to Switched 56 that delivers from 56- to 512-Kbps bandwidth. It's a packet-switching service designed to serve multiple locations, and it lets you purchase bandwidth when you need it. To understand frame relay, think of many users connecting to a shared virtual pool of connections, in which everyone's packets are individually labeled and mixed, then sorted out for their destinations. This is a very different technology than T1 service: You don't have a dedicated route from point A to point B. The route between the two points is never really known and changes from moment to moment. Frame relay can be very cost-effective in situations in which you don't need a continuous connection but still want a fast link when you do need it. However, ISPs that offer frame-relay access are still relatively rare, although this could become a growing field and compete with ISDN in the under-$250-per-month category for 56-Kbps links to the Internet. A few ISPs in California offer this type of connection, but you'll still need to purchase a leased line from your home or office to the local POP. Fractional T1 service is an alternative to Switched 56 and frame relay. As the name implies, you buy a fraction or a fixed number of 64-Kbps T1 channels. Some phone companies and ISPs offer this service and will sell you increments of a full T1 line (e.g., half or even an eighth) at proportionally cheaper rates. You don't share the line with anyone else; you just use it at slower than its maximum rate, typically for cost-saving reasons. Unlike with frame-relay services, for which you pay for the lines only when you use them, with fractional T1 service, you pay a fixed monthly rate because the line is up and running constantly. TOP OF THE LINEAt the top of the heap are the most expensive services: T1 and T3 lines, which run at 1.544 Mbps and 45 Mbps, respectively. A T1 line is made up of 24 separate channels, each of which can transmit data at a rate of 64 Kbps; there's another 8-Kbps channel for signaling and control, which lets you identify the calling party's number and track the amount of bandwidth a line is using, among other things. In most parts of the country, the cost of 8 to 12 slower lines (either Switched 56 or frame relay) equals the cost of a full T1 line. For example, if a Switched 56 line costs $100 per month, a full T1 connection would run $1,200 per month. If you have large-scale data-transmission needs--say, videoconferencing over the Internet--a T1 line might be more effective than multiple separate Switched 56 lines. Not every ISP offers these advanced digital connections, though. Two that do are PSI and UUNet, but there are others, which you can find by searching on "T1" through Yahoo! or AltaVista, with more regional offerings. Indeed, many super-ISPs use leased lines to provide wholesale Internet service to other, smaller ISPs down the line. In other words, the larger guys often rent a fraction of their leased lines to other ISPs. As with ISDN, pricing varies. For example, Global Access (www.blue-hwy.net/rates.html) charges $1,000 (for 56-64 Kbps) or $2,500 (for T1 service) to set up a leased line account, with monthly charges ranging from $300 on up to $1,000, depending on the throughput you request. This doesn't include the costs for the DSU/CSUs, routers, or other computers at your end of the connection, which can run from $1,500 on up, depending on line speeds and how many networks and nodes you need to connect. AU PAIRSOnce you've found a local POP that supports leased lines, you'll need to purchase a DSU/CSU. Actually, they come in pairs: One unit terminates the digital line at your office or home, the other terminates the line at your ISP. Kentrox, Adtran, and Bat make popular models. Phone companies also use the DSU/CSU to diagnose the condition of the line, provide the correct power to the circuit, and perform other technical chores. Think of it as an equivalent to a high-speed modem, although it doesn't modulate or demodulate the signal because the circuit is already a digital connection. Without a DSU/CSU, the phone company would have no way of knowing whether a line problem was on its side of the line or yours; with it, this still may be an issue, but at least the company has the tools to diagnose the problem. DSU/CSUs typically have two ports. The unit takes the digital signal coming from the phone jack's four wires (two for transmitting, two for receiving) into a V.35 interface, which is a high-speed serial communications connection between the DSU/CSU and your own networking gear, typically a router. It is a huge interface plug, about an inch square. IBM originally developed it, though the plug is now a standard. Routers have similar plugs to accept the V.35 cable from the DSU/CSU. Your PC connects to the router via an Ethernet cable. On the other side of the router is your LAN. You choose a DSU/CSU according to the speed of the digital connection and the kind of digital circuit you're buying; the faster the circuit, the more expensive the DSU/CSU. For example, those that handle 56-Kbps circuits cost about $250, while those designed for T1 speeds run approximately $1,500. You generally don't have a great deal of choice here; you buy whatever brand the ISP is using, and in some cases, the ISP will sell you the unit as part of its service package. While both ends of the connection are not required to use the same brand, it is good practice to do so to make it easier to debug problems. There are some combination DSU/CSU and router devices, such as Imatek's OnRamp, which are useful for small networks because they're easier to configure than two separate devices. But for the most part, purchase separate DSU/CSUs and routers; they're more flexible and easier to manage. If you upgrade your line speed from 56 Kbps to 256 Kbps, for instance, replacing a DSU/CSU is a simple operation compared with replacing a combo unit. TOEING THE LINEAlthough leased lines are the fastest way to access the Internet, they're not among the most innovative technologies, especially compared with ISDN and cable modems. Leased lines have been around for years. What is changing, though, and fast, is the price of DSU/CSUs. Having the Internet as a high-speed communications medium has made for more of a market for this equipment, which used to be available only from telecommunications wholesalers. While you can't buy a DSU/CSU at your local computer superstore, they are becoming more available through readily ISPs. And as more users seek faster and more-continuous Internet access, leased line prices will drop, particularly as the telecommunications deregulation fever motivates cable companies to offer competitive service at cheaper rates. This has already begun in areas where cable companies are allowed to offer bypass service, meaning they can circumvent the local telephone companies and offer Internet access (or other wide-area networking). Local phone companies, too, will get into the Internet access game. Given that leased lines are one of the phone companies' more profitable businesses, expect it to be a hotly contested corner of the market in this new era of deregulation. DSU/CSU Data Service Unit/Channel Service Unit is a device that terminates the digital line at the customer premises; the phone company uses it to diagnose the line and other technical chores. DDS Digital data service is an umbrella term for digital connections available from the phone company, including Switched 56 and T1 and T3 lines. Switched 56 Often the least expensive high-speed digital service, it operates at 56 Kbps and is used for point-to-point connections. T1 A line made up of 24 separate channels of 64 Kbps each, plus one 8-Kbps channel for signaling and control. Its total bandwidth is 1.5 Mbps. T1 is used mainly for bulk connections, typically among ISPs. T3 A line equivalent to 30 T1 lines that provides an overall bandwidth of 45 Mbps. V.35 The interface digital data lines use to connect to computers and routers.
SatellitesIf your sneakers have good traction, you're not afraid of heights, and you can install a TV antenna, then you might be interested in mounting a satellite dish to receive the Internet. You'll also need patience, because satellites and the Internet are still a fairly new union. While vendors such as NII Norsat International have announced plans to offer Internet access via satellite, the only product shipping today is Hughes Network Systems' DirecPC. While vendors will install and mount dishes (for a fee), configuring and maintaining them takes patience and a tolerance for cutting-edge technology. And when all is said and installed, ISDN is probably still a better bet for individual users with access to ISDN service. That's because satellites don't deliver the throughput rates they promise, setup is a bear, and they don't do uploads: To transmit data to the Internet, you still need a separate dial-in account to an ISP. PROMISE VS. REALITYInterestingly enough, eliminating our dial-in connection in favor of a satellite link accentuated other Internet bottlenecks. Many sites have poor connectivity: Either they link to the Internet via slow-speed lines or are choked with so many users that effective throughput was on a par with ISDN lines. In fact, depending on traffic, the time of day, and the number of users accessing a site, your satellite link may not buy as much bandwidth as you'd expect. We saw marked improvements when viewing graphics-rich Web pages and downloading huge files--particularly when compared with dial-in 28.8-Kbps modems (in some cases, the download speed was more than ten times as fast). But sustained throughput was roughly equivalent to the 128 Kbps that the combined ISDN B-channels deliver. For example, it took the DirecPC satellite we tested 143 seconds to download a 2.6MB file, which translates into a rate of 182 Kbps. Over ISDN lines, we downloaded this same file in 183 seconds, or at a rate of 149 Kbps. The V.34 modem downloaded that same file at a rate of 13 Kbps, which took nearly half an hour! Subsequent downloads of different-size files never topped these numbers. While it is fast, the DirecPC satellite offers nowhere near the 400-Kbps speeds that Hughes claims. DISH IT OUTHughes charges $699 for the basic kit, which includes either a two-foot- or three-foot-wide dish, mounting hardware, an ISA adapter card, and manuals. You supply the modem, an analog phone line, and the RG-6 coaxial cabling that connects the dish to your computer (which should be less than 150 feet away). Why do you need the analog line and modem? The satellite dish is a nonpowered receiver: It can't transmit information back to the Internet. So every time you type at the keyboard, your modem needs to dial your ISP and send that information back to the Internet. The information you requested is then relayed via the satellite back to your computer. The monthly charges for this service vary from $15.95 to $39.95 per month, depending on the amount of data you download. Then add in the monthly dial-in access fees and telephone charges to your local ISP. This could range from $40 to $70 more per month, depending on where you live and the cost of the call to your ISP. The connection between the dish and the PC is straightforward. The coaxial cable connects directly to an ISA adapter card, which is set up like a network adapter card (with a few caveats, which we'll discuss in a moment). Although you can save $450 by installing the satellite yourself, we don't recommend it: Two professional installers spent most of the day getting our rig working. Part of the problem is the nature and physics of satellite dish receivers. Satellites orbit geosynchronously, which means they appear to be flying over a fixed spot on the equator. (In DirecPC's case, it's the Galaxy 4 satellite at 99 degrees longitude, which is somewhere in the southern sky for most of North America.) So to receive signals, you have to point the dish precisely at the piece of sky from which the satellite is broadcasting. SATELLITES & MASOCHISMDirecPC includes a Windows 3.1 program called Antenna Pointing to help align the dish in three-dimensional space. Alignment is a two-part process. First, you type in your city and the program tells you the latitude, longitude, and elevation the dish requires; you then climb to the roof and manipulate screws and bolts to align the dish accordingly. However, this alignment is crude at best; the fine-tuning is the real challenge. For this, you'll use the second component of the program, which provides audio and visual feedback on the strength of the signal the dish is receiving. Unfortunately, if you can't see your PC's screen or hear the beeps from the roof, this is cumbersome to pull off--even with two people. The problem is that moving the dish even a fraction of an inch means the difference between great reception and lousy reception. Alignment is easier with the dish mounted on the ground, but then it's more difficult to find a clear patch of sky. And if a large building or trees block your southern exposure, then you won't be able to use any satellite service. Once the dish is mounted, there are three major configuration issues to contend with. First is the software, which is obscure and quirky. Although it will run under Windows 95, Antenna Pointing is still based on shaky 16-bit NDIS drivers, and it crashed occasionally during testing. Second, you must configure two IP connections because your PC has two communications paths to the Internet: one for receiving information via the satellite and one for sending it back via a 14.4- or 28.8-Kbps modem and an analog phone line connection through your ISP. Think configuring a single IP address is a challenge? Maybe that ISDN installation doesn't sound so bad after all. To begin, you must configure various settings to handle the log on, via modem, to your ISP. If you already set this up using Trumpet or CompuServe's Winsock dialer, you'll have a slight head start because they, too, require you to specify such settings as IP subnet masks and gateway addresses. The parameters in Hughes' setup software aren't as clearly labeled, though. Be prepared to call the technical support line. Next, you enter a second series of IP parameters to handle the downlink information; this ensures that downloads are routed through the satellite's receiver rather than your analog phone line. Some of this information goes in the setup software, and some of it--including the driver name and adapter address--goes in the PROTOCOL.INI and CONFIG.SYS files for the satellite's adapter card. You also have to set up networking IP parameters (subnet masks and gateway addresses) and dial-in IP configurations (for phone numbers, log-on commands, and passwords) because the satellite connection requires both types of connections. Unfortunately, the adapter card is left over from the 16-bit Windows 3.x world; Hughes hasn't yet developed a 32-bit driver that supports Plug and Play for its adapter. We experienced the usual series of Windows GPFs and had to periodically reboot our test system, a Dell 486/50. But once we got it working, the satellite did deliver. Hughes' obscure manuals didn't help, though. They explain the concepts involved poorly and aren't specific in areas you're likely to need assistance with. For instance, the manuals spend lots of time discussing jumper settings on the adapter card but don't explain how to configure the TCP/IP parameters to work with different ISPs. The company was rewriting the manuals at press time, though, so some of these omissions may be fixed by now. We also had a tough time with some of the error messages, which included warnings that certain procedures "may result in personal injury or death if not strictly observed." Finally, to provide Internet access to more than one PC, you'll need to connect each one separately to the coaxial cable via coax splitters and buy separate adapter cards and modems, all of which can get expensive. MIND YOUR BUSINESSDespite the problems, which often occur with nascent technologies, Internet access through satellite communications could still be the wave of the future--for businesses. The ideal application for satellites would be multimedia broadcasts to remote offices. Here, the intense graphical nature of the data would ordinarily require lengthy downloads or expensive leased lines. But a satellite's speedy downlinks would make it more cost-effective than T1, particularly for dozens of locations requiring huge weekly, or daily, downloads. A furniture-delivery company could use satellites, for example, to deliver product photos to remote retailers. But for individual home usage, satellites aren't quite ready for prime-time viewing. gateway address The address of an IP router, which forwards data packets from your local network to another LAN. NDIS Network Driver Interface Specification is a Microsoft standard that lets software, such as protocols and NIC drivers, communicate with the network interface card. ODI Open Data Link Interface is Novell's standard for interfacing network software and hardware. PROTOCOL.INI The Windows file that contains configuration information for Microsoft's NDIS devices. All versions of Windows use it, including Win 95 and NT. subnet A physical network within an IP network. subnet mask The portion of a 32-bit quantity that identifies either a physical subnet or a logical network segment. A typical subnet mask looks like this: 255.255.255.0. Hughes DirecPC
Cable ModemsOne day you might be tuning into the Internet Channel on your PC. Of all the high-speed Internet access solutions, cable TV systems are probably the most talked about. That's partly because they leverage existing broadband cable TV networks and partly because they promise to deliver high-speed access at an affordable price. Internet access via cable won't be widespread for about five years, though. Although cable modems are available today from such vendors as Intel and Motorola, at press time, they were being used only in trials, not commercially. To reach the mainstream, cable operators face an uphill battle. Like phone companies offering ISDN service, cable operators must gain expertise in data communications if they're going to win, and keep, customers. And there are considerable technical hurdles: While satellites are only one-way devices, cable modems can work in both directions if cable operators make their one-way networks interactive. Once that's accomplished, the technology could offer the best price/performance combination of any Internet access method to date, delivering close to 10-Mbps speeds at less than $50 per month--about twice the cost/performance factor of ISDN access. MORE THAN MODEMSToday, making the cable-to-PC connection requires a cable modem to modulate and demodulate the cable signal into a stream of data. The similarity with analog modems ends there, however. Cable modems also incorporate a tuner (to separate the data signal from the rest of the broadcast stream); parts from network adapters, bridges, and routers (to connect to multiple computers); network-management software agents (so the cable company can control and monitor its operations); and encryption devices (so your data isn't intercepted or sent someplace else by mistake). Each cable modem has an Ethernet port that connects to the computer (or network) on one side and to the cable connection on the other. You install an Ethernet adapter in the PC, then connect it to the cable's Ethernet port via a standard RJ-45 connector; you configure the PC with standard TCP/IP software. As far as your PC is concerned, it's hooked directly to the Internet via an Ethernet cable. There are no phone numbers to dial and no limitations on serial-port throughput (as is the case with ISDN modems). What you do get is lots of speed: Downlinks vary from 500 Kbps to 30 Mbps, while uplinks can, potentially, range from 96 Kbps to 10 Mbps. SUFFER THY NEIGHBORCan Internet access coexist with TV reception? Absolutely, that's the point. But pulling this off will require careful integration because of the way cable systems are currently set up. In each community, cable operators install a head end that receives both satellite and broadcast TV signals. Coaxial cable carries these signals to each subscriber's home. Depending on the number of homes and the distance between them, the operator may need to install amplifiers and filters to maintain signal strength. Typical cable systems serve between 500 to 2,500 homes on one line. Because the cable is broadband, it carries multiple signals, or channels. Most of these channels are devoted to TV programs, although many cable operators also carry radio stations. A TV channel occupies 6 MHz of the spectrum, and sometimes cable operators multiplex several channels into one. If the cable system were used strictly for data, it could deliver gigabytes of that data per second over hundreds of individual networks, with Ethernet-equivalent throughput. But TV signals consume most of the potential bandwidth. And most cable systems send these signals in one direction only: from the head end to your home. Internet access, obviously, is two-way: Every mouse click, every command and keystroke must travel back "upstream." TWO-WAY STREETTo become interactive, cable operators must allocate spectrum on the cable for upstream signals so you can send data from the PC back to the Internet. Typically, the upstream signal is transmitted via a low-frequency band that hasn't previously carried a TV channel. Why? Mainly because these low frequencies are noisy: Ham and CB radios, household appliances, lights, and other devices generate interference, which must be filtered somewhere between the head end and the cable recipient. Another problem: All homes (or offices) connected to the cable drop share this one transmission channel. Downstream transmissions have to be broadcast over a separate channel. And as is the case with an Ethernet network, too many nodes competing for bandwidth slow network performance. If your neighbors do lots of downloads, your throughput will suffer unless the cable operator provides additional capacity or extra routers and channels. Cable operators will also have to modify their cable amplifiers to separate the upstream and downstream signals. In some regions, they'll end up replacing most amplifiers, putting fiber closer to each home. Finally, cable operators will have to set up a communitywide Internet point of presence (POP) to serve all the networks associated with a particular head end. This will require the cable companies to plan very carefully and to gain an enormous understanding of TCP/IP networking. They'll have to set up routers and servers at the head end and at strategic places around the cable system to manage Internet traffic. FLIES IN THE OINTMENTAs the real estate motto goes, the three most important things are location, location, location. Because if your home or office isn't yet wired for cable TV, or if your cable operator isn't planning to offer Internet access, you can't do much to change that--short of moving. Another location issue concerns your home appliances. What if your PC isn't near your TV or existing cable drops? The cable company will need to rewire your house and snake the cable to your computer room. Chances are high, however, that your computer is located near a telephone jack, which can be upgraded to ISDN. And ISDN service is available today. There are other flies in the cable ointment. For one thing, cable modems are still fairly new; many have only recently begun shipping. Each modem manufacturer uses a different data-transmission specification, so cable modems from different vendors are incompatible. Therefore, if you move to another city, you'll need a cable modem from the local cable operator. Standardization is underway, though. Last year, nine vendors announced that their future products will work together, and four (AT&T, Intel, Hewlett-Packard, and Hybrid Networks) were planning to publish a standard as we went to press. Several industry consortia, including CableLabs, the Video Electronics Association, and the Digital Audio-Visual Council, are working on other standardization efforts. CHIPS AHOYPC and chip vendors such as Motorola and Intel are vying for leadership in the cable modem field, too, because the potential unit sales could easily equal PC volume. Some vendors have only recently espoused the Internet. Earlier efforts were tied to the success of the interactive-TV market; when that market fizzled, vendors began looking elsewhere for two-way applications. One ray of hope is an Institute of Electrical and Electronic Engineers (IEEE) working group committee, 802.14, that's trying to define a common media-access control scheme for sending data over cable. The committee is presently selecting the best elements from among 17 different proposals and hopes to have its recommendations finished by year's end. Given their immaturity, cable modems are still expensive. Zenith's cable modems, for instance, cost roughly twice as much as typical ISDN modems. To keep costs down, vendors such as General Instrument have announced that later this year they'll manufacture an internal PC adapter that can directly connect to the cable system. Having this adapter will make it harder for cable companies to debug connectivity problems--a serious issue given that many cable companies don't have a reputation for high-quality customer service. For the time being, those of us who frequently upload data won't be happy with many of the cable modems available today, because they use a lower rate to transmit data than they do to receive it. Motorola's CyberSurfr modem, for example, transmits at 768 Kbps but receives at full 10-Mbps Ethernet speeds. (That's why the best use of cable today is for receiving large files, Net news, and e-mail messages, for example.) STRAND AND DELIVERCable companies certainly have their work cut out for them. First, they'll have to decide which protocol to use to arbitrate access to the upstream channel. Several alternatives are being considered, and CableLabs, the cable-TV industry's research arm, is working on standards covering several areas: the connection to the subscriber's PC, the consumer radio-frequency interface, the cable network connection to the home, the interface between the router and the cable head end, and the interface from the head end to the Internet, among others. That's a lot of electronics to standardize, particularly in an industry not known for standards. Expect a long, uphill battle. It could be years before the majority of cable operators adopt any--let alone all--of these standards. The second major issue is how digital data will be transmitted within the local cable plant. Fiber is clearly the answer here, but many cable TV systems still have lots of coaxial cable. Laying all this fiber will be expensive and time-consuming, and most cable operators will wait and see what others do. Finally, cable operators will need to decide what kind of equipment connecting to the Internet will require. Will the cable company need to add its own TCP/IP infrastructure? Probably. As more and more people use Internet services, cable companies will need a well-thought-out plan for routing Internet applications. Bottom line: The cable industry is in for an overhaul if it's going to deliver Internet services successfully. Cable modems aren't yet ready for prime time. Until they are, sit back and enjoy the show. cable amplifier A device cable operators use to boost the signal strength when the distance between or number of connections attenuates the signal so that it noticeably degrades. cable modem Internal PC device that receives cable signals. Cable modems do more than modulate the signal, though: They include pieces of routers and hubs, and they run network-management and diagnostic software. cable drop The segment of cable that typically runs from the street or a telephone pole into your home. Cable drops connect to the main cable line at places called taps. head end The head end connects the cable network with dishes that receive both satellite and traditional broadcast TV signals, and with cable modems linking to the Internet. The coaxial cable carries these signals to each subscriber's home. The cable company's head end carries both broadcast signals and data to subscribers' homes. To access the Internet via a cable, several pieces must be in place. At the head end, cable operators have to install traditional office networking gear, such as routers, to an Internet backbone. The cable modem picks up these signals, strips out the data, and translates them into an Ethernet network connection. Converters are the set-top boxes that display cable channels. For the most part, using cable to access the Internet is still in the pilot stage, with one exception: TCI's @Home, which should be offering commercial service by the time you read this. TCI is the nation's largest cable conglomerate, and @Home has spent some time figuring out what kind of gear it needs to truly optimize the cable network for Internet access. The project, which is underway in Sunnyvale, California, uses Motorola cable modems. Essentially, @Home replicates various Internet content, such as newsgroups and Web servers, on its local system. @Home is creating a series of regional data centers to supply this content to each head end; each data center connects via @Home's own private backbone, which in turn has multiple high-speed connections to the Internet. This could be a content-control play, or it could be something that really improves performance and throughput--it's still far too early to tell. Other trials are also underway. Time Warner is conducting a 500-home trial in Elmira, New York, and will eventually connect schools, libraries, and government offices, too. The Elmira trial uses a 500-Kbps Zenith cable modem; a faster version, called Universal HomeWorks, will transmit and receive at 4 Mbps. Cablevision, too, is deploying these modems as part of a pilot project for the city of Fitchburg, Massachusetts. For details, check out a progress report from the city's planning coordinator, at www.iii.net/users/dstreb/inettalk.html. Other useful Web sites for information on cable modems and cable trials include Internet Access via Cable Modems, by the Howard University Distance Learning Lab, at www.coned.howard.edu/WebPages/ dll/CableModems/; Cable Modem Resources on the Web, by David Gingold, MIT Research Program on Communications Policy, at http://rpcp.mit.edu/~gingold/ cable/; Broadband Bob's Cable Modem Resource Guide, at www.tezcat.com/~chicago/modem1.html; and Sam's Cable Modem Trials, at www.teleport. com/~samc/cable5.html.
ADSLAsymmetric Digital Subscriber Line (ADSL) is the current darling of the phone companies for delivering advanced digital services. It offers the promise of high-speed transmissions yet allows the phone companies to use the copper wiring that already connects to each home. Someday, ADSL could be the darling of consumers as well: Because ADSL works over a pair of ordinary phone wires, you can use your existing analog phones and maintain a high-speed data connection at the same time. To do this, ADSL carries three separate frequency channels over the same line. The first set of frequencies carries plain old telephone system (POTS) conversations. Another series of frequencies transmits a 16- to 640-Kbps data signal (different products use different speeds) that carries information upstream from your home to the Internet. Like ISDN, this is a digital signal; but unlike ISDN, each channel goes in only one direction. The third signal is a high-speed downstream connection, which can run anywhere from T1 speeds, 1.5 Mbps, on up to 9 Mbps. The assumption here, of course, is that most of us will be downloading more from the Internet than we'll be transmitting to it. This is a huge gamble, one that cable and satellite vendors are also betting on. The difference is that satellite and cable technologies are much further along. One point in cable's favor is that there are many more cable modem vendors than ADSL modem vendors. To use ADSL--once it's commercially available--you'll need an external ADSL modem; there will also be one in the phone company's central office. While ADSL modems are still being developed, one prototype, from Aware, has three connectors on the back of the unit: One goes to the wall jack and then out to the phone company; one is for a standard RJ-11 phone jack for analog phone service; and one is an Ethernet twisted-pair RJ-45 connector that hooks the ADSL modem to your computer equipment. This means once you install an ADSL modem, you won't need special interface electronics to run your analog phones. That's a big plus, one that could speed ADSL's adoption as a single solution for home PC users and small businesses that don't want to install and pay for an extra data line. Also, most home PCs are located near phone wall jacks, which will make ADSL easier to install than, say, cable modems. PROGRESS REPORTWhile ADSL is attractive, theoretically, the marriage between the Internet and ADSL has not yet been consummated. Barely a year ago, ADSL was still viewed as a way for the phone company to deliver video movies and better compete with cable TV companies. And Ameritech, for example, has conducted field tests with Andersen Consulting to provide ADSL for distance learning in Michigan schools. Now, ADSL is newly incarnated as a means to high-speed Internet access, although companies are just starting to test the technology. Most ADSL Internet products are still on the drawing board, with only a few field trials comprising several dozen users. As an Internet pipeline, ADSL is too untested to count on. No ISPs have announced any ADSL service yet, making it even more difficult to make sweeping predictions. The first ADSL Internet field trial began this spring in Dallas. GTE is providing ADSL equipment to several central offices and 30 different sites, including linking to the Internet two public libraries, a bookstore, and some GTE employees. The company is testing two products from Aware and Westell Technologies; the Westell modems transmit data at 64 Kbps and receive it at 1.5 Mbps, while the Aware modems transmit at 500 Kbps and receive at 4 Mbps. These speeds are just the tip of the ADSL bandwidth iceberg, though. The ADSL Forum, an industry trade group, claims that speeds of up to 9 Mbps are possible and technologies that deliver these rates will be available this year. Another, similar technology, referred to as Very-high-data-rate Digital Subscriber Line (VDSL), promises even greater speeds. VDSL can operate at ultrafast rates, between 13 to 55 Mbps, but over about half the loop distances as ADSL. And VDSL and ADSL equipment aren't compatible, though they share many of the compression and modulation technologies to achieve such high throughput. GOING THE DISTANCETo get off the ground, ADSL must overcome a few potential problems. First, ADSL has a more limited range than ISDN. The faster the data rate, the shorter the distance must be between the subscriber and the central office. In some cases, to deliver the full 9-Mbps service, customers must be located less than 9,000 feet from their central office. This is still greater than the maximum distance traditional T1 lines allow (5,000 feet), but less than that for ISDN (18,000 feet). While most North American phone customers lie within this 9,000-foot range, many do not and will require expensive upgrades or repeaters to enable ADSL access. Another issue: Phone companies need to install ADSL equipment at both ends of the loop connecting the subscriber and the central office. Given the thousands of phone company central offices that will require upgrading, it is difficult to imagine this happening very quickly--look how long it took ISDN to catch on. To some extent, the same magnitude of upgrade is required for cable Internet access. And, like the cable companies, phone companies will have to become ISPs to provide Internet access. This means purchasing routers and switched hubs for each central office, along with high-speed lines that connect each central office to an Internet backbone. These ADSL upgrades are closer to what @Home--one of the first providers of Internet access via cable modems--is doing, but for cable TV systems rather than for the phone companies. However, given how little progress phone companies have made toward providing their own data service, this could be a significant hurdle to overcome. To make matters worse, as with any emerging computer communications standard, there are different (and incompatible) camps. There are two ADSL modulation schemes, or line codes: carrierless amplitude modulation (CAP) and discrete multitone (DMT). CAP is supported by AT&T/Paradyne and initially boasts speeds up to 1.5 Mbps. This scheme uses frequency modulation techniques that send a single signal down the wire; cable TV companies have been using these techniques for years. DMT is a newer scheme that divides the total bandwidth into 256 channels (of 4 KHz apiece) that can handle much faster speeds. The DMT equipment breaks the data signal into these smaller channels so that each channel carries a small amount of data; the overall stream is assembled at the subscriber's end. DMT products are just now coming out and will probably be more expensive than CAP products. But DMT has been endorsed by the American National Standards Institute. Still, there's no clear-cut winner, and it's too early to tell which standard will be more popular. If you expand your horizons to VDSL, there are two other modulation schemes besides DMT and CAP. Having multiple schemes is more of an issue for the equipment vendors than for users, though, because each phone company will decide which standard to deploy over its network. However, this multiplicity of choices will tend to keep prices higher because the phone companies will have to purchase and maintain different pieces of equipment to provide seamless connectivity with other phone systems. What will ADSL cost? There are no hard numbers, given the lack of commercial products. Early estimates peg ADSL modems at around $2,000 and up per line. But new chip sets should slash these prices to around $500, which is what cable modems currently cost. For ADSL Internet access to become popular and competitive with cable modems, however, modems will need to be well under $500. Remember: You don't pay for cable modems outright--you lease them from the cable company for a small monthly fee. It's not clear who will bear the cost for ADSL equipment. ADSL is also several years away from commercial service, while cable modems are entering into production now. Leased lines, which are available now and have been for years, are dropping in price, and greater numbers of ISPs are installing ISDN service. Although ADSL offers much promise, for the moment, it is still just that. David Strom has written several hundred articles on computer networking and the Internet and was founding editor-in-chief of Network Computing Magazine. He runs a consulting firm in Port Washington, New York, and publishes an electronic newsletter, Web Informant, at www.strom.com. ADSL Asymmetric Digital Subscriber Line is a catchall term for high-speed digital connections over two pairs of copper wire. Typically, ADSL downloads data faster than it uploads it. CAP Carrierless amplitude modulation is one ADSL modulation technique. Supported by AT&T/Paradyne, it handles speeds up to 1.5 Mbps. This scheme uses frequency modulation techniques for sending signals down the wire. DMT Discrete multitone is a newer--and faster--modulation technique than CAP that handles speeds up to 6 Mbps. POTS Plain old telephone system is what most residential customers have: a single analog phone line carried over two copper wires. VDSL Very-high-data-rate Digital Subscriber Line covers more advanced technologies that can deliver over 9 Mbps of data over copper wires. The appeal of Asymmetric Digital Subscriber Line (ADSL) is that it can provide high-speed transmissions over existing copper wiring. It will also let you use analog phones and maintain a high-speed data connection at the same time.
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