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What
does DSL stand for?
Digital Subscriber Line. DSL is a modem technology that
transforms ordinary phone lines (also known as "twisted
copper pairs") into high-speed digital lines for ultra-fast
Internet access. DSL also enables access to corporate
networks for telecommuters, as well as exciting new interactive
multimedia applications such as multiplayer gaming, video
on demand and video catalogs.
Are there any per-minute or usage charges
associated with DSL?
No. DSL is a dedicated network service that costs
the same regardless how often it is used or how much data
is transferred. This predictability is one of xDSL's most
attractive features. However, on the residential/consummer
product, there is a limitation in that a Dynamic IP assignment
is used by "forcing" the IP to change after 10 Minutes
of idle time or after a continuous 8 hour session. There
is no need to "dial in" again, as there is no dial in
process to begin with. The IP is simply changed after
exceeding those limitations. |
How fast is DSL?
The following chart shows the speed comparison from analog to
digital:
| TYPE
OF DATA |
FILE
LENGTH |
28.8
- KBPS MODEM |
56k
V.90 MODEM |
ISDN
- 128 KBPS |
DSL
- 384 KBPS |
DSL
- 1.5 MBPS |
| Browsing
the Net - 25 web pages with text and graphics
|
2.5Mb
|
12
minutes |
9
minutes |
2
½ minutes |
52
seconds |
13
seconds |
| A
20 sec video |
8Mb
|
37
minutes |
28
minutes |
8
½ minutes |
2
¾ minutes |
43
seconds |
| Download
entire Netscape 4.0 or Internet Explorer 4.0 browser software
|
25Mb
|
120
minutes |
90
minutes |
26
minutes |
8
2/3 minutes |
2
1/5 minutes |
What
is xDSL?
xDSL is the name which has been coined for the family of digital
subscriber line technologies ranging from ADSL to SDSL. The
"x" represents a varible that can be replaced with either the
"A" standing for ASYNCHRONUS or "S" standing for SYNCHRONUS.
How does xDSL work?
xDSL modems use digital coding techniques to squeeze up to 99%
more capacity out of a phone line without interfering with your
regular phone services. That means you could be simultaneously
talking on the phone or sending a fax - while surfing the World
Wide Web, since the DSL service operates off another separate
phone circuit and does NOT need to tie-up your current voice
and/or fax line.
What are the main benefits of xDSL?
- Uninterrupted, high-speed Internet access that's always on-line
- Cost-effective solution for residential customers, telecommuters
and small businesses - Data Security that exceeds other technologies
What is the market for xDSL?
xDSL enables two general types of applications -- interactive
video and high speed data communications. Interactive video
includes movies on demand, other video on demand such as delayed
TV segments, video games, video catalogs, and video information
retrieval. Data communications covers Internet access, telecommuting
(remote LAN access), and specialized network access. The strength
of xDSL compared to other high speed transmission alternatives
(such as cable modems or Fiber To The Neighborhood (FTTN) lies
in the number of existing telephone lines -- now approaching
750 million -- compared to new cabling which has reached comparatively
few homes and almost no small businesses.
What will xDSL do to ISDN?
That all depends upon the telephone companies offering both
services. The two services are not the same -- ISDN provides
two voice channels or a 128 Kbps data channel while xDSL is
predominantly a data pipe providing an asymmetrical bandwidth
of up to 8 Mbps downstream and 1 Mbps upstream under good conditions.
However, an xDSL access network will be an overlay network and
therefore will not require the expensive and time-consuming
switch upgrades that held ISDN back for so long. If xDSL service
prices resemble ISDN service prices, then one would expect xDSL
to be favored for Internet and video applications.
What determines which level of service is
available to you?
DSL is a distance-sensitive telecommunications service: increased
distance from the central office (CO) means decreased speeds.
The closer one is to the CO, the more bandwidth that can be
provided.
What is IDSL? The "I" in ISDL stands for ISDN. This is for those
customers of yours that may already have ISDN service. The IDSL
level of service would be used for those that have the ISDN
circuit in place and want to convert over to using DSL. Using
IDSL is the easiest way to do so.
Does DSL have any security issues like cable
modems?
No. DSL is not a shared network service like cable modems, which
means that one end-user can not see what's on a neighbor's computer
using DSL. The service is a private dedicated connection from
the end-user to the network.
Will DSL interrupt existing phone service?
No. DSL works on its own phone line. An end user will never
experience slower performance when making phone calls.
Can I use a telephone or fax machine on my
DSL line?
No. DSL uses a digital technology (DSL) that is not yet compatible
with telephones and fax machines.
Can the Internet keep up with so much speed?
The Internet infrastructure is constantly being upgraded to
handle the rapidly increasing use of the Internet. Many servers
operate at 56 Kpbs. In addition, the Internet backbone has grown
in an unplanned fashion and a connection may see 20 or more
routers, creating significant delay, and for TCP connections,
bandwidth throttling. However, a great deal of work is underway
to (1) increase server access speeds, (2) improve backbone and
NAP bandwidth, (3) increase router speeds, and (4) introduce
ATM into the backbone for much lower latency. Futhermore, many
Internet service providers will implement proxy or cache servers
for frequently visited web pages, creating local access at least
for these pages. At the very least, xDSL will make many Internet
experiences far better than voice band modems and the resulting
market pressures will inevitably lead to capacity increases.
How does xDSL compare to cable modems?
xDSL provides a dedicated service over a single telephone line;
cable modems offer a dedicated service over a shared media.
While cable modems have greater downstream bandwidth capabilities
(up to 30 Mbps), that bandwidth is shared among all users on
a line, and will therefore vary, perhaps dramatically, as more
users in a neighborhood get online at the same time. Cable modem
upstream traffic will in many cases be slower than xDSL, either
because the particular cable modem is inherently slower, or
because of rate reductions caused by contention for upstream
bandwidth slots. The big difference between xDSL and cable modems,
however, is the number of lines available to each. There are
no more than 12 million homes passed today that can support
two-way cable modem transmissions, and while the figure also
grows steadily, it will not catch up with telephone lines for
many years. Additionally, many of the older cable networks are
not capable of offering a return channel; consequently, such
networks will need significant upgrading before they can offer
high bandwidth services.
Is DSL compatible with a Macintosh?
Yes, as long as the end user has an Ethernet 10BaseT (not coax)
interface and TCP/IP software (either MacTCP or OpenTransport,
which is included in MacOS 7.x and later). Anybody who has been
using a Mac for a dialup Internet account has TCP/IP software.
TCP/IP has been a standard part of the system software. TCP/IP
software is also available as an add-on for those end users
that do not already have it.
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