DSL puts users on fast track
- By Cheryl Gerber
- Aug 30, 1998
It takes time to translate new technology into common tools that are cost-effective and easy to deploy. However, Digital Subscriber Line (DSL) has begun to reward the trust of pioneering federal users by proving to be an efficient, economical way to quickly send and receive data across existing copper telephone lines. And although the service has seen its greatest use within government on private networks, it will become available to more users as local phone companies begin offering it more widely and PC vendors begin equipping machines with DSL-ready modems.
DSL is not only inexpensive, it's fast— faster than Integrated Services Digital Network (ISDN) and much faster than traditional modems. Bob Deutsch, director of federal engineering at Cisco Systems Inc., provided an example: It takes five hours to download a six-minute video using a 28.8 kilobits/sec modem; over ISDN, it takes one hour. But you could complete the same task over DSL in 10 minutes.
DSL technology comes in many flavors that are differentiated largely based on transmission speeds. Asymmetrical DSL (ADSL) delivers rates of 32 kilobits/sec to 8.192 megabits/sec downstream to the customer and 32 kilobits/sec to 1.088 megabits/sec upstream to the network. Synchronous DSL (SDSL) provides bi-directional communications at data rates ranging from 160 kilobits/sec to 2.084 megabits/sec. High-bit-rate DSL (HDSL) technology can transport at T-1 (1.544 megabits/sec) or E-1 (2.048 megabits/sec) rates.
Basically, DSL is composed of a pair of modems— at both ends of a copper wire— that concurrently support a normal voice call and a high-speed data call. A ''splitter box" at the customer's end separates the DSL signals from the voice signal, and the splitter box connects to a DSL modem that in turn connects to the user's PC. Phone companies' central offices must be equipped with a DSL Access Multiplexer to connect the normal phone signal to the switched telephone network and route the DSL signal to an Internet backbone connection or directly to another DSL user. In its current form, DSL is limited to distances of no more than three miles. But that constraint could be short-lived. Kieran Taylor, a product manager at Bay Networks Inc., Santa Clara, Calif., said the entire industry is focused on overcoming that hurdle.
DSL technology also has some interoperability constraints. ''One vendor's ADSL doesn't always work with another vendor's implementation of ADSL," said Ken Hohhof, president of Westell WorldWide Services, Aurora, Ill. ''But all flavors of DSL technology do coexist on the same cable."
Another obstacle has been the difficulty of installing DSL on public networks. Although the Telecommunications Reform Act of 1996 mandated that local exchange carriers install DSL equipment in their central offices, the implementation of that law has been slow to see the light of day. To be fair, the telephone companies have made progress. ''DSL was stalled for a long time," said Jay Pultz, research director of wide-area networks at Gartner Group, Stamford, Conn. ''But that has changed dramatically in the last year. The telcos are now on an aggressive schedule to roll out their DSL products by the end of this year." Indeed, US West was the first to offer full ADSL early this year, Bell Atlantic is now introducing it in Washington, D.C., and Philadelphia, and long-distance provider AT&T will kick off ADSL trials in October.
However, federal agencies running private networks control their own central offices and do not need to go through the telephone company to implement any type of DSL. For example, the Marines Corps at Camp Lejeune, Jacksonville, N.C., began installing 300 Westell Technologies Inc. Flexcap2 modems a year ago. The base now has installed 200 Rate Adaptive ADSL (RADSL) modems in 200 buildings. RADSL is a version of ADSL that scales to different speeds. Each RADSL modem at the Marine facility has increased connectivity speed from 56 kilobits/sec to 2.24 megabits/sec downstream and to 1.08 megabits/sec upstream. ''We have not had one failure," said Terry Maxwell, the network manager at the base. ''[The RADSL modems] have been very reliable."
Camp Lejeune has a fiber-optic Asynchronous Transfer Mode (ATM) backbone but cannot afford to tear out the existing copper wires and install fiber in every building. For buildings with medium to low network requirements, the camp uses the RADSL modems connecting to the ATM backbone via a Cabletron Systems Inc. enterprise switch. The cost of using RADSL averages $1,500 per connection/building, compared with $3,000 to $4,000 per connection for fiber optics. Maxwell bought the modems off Westell's General Services Administration schedule contract.
The broader bandwidth provided by the RADSL modems has improved mainframe access, file transfer and support of client/server applications. ''Through the use of RADSL, the base has been able to take greater advantage of the increased number of DOD-centralized applications," Maxwell said. The Marine base also has conserved file server resources. Rather than maintaining one file server for 24 people, the base can now use two file servers in a central network center for 100 people.
To expand its existing local-area network and upgrade its ISDN, the Marine Corps Air Station Miramar, San Diego, began installing Westell RADSL modems last year. Today the base has RADSL installed at 14 sites and has increased the speed of access to its campus-area network from 64 kilobits/sec with ISDN to about 2 megabits/sec downstream and 1 megabit/sec upstream, according to Jeannie Allen, the air station's network operations manager.
FAA Center Flies With SDSL
A few federal agencies have used the services of Internet SDSL providers— which are Internet service providers that connect users to the Internet via DSL as opposed to using modem pools— to initiate their forays into World Wide Web site hosting. A team technology center within the Federal Aviation Administration's Human Resources Division is using an SDSL connection to speed up Internet and intranet surfing and to prepare for hosting several office Web sites. The technology center chose SDSL instead of T-1 connections for Internet access because of the cost savings. A bi-directional 1.54 megabits/sec T-1 connection would have cost $2,500 to install plus $1,500 per month, said Nader Ghobadi, the center's technology manager. Instead, Ghobadi chose SDSL Internet service provider DigitalSelect, Sterling, Va. "The DSL connection gives us everything we need," Ghobadi said. "We can get up to 768 kilobits/sec in either direction. So far it's been a great investment for us. It was only $400 per month plus the $500 initial installation fee."
DigitalSelect installed an SDSL router and worked with Bell Atlantic to install a separate unfiltered telephone line at the FAA center to get the full bandwidth of SDSL. "It took a month to get the service going, but 90 percent of that was waiting for Bell Atlantic to install another phone line," Ghobadi said. "The Bell Atlantic technician had to come back twice, and even then it was wired incorrectly."
This wasn't the first time that Digital-Select had run into a snag with Bell Atlantic phone lines. "We often find that the Bell Atlantic installation process becomes the hardest part of setting up a customer," said Craig Bowman, DigitalSelect's vice president. "We've learned ways to manage Bell Atlantic and the installation of the DSL phone lines to ensure [that] they are installed correctly and in a timely fashion."
A Bell Atlantic spokeswoman said the company is trying hard to meet the demand from DSL users. "Since the 1996 Telecommunications Reform Act passed, Bell Atlantic has spent $1 billion and dedicated 1,000 employees to meet the requirements," she said.
Shopping for Options
The Chemical Safety and Hazard Investigation Board had a similar experience with Bell Atlantic delays.
"It took a month to get a second line installed," said Robert Miller, the information systems manager for the board. "Two days later, DigitalSelect came in and installed the DSL equipment."
This month, after determining how to provide Internet access, the board eliminated ADSL as an option, Miller said. "If you are hosting a Web server, you don't want to run it on ADSL," he said. "Asymmetric is set up with fast download speeds and not-as-fast upload speeds."
Then the board ruled out ISDN after determining that ISDN lacked the ability to scale up to T-1 speeds and that it was too expensive. The board then settled on DigitalSelect's Internet SDSL connection.
"I wanted a high-bandwidth and scalable solution that would allow me to host a Web site on a Web server here," Miller said.
He said the board pays $300 a month for a 256 kilobits/sec connection. The pricing is one-sixth the cost of a full T-1 line, and the service runs at five times the speed of a 56 kilobits/sec modem, Miller said. Because the firmware within SDSL is scalable, Miller noted that he can upgrade without changing hardware.
So Long, Slow Modems
Claudia Bacco, senior analyst at Telechoice Inc., said DSL's biggest competitors in the federal and business markets are T-1 and frame relay. She said most T-1 users are unlikely to convert to DSL, but many ISDN and modem users eventually will move to DSL technology.
In fact, industry experts acknowledge that higher-speed DSL modems will overtake the current installed base of modems. "The window of opportunity for the 56-kilobit modems is drying up," Cisco's Deutsch said. "If I can bring the price of DSL down to that of 28.8 modem prices, then what's the point of 28.8? People will stop buying 28.8 modems."
Another form of ADSL, called G.Lite, is scheduled for approval as an international standard this fall. G.Lite is a scaled-down PC version of the technology. Once it becomes a standard, PC manufacturers will introduce dual-function, 56 kilobits/sec, DSL-ready modems with their PCs, Gartner's Pultz said.
Although industry observers said DSL remains in the early phase of its development, they believe the technology is on its way to becoming the next most economical and efficient means to expand PC communications. Deutsch said four factors will contribute to the growth of DSL. "The pricing will be more competitive [than other technologies]," he said. "It's easier to deploy over existing infrastructure. There's a huge demand from users who would love to get higher speeds. And there are far greater competitive pressures in this market."
-- Gerber is a free-lance writer based in Kingston, N.Y.
AT A GLANCE
Status: Some federal agencies running private networks have begun using DSL to speed up data transmission over existing copper wire. But problems regarding interoperability and DSL's availability on public networks have hindered the technology's progress.
Issues: Cost and speed. Users have found that they can transmit data less expensively with DSL than via Integrated Services Digital Network technology or by installing T-1 lines. DSL also significantly increases data rates beyond speeds achieved through traditional modems.
Outlook: Good. Advances such as a version of DSL designed for PCs will combine with the technology's cost and efficiency advantages to make it attractive to a greater base of users.