Pros and Cons of DSL


Nearly all federal agencies have their desktop computers wired to a local-areanetwork to share files. The departmental server is typically connected tothe agency's network to provide access to a central database and other sharedinformation. The server also usually connects to the Internet, using a fastT-1 or T-3 connection, so that computer users have direct access to theInternet and all of its resources.

But while that is a typical network access model for offices in Washington,D.C., and other large installations, what about small field offices, suchas military recruiters, remote research organizations or the growing ranksof federal telecommuters?

Should those federal users be exiled to the land of network access viaslow, squawking dial-up modems? Not necessarily. Today, remote access solutionsfor federal users are available in a variety of systems and at prices thatcan provide even the smallest office or part-time worker with immediate,full-time network access at high speeds.

"Whether it is one day a week or two hours after dinner, it is a frustratingexperience to work with the size of files today with a dial-up connection,"said Jeanne Schaaf, a senior analyst at Forrester Research, Cambridge, Mass.

Permanent Internet access is important for far-flung federal officesbecause it lets remote locations connect to the main office to create avirtual private network (VPN). That means that a lone weather researcherin Point Barrow, Alaska, has electronic access to all the same informationand services as a PC user at the National Weather Service headquarters.

The two most popular high-speed access technologies these days are cablemodems and Asymmetric Digital Subscriber Line (ADSL) systems. These arebecoming mass-market technologies that can nevertheless provide very cost-effective,always-on Internet access for small federal offices and telecommuters.

Each has its own advantages and disadvantages, but those differencesare not so great as proponents of either technology might have you believe,according to industry analysts.

Cable modems work by connecting a computer via a special modem to thewideband coaxial network of a local cable TV system. A modem at the otherend of the network connects the system to the Internet. Cable modems provideblazingly fast maximum network speed, but they do have drawbacks. Becauseusers share cable bandwidth with every other home or office on the localnode, access speeds will drop as more users compete for a slice of the network.

Cox Communications Inc., one of the nation's largest cable televisioncompanies and a service provider in the Washington, D.C., metro area, iscurrently building a cable modem system and plans to target federal customersaggressively once the system is in place. "The federal government is goingto be a key market once the network is finished," said Sam Attisha, managerof national accounts, federal and education. "Telecommuting becomes a viableoption for federal employees once they have this in their homes, especiallyif you look at it 12 months from now."

The Navy's Space and Naval Warfare Systems Command in San Diego is alsolooking at using Cox's cable modem service to let its employees avoid SouthernCalifornia traffic, according to Jeff Siconolfi, operations manager forthe automated communications management system at Spawar. Cox's cable modemInternet access service costs as little as $30 a month for speeds as highas 1.5 megabits/sec (downloads) and 192 kilobits/sec (uploads).

The primary limitation on cable modem use for federal agencies is thefact that most cable TV service is installed in residential areas, not officebuildings. So cable modems are probably most useful for telecommuting federalworkers.

This reach into workers' homes has given cable a significant edge overother solutions in adoption rates, according to Schaaf. By the end of theyear, there will be 742,000 customers for cable modem service, comparedto 253,000 for ADSL, she said. By 2003, the numbers will be 3.9 millionfor cable and 1.8 million for DSL, Schaaf predicts.

A knock against cable modems is that the shared bandwidth could compromisea user's security because other users on the same node might be able togain access to data. Attisha says that isn't a problem, but Cox has begunencrypting communications just to be sure.

"The number of attacks that come from your next-door neighbor are relativelyfew and far between," said Fritz McCormick, an analyst for The Yankee Group,Boston. But cable and DSL are both vulnerable because they are always on,which could give hackers a chance to attack the system. The solution ineither case is to use firewall software, McCormick said.

Pros and Cons of DSL



ADSL isn't as fast as cable, but its speed doesn't slow during periodsof heavy use. Service is available that can provide download speeds of640 kilobits/sec, 1.6 megabits/sec and 7.1 megabits/sec, for $40, $60 and$110 a month, respectively. Uploads are only 90 kilobits/sec, except onthe 7.1 megabits/sec download service, where they slow to 60 kilobits/sec— about the same as a fast dial-up connection today.

ADSL has the advantage of going most anywhere telephone wires are available.But ADSL has its limits too. The most significant is degradation of serviceaccording to a user's distance from the local phone switch. Performancevaries depending on the equipment used, but customers who have more thanabout 12,000 feet of wire between their telephone and the local telephonecompany's switch can't get ADSL because the speed drops off precipitouslybeyond that distance.

That means that many suburban residential locations are out of reach,but commercial office buildings are likely to fall within the service area."We have had some interest expressed by the federal government for teleworkingapplications," said John Eidsness, senior manager for product managementat Bell Atlantic Federal. "Any agency that depends on knowledge workersis looking for ways to facilitate these people working at home."

ADSL is available on the General Services Administration's Cinema contract,but so far only the World Bank has taken advantage of the service, accordingto GSA spokesman Bill Bearden. World Bank is conducting a two-month pilotfor its remote users in the Washington metro area.

"World Bank chose the remote IP access DSL option, which includes dualaccess for both the Internet and their internal intranet," he said. "Uponcompletion of the pilot program, they will determine whether to expand DSLservices to all their employees or not."

A problem with ADSL is the asymmetric nature of the technology. Thatmeans that it receives data much faster than it sends it. So if a federaloffice sends a lot of data upstream to the home office, ADSL may not befast enough.

For heavy-duty uses, there are two more versions of DSL available thataddress speed concerns. Symmetric DSL gives users equally fast speeds upstreamand downstream. Such service is more expensive than ADSL, with its consumer-friendlypricing. But if an office needs full-speed data flow in both directionsand makes keeping the service up and running a priority, then SDSL is theway to go.

"Business users are often sending as much data as they are receiving,"said Tim Suh, product manager for DSL service at UUNet Technologies Inc.The company's UULink SDSL service provides a 128 kilobits/sec connectionfor as many as 20 users and gives them static Internet Protocol addressesand Post Office Protocol 3 mailboxes for $149 a month. The service is availablein faster speeds up to 1 megabits/sec, for $599 a month.

For federal installations that are so large that they have their ownphone systems and dedicated T-1 or T-3 connections to the Internet, DSLtechnology makes it easier to connect all of the PCs in their area to theirnetwork without having to run cables to every building and office.

OAO Corp. recently added SDSL service to its GSA Select Services contractand has gotten a good response. "We are seeing a lot of interest acrossthe civil agencies," said OAO spokeswoman Eileen Mowle. It is especiallyattractive to agencies that want fast speeds, but that don't want to spendthe money for fiber- optic connections, she said.

Rate Adaptive DSL (RADSL) lets spread-out federal installations connectcomputers in all of their facilities to the central network. The U.S. Marinebase at Camp Lejeune, N.C., uses RADSL to connect 300 of its smaller buildingsto the base's network (see Case Study).

"A key application [for RADSL] is deploying high-speed connections ina campus," said Bill Rodey, vice chairman of the DSL Forum. "DSL is an excellentconnection technology to get LAN-type speed over copper wires," he said.

-- Carney is a freelance writer based in Herndon, Va.

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