ADSL
by Dennis Roe
Tulsa Computer Society
From the December 1999 issue of the I/O Port Newsletter
DSL Description
DSL is a high speed, point-to-point digital connection that uses regular copper telephone lines to simultaneously transmit voice and data. FasTrakSM DSL , the variety of DSL we're now offering, is asymmetrical-data travels faster downstream, where end users need more bandwidth, than upstream. FasTrakSM DSL sends data downstream to the user at speeds from 1.5 to 6.1 Mbps and upstream at speeds of 128 or 384 Kbps. The term 'xDSL' appears frequently in descriptions of this technology. xDSL is a generic term that includes several variations:
| ADSL | Asymmetric Digital Subscriber Line | 1.5 Mbps/64 -384 Kbps |
| HDSL | High-bit-rate Digital Subscriber Line | 1.5 Mbps/1.5 Mbps |
| SDSL | Single-line Digital Subscriber Line | 1.5 Mbps/1.5 Mbps |
| VDSL | Very high rate Digital Subscriber Line | 13 -52 Mbps/1.5 -2.3 Mbps |
| IDSL | ISDN Digital Subscriber Line | 128 Kbps/128 Kbps |
| RADSL | Rate Adaptive Digital Subscriber Line | various speeds |
DSL uses a standard subscriber line, the same unshielded, twisted-pair telephone line that carries your regular telephone calls. It divides the available bandwidth into low and high-frequency channels so users can simultaneously transmit analog voice service and digital data service on this single line. It's an ideal solution for high-speed Internet or corporate LAN access from the end users' perspective: they get more throughput for the applications they use most, without having to install new infrastructure.
DSL Fact Sheet
Why 'breakthrough threshold' access?
DSL answers the demand for ever-increasing bandwidth to the desktop:
- Internet traffic doubles every 100 days.1
- More than 20 new hosts are added to the Internet every minute.2
- Two of five American employees are expected to have remote LAN access by the end of 1999.3
- The U.S. has experienced a threefold growth in telecommuting during the 1990s.4
- As compared to 1998, the number of Americans making online purchases will double in 1999.5
What are the benefits?
DSL is:
- Fast. DSL is up to 200 times faster than current modem connections.
- Always on. DSL is always on, always available, always dedicated.
- Versatile. With voice over data, DSL is a phone line and data line in one.
- Affordable. Our affordable DSL packages offer the speeds end users need at substantial savings over other broadband alternatives.
- Secure. Cable modem access is shared topology, which means unprotected, shared resources are visible to other users. DSL uses dedicated, secure topology.
What speeds are available?
- 1.5 Mbps to 384 Kbps downstream; 128 Kbps upstream
- 6.1 Mbps to 1.5 Mbps downstream; 384 Kbps upstream.
Actual downstream speeds may be affected by:
- The end user's distance from the serving central office
- Other digital services in the same cable sheath
- The quality of the existing phone line (load coils, bridge tap, etc.).
Where is it available?
In 1999, we're deploying DSL in 271 central offices in Southwestern Bell and 255 central offices in Pacific Bell. These DSL-compatible offices serve 3.2 million residential customers and 440,000 business customers in Southwestern Bell and 5 million residential customers and 900,000 business customers in Pacific Bell.
Due to technical limitations, we can't provide DSL past 17,000 from the central office.
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Tulsa Computer Society 11/9/99
Don Singleton, President
djs@ionet.net