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The X (DSL) files; prepare for the invasion of DSL and its many alien mutations.

Despite their limited availability and lack of standards, digital subscriber line (DSL) services seem to have the edge over cable modems in the race to provide tomorrow's telecommuters with fast, reliable, and low-cost Internet access.

That edge, however, appears less clear now that AT&T and cable company Tele-Communications, Inc. (TCI) can pool their resources to provide high-speed Internet access via cable modem for a discounted package price--a price that also covers phone, long-distance, wireless, and cable-TV service. Suddenly, the pressure is on network vendors, regional Bell operating companies (RBOCs), and competitive local exchange carders (CLECs) to deploy DSL services as quickly as possible and to resolve interoperability and other issues that hinder user acceptance.

Currently, users must grapple with a confusing array of incompatible DSL offerings (see sidebar). Even within a service category, such as asynchronous DSL (ADSL), there's a lack of standards. Some products use a line modulation technique known as discrete multitone, while others use carrierless amplitude modulation. Clearing up the compatibility issue is important for users. They want to buy products today with the assurance they will be able to use them tomorrow, even if they choose a new service provider that uses hardware from a different vendor.

To unify the fractious DSL market, a group of vendors--including Microsoft, Intel, and Compaq--have thrown their support behind a standardized version known as Universal DSL (UDSL), or DSL.Lite. It is less expensive than ADSL and easier to install. ADSL service requires technicians to install splitters at the customer premise to separate voice and data traffic. UDSL service doesn't require a splitter and can be activated quickly and simply from a central office. The group's goal is to have a standard ratified by October, with UDSL products available in the fourth quarter. The intent is to make DSL.Lite a subset of ADSL so that ADSL modems would be able to function as DSL.Lite devices as well. Another standards effort seeks to let DSL modems reveal, during handshake, what DSL technologies they support so they can negotiate how best to communicate.


Another obstacle is the perception that RBOCs are dragging their feet with DSL for fear of losing revenue from ISDN, T1, and other high-speed services. To date, much of the impetus for deploying DSL service has come from CLECs such as startups Covad Communications Co. and NorthPoint Communications Inc. in San Francisco. These companies view DSL as a key enabling technology to support not only high-speed Internet access, but a wide range of IP services, including virtual private networking and voice, fax, video, and multicast broadcasting over IP.

Covad offers service speeds from 144 Kbps to 1.5 Mbps using ISDN-based and rate-adaptive DSL. To make service provisioning easier, it drops the separate voice channel that normally comes with DSL. Northpoint primarily wholesales DSL access to Internet service providers (ISPs) for resale to customers, though one user, Employers' Medical Network of San Jose, leases a symmetric 486-Kbps link directly for $250 a month as a cheaper alternative to T 1 service.

In the Midwest, DSL, Inc. of Waukesha, Wis., sells to users and to ISPs directly at prices ranging from $449 per month for 1.6-Mbps ADSL to $1,800 per month for 7-Mbps ADSL service. Meanwhile, in Florida, Supra Telecommunications & Information Systems, Inc. is launching a service in Miami, Ft. Lauderdale, and West Palm Beach using Paradyne's Hotwire rate-adaptive DSL equipment. Speeds will range from 2:90 Kbps to 2.90 Mbps, depending on line conditions and distance from the central office, with pricing starting at $60 a month.


In recent times, though, the RBOCs have become more aggressive, and all of them have now announced plans to offer DSL services. Pacific Bell, for instance, has accelerated its schedule for deploying DSL services to more than 200 California communities, prompted in part by the competing services already being offered in its market by Covad and NorthPoint.

PacBell's DSL services weren't expected until the fall, but now it says 65% of its 5 million business and residential customers will have high-speed local access by summer's end. For business users, the Office Pack offers a downstream rate of 1.5 Mbps from network to user and an upstream rate of 384 Kbps for $189 per month. Service is also available for $99 a month for 384 Kbps in both directions. There's also a one-time installation charge of $125, and customers must be within 16,000 feet of a telephone central office.

In one of the more ambitious moves, US West Communications is targeting 40 cities initially with its MegaBit Services ADSL offering, which is based on Cisco Systems' SpeedRunner modems connecting to a user's PC and traditional phone jack. With speeds up to 7 Mbps, the service includes an "always-on" data channel and a voice circuit for making and receiving calls. Included in the offering is a service called MegaOffice, aimed at telecommuters and small businesses with 512-Kbps access for about $65 per month. For heavier Internet users, the MegaBusiness service provides 768Kbps access for about $80 per month. MegaBit service offers 1 - to 7-Mbps access for $120 to $840 per month.

US West is speeding the provisioning of its DSL services by using NetProvision Activator software from Syndesis, Ltd. of Richmond Hill, Ontario. With the software, a technician can provision the hardware needed to set up a DSL circuit from a single management platform, reportedly cutting the time needed from hours to seconds.

GTE Network Services also has an aggressive plan to roll out DSL services in 16 states, including ADSL and symmetric DSL packages ranging in speed from 256 Kbps to 1.5 Mbps downstream and from 64 to 768 Kbps upstream. Prices run from $30 to $250 per month, plus a onetime installation charge of $60 to $140 and a modem lease of about $12 a month. Through an arrangement with GTE Internetworking, a subsidiary and ISP in Cambridge, Mass., customers have the option of bundling the service with Internet access for about $60 per month. For its service, GTE says it will use equipment from Fujitsu Network Communications, Inc. of Richardson, Texas, and Orckit Communications Ltd., Tel Aviv, Israel.

Meanwhile, BellSouth plans to offer ADSL services in 30 cities by year's end, including Charlotte, Ft. Lauderdale, Jacksonville, New Orleans, and Raleigh. Called BellSouth ADSL, the service will offer a maximum downstream rate of 1.5 Mbps and an upstream rate of 256 Kbps for a monthly rate starting at $45. will also bundle the service with its Internet offering, charging $200 for a DSL modem and a $100 installation fee.

Bell Atlantic, which pioneered ADSL technology, became the last RBOC to unveil its service plans when it announced that Washington D.C., Pittsburgh, and Philadelphia would be the first cities to get the new offering, starting this month. New Jersey will come onstream in October, with Boston and New York to follow in 1999. Initially, Bell Atlantic will provide ADSL service using carrierless amplitude phase modulation, but will switch to DSL.Lite when the standard is finalized. It uses equipment from Westell Technologies and DSC Communications Corp. Through its subsidiary, the carrier will offer three ADSL speeds: up to 640 Kbps for $69.95 a month, up to 1.6 Mbps for $109.95, and up to 7.1 Mbps for $189.95. Getting started costs less than $200, and current ISDN customers can upgrade to ADSL service at no additional charge.


Network vendors are also increasing the pace of DSL product introductions. Cisco recently rolled out eight new DSL products, four for customer premises and the others for carriers and ISPs, while 3Com unveiled an ADSL router and an internal and external ADSL modem. Together, the Cisco products offer users end-to-end solutions for Internet access at rates to 8.1 Mbps.

Cabletron entered the market by acquiring two DSL specialists, FlowPoint Corp. of Los Gatos, Calif., and Ariel Corp of Cranbury, N.J., for a total of $58 million. FlowPoint makes customer premise DSL and ISDN Internet and intranet access routers, while Ariel provides end-to-end, ADSL-to-ATM systems for high-speed Internet access.

In addition, Paradyne Corp. and Nortel have introduced alternative technologies that provide the same high-speed access. Paradyne's HotWire MVL (multiple virtual line) systems allow up to eight simultaneous users to share up to 768 Kbps of bandwidth over a single copper wire. With MVL, a user can employ the entire bandwidth to download or upload a file, or run in symmetrical mode to handle videoconferencing, say, at 384 Kbps full duplex. As more people use the service, the bandwidth is dynamically allocated between applications.

Nortel's EtherLoop technology effectively stretches the LAN connection over existing copper phone lines, delivering Ethernet packets over distances to 21,000 feet while carrying normal voice traffic over the same line. Rates vary from 9 Mbps over distances of up to 2,000 feet to 800 Kbps at 21,000 feet. Nortel sells its products to CLECs, which bundle the equipment with a high-speed Ethernet connectivity service based on EtherLoop.

RELATED ARTICLE: DSL takes many forms

Digital subscriber line (DSL) services operate over existing copper telephone lines without interrupting voice traffic, allowing users to consolidate their data and voice lines. They come in a variety of formats.

For telecommuters requiring high-speed Internet access, asynchronous DSL (ADSL) service is expected to be the most popular, since it matches the asymmetric pattern of Internet traffic, where user queries, messages, and other data account for a fraction of the inbound responses. ADSL inbound rates may reach up to 6 Mbps and outbound rates to 640 Kbps. ADSL operates over distances of up to 18,000 feet of 24-gauge copper pair wire. Since 80% of telco customers in the U.S. are reportedly within 18,000 feet of a central office, ADSL is suitable for small businesses and users in home offices as well as telecommuters.

ADSL was developed by the telephone companies to bring video-on-demand to regional customers to compete with cable TV firms. When such services foundered, ADSL was shelved, only to be revived by the popularity of the Internet and corporate intranets and growing user demand for high-speed access.

All the dedicated, non-switched service requires is a modem at each end to split the voice from the data traffic and create separate channels for the upstream and downstream data.

Rate-adaptive DSL (RADSL) is a variant of ADSL, where the speed adjusts downwards to accommodate poor line conditions or to create symmetric upstream and downstream speeds.

Universal DSL (USDL), or DSL.Lite, is a standard supported by the Universal ADSL Working Group, an alliance formed by Microsoft, Intel, Compaq, and others. Based on a scaled-down and enhanced version of ADSL that requires less bandwidth, UDSL can be activated from a central office without sending a technician to install a splitter.

High-data-rate DSL (HDSL) provides a symmetric service of 1.544 or 2.048 Mbps in each direction. It serves as a T1/E1 alternative. Two twisted-pair lines are needed for the lower-speed offering and three for the faster service. Single-line DSL (SDSL) also provides 1.544 or 2.048 Mbps in each direction, but the service only needs one twisted pair. HDSL's operating range extends to 12,000 feet, while SDSL is limited to 10,000 feet.

Very-high-data-rate DSL (VDSL) can operate at speeds to 52 Mbps downstream and 2.3 Mbps upstream, making it suitable for high-speed Internet access, video on demand, and interactive multimedia applications.

ISDN-based DSL (IDSL) is targeted mainly at small and home offices. It provides a symmetrical service of 128 Kbps in each direction using ISDN equipment. IDSL defines only the physical line code, so it can be used with existing customer premise equipment and a variety of protocols supporting ISDN, analog, and frame relay services. As such, it is likely to serve as a bridge between current hardware environments and future, more advanced DSL services.

Edwards is program chairman of NetCom, the Network Computing Solutions Conference and Exposition, which will be held in Ft. Lauderdale, Fla., Feb. 16-18, 1999, and in Anaheim, Calif, on Sept. 21-23, 1999.
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Title Annotation:Technology Information; includes related article on the many forms of DSL; digital subscriber lines
Author:Edwards, Morris
Publication:Communications News
Date:Sep 1, 1998
Previous Article:GTE phones home.
Next Article:Breaking the storage bottleneck

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