ADSL stands for Asymmetric Digital Subscriber Line. ADSL is a modem technology that transforms phone
lines into high speed digital lines for fast Internet access.
How it works
ADSL modems use digital coding techniques to "turbo charge" phone lines, results are up to 90% faster
than non ADSL modems. ADSL provides speeds up to 8Mbps downstream (to the user) and up to 1Mbps
upstream (from the user), depending upon the line length
and line conditions. This type of speed fits well with information received from the Internet.
Benefits of ADSL
 | | Simultaneous Internet and voice/fax capabilities over existing phone lines |
| | Fast Internet connection |
| | Full time "always on" connection |
Limitations of ADSL
| | Distance limitation (you must be roughly 18,000 cable ft from the phone company) |
| | Availability (not available in all areas) |
| | Initial set up, modem and monthly fees vary across regions (as much as 50%) |
Hardware Requirements for ADSL (Assumes PCs are connected to a LAN)
| | 486 or better (Pentium recommended) |
| | Windows 3.1 95/98/ NT |
| | 8MB RAM and 25 MB hard disk space |
| | DSL Modem |
| | Ethernet Card |
| | Router
|
Cable Modems
A cable modem is a device that hooks up to your computer and gives you high speed Internet access
through your cable TV network instead of through your telephone line. Cable modems enable data
connections at very high speeds, receiving data up to 10 Mbps and sending data up to 2 Mbps (some up
to 10Mbps)
Benefits of Cable modems
| | Very high transmission speeds |
| | Lines are always open (no dialing in) |
| | Multiple users on a single coax connection |
Limitations of Cable Modems | | Availability (contact your local cable company) |
| | Shared bandwidth, performance may vary depending on location |
Contact your local cable company for availability. When you sign up for cable modem service an
installer will install a card in to your computer (10BaseT ethernet) that will split the coax cable (so
you can watch TV and surf the Internet at the same time). The installer will also install your cable
modem to your PC.
Hardware Requirements for Cable Modems
(assumes PCs are connected to a LAN)
| | 486 PC, (Pentium recommended) |
| | Windows 3.1, 95/98, NT |
| | 16MB RAM |
| | 125 MB Disk Space |
| | Ethernet Card |
| | Router |
What is the difference between ISDN and ADSL?
ISDN provides two voice channels or a 128Kbps data channel while ADSL is predominantly a data channel
providing an asymmetrical bandwidth of up to 8 Mbps downstream and 1 Mbps upstream under good conditions.
ISDN has a usage (per minute) fee, ADSL does not. Distance limitations can be solved with ISDN, ADSL has
strict distance limits.
What is the difference between ADSL and Cable modems?
ADSL provides a dedicated service over a single telephone line; cable modems offer a dedicated service
over a shared media. Cable modems have a greater downstream bandwidth (up to 30 Mbps), however the
bandwidth is shared among all users on the loop, therefore as more users go online (join the loop) the
performance may vary (perhaps dramatically).
What is the difference between ADSL , ISDN and Analog modems?
Today's analog modem lines routinely offer 28.8 Kbps to 33.6 Kbps and in a few instances up to 56Kbps.
56K Kbps is probably the practical limit for analog modems. ISDN can increase this to 128Kbps, ADSL
between 144Kbps - 8Mbps. ADSL in not available in all areas, ISDN has been around for several years
and is more widely available, analog modems are available in all areas. ADSL is not well suited for
video conferencing due to large amount of data flowing in both directions.
| Type |
Strengths |
Weaknesses |
Bandwidth |
Pricing Elements |
| ISDN |
High speed, very reliable, available in most areas |
Tariff charges, can be complicated to install, requires dial-up to connect |
64Kbps to 128Kbps |
Installation charge, Monthly charge,
Usage charge |
| ADSL |
Very high speed, dedicated always on |
Availability, distance limitations |
256Kbps to 8Mbps |
Installation charge, Monthly charge |
| Cable Modems |
Very high speed, moderately priced. |
Shared media, not widely available for small business |
Up to 3Kbps in most areas |
Installation charge, Monthly charge |
| Analog Modems |
Wide availability |
Limited bandwidth |
19.2-56.6 Kbps |
Monthly charge |
Questions to ask your service provider:
Ask the DSL provider if its line will have a dial tone or is data only. Baby Bells offer voice and data
(and more options in the future).
Who does the configuring? Ask the provider if its installers will configure your system for access and
test it before leaving. If not, ask it to send your configuration information before the line installers
arrive.
Who handles support? If services are provided by separate partners, make sure you have technical support
contacts for both your ISP and your line provider before installation.
Does it work with my ISP? Check with your Internet Service Provider and ask if they support DSL.
Glossary of terms
ISDN:
Integrated Services Digital Network
ADSL:
Asymmetric Digital Subscriber Line
Asymmetric Digital Subscriber:
A method of data communication in which the transmission of bits of data isn't synchronized by clock
speed, but is accomplished by sending the bits one after the other, with a start bit and a stop bit to
mark the beginning and end of each data unit.
Transmissions speeds are most often measured in bits per second (b/s or bps). Commonly used abbreviations are:
Kb/s or Kbps
(Kilobits per second): Thousand bits per second
Mb/s or Mbps
(Megabits per second): Million bits per second
Gb/s or Gbps
(Gigabits per second): Billion bits per second
Bandwidth:
A frequency measurement expressed in cycles per second, the amount of information that can
flow through a channel.
Downstream:
Data sent from the host (Internet) to the user.
Upstream:
Data sent from the user to the host.
Router:
An electronic device that examines each packet of data it receives and then decides which way
to send it onward toward its destination.
Summary
One thing is certain, if you're not conducting business over the Internet you soon will be. Our future
business model is based on the Internet and is compatible with today's digital technology.
How you and your company access the Internet will be up to you. This document presents an overview of
digital internet access vs. analog access methods.
When choosing a digital service provider ask yourself the following questions:
| | How many workstations need Internet access? |
| | What speeds (bandwidth) are appropriate for my business? |
| | Will I send large files across the internet or receive them? or both? |
| | How much can I afford? |
Most service providers offer plug and play packages that include everything you need, i.e. installation,
service, routers, adapters, modems and lines. As a general rule most metropolitan agencies will have no
problem finding a digital service to fit their needs. Rural agencies will find limitations due to their
location and will have fewer choices.
The best source for information on digital services in your area is your local phone company or service
provider.
Good, better, best ratings for personal computers accessing the Internet
GOOD Configuration for Internet Access
| | CPU running Windows 95 at 75 MHz |
| | 16 MB of random access memory (RAM) |
| | 33.6K Modem |
| | 14" Monitor |
| | 500 MB Hard Drive |
BETTER Configuration for Internet Access
| | CPU running Windows 98 at 366 MHz |
| | 64 MB of random access memory (RAM) |
| | 56K / V.90 Modem |
| | 15" Monitor |
| | 4.3 GB Hard Drive |
| | 40X CD-ROM Drive |
BEST Configuration for Internet Access
| | CPU running Windows 98 at 600 MHz |
| | 128 MB of random access memory (RAM) |
| | 56K / V.90 Modem |
| | 17" Monitor |
| | 20.4 GB Hard Drive |
| | 8X DVD-ROM Drive |
As a general rule of thumb, it is safe to say that you can never have too much RAM, too big a monitor,
too fast a processor or too big a hard drive.
Source: IIAA Agents Council for Technology
