Digital Subscriber Line

Faster connections for PCs for telecommuters, branch offices

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Still, the average DSL installation costs about $100. Monthly fees for lower-speed services at 256K bit/sec. range from $40 to $50, which is comparable to cable modem fees.

Some PC makers are beginning to install DSL modems inside their boxes, making installation even simpler than before. By fall, some DSL service providers will offer packetized voice-over-DSL service, which could be valuable for small businesses that want to run up to 24 digital voice connections over a single copper line at the cost of the single line, Sheppard says.

Despite all the promises of speed from cable and DSL, Harris says, some users who expect 2M bit/sec. speed will still be slowed down over portions of the Internet backbone, which might reach speeds of only 500K bit/sec. Both technologies are really speeding up connections only locally for the "last mile" from a service provider's central office to a home or business, sometimes employing fiber-optic cable in addition to either coaxial or copper cables.

Though just a year ago some DSL installations might have taken several weeks, the industry now averages one to three weeks, Sheppard says. Sometimes a service provider can turn on DSL service without even sending a truck to a home.

Sheppard says the following are key considerations for an IT group shopping for DSL:

  • Look for a service provider guarantee of bandwidth within the stated price.
  • Weigh other service-level guarantees, such as uptime and payment procedures for downtime.
  • Seek around-the-clock phone support for the service, not just Internet support.
  • Consider whether the service provider offers DSL in all parts of the U.S. where your company has operations, so all workers can be equally productive and billing can be centralized.
  • Ask whether the service provider will be offering packetized voice-over-DSL or video services for teleconferencing.
  • Flavors of DSL
    Few abbreviations have spawned as many terms as DSL. Here's a rundown of some of the terms we've seen.
    ADSLAsymmetric DSL, which has high-speed downloads but slower uploads
    DSL-Lite Limits download speed to 1M to 1.5M bit/sec. and uploads to 100K to 200K bit/sec.
    DSLAMDigital Subscriber Line Access Multiplexer, which concentrates many ADSL subscriber lines on a single Asynchronous Transfer Mode line
    HDSL High data-rate DSL, capable of T1 or E1 speeds
    ISDL DSL that uses ISDN technology to deliver 128K bit/sec. to an IDSL modem bank
    RADSL Rate-adaptive ADSL, where modems test the line and adapt their speeds accordingly
    SDSL Symmetric DSL, which has equal upload and download speeds
    VDSL Very high bit-rate DSL, which has speeds of 12.9M to 52.8M bit/sec.
    xDSL A way to refer generically to types of DSL

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