New
Technology
New
Way to Internet
DSL,
or Digital Subscriber Line, 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 offering
exciting new interactive multimedia applications including
multi-player gaming, video-on-demand and video catalogs.
DSL
enables two general types of applications -- interactive
video and high-speed data communications. Interactive video
includes movies-on-demand, and other video-on-demand
applications such as delayed TV segments, video games, video
catalogs, and video information retrieval. Data
communication includes 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 lines, compared
to new cabling which has reached comparatively few homes and
virtually no small businesses.
DSL
vs. ISDN
These
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.
DSL
vs. Cable Modem
In
San Mateo, California, on May 17, 1999
¡V Keynote Systems, the recognized authority on Internet
performance, announced that DSL outperformed a cable modem
during peak-usage evening hours in a month-long benchmark
test of over 150,000 web-page downloads from 40 popular web
sites. The test results showed that World Wide Web pages
downloaded much slower over cable modems than over T-1
connections and that cable-modem performance deteriorated
during evening hours when peak residential use of the
Internet occurs. Keynote conducted the tests in the San
Francisco Bay area throughout April over an asymmetric DSL
connection (128/384 kbps) to SBC¡¦s Pacific Bell network,
over a cable modem connected to the At Home network through
a cable system operated by AT&T¡¦s TCI unit, and over
T-1 connections supplied by AboveNet Communications, Exodus
Communications, Intermedia Communications¡¦ DIGEX unit and
Savvis Communications.
The
median download time over DSL for the 40 web pages was 3.55
seconds in April during the hours of 5 p.m. to 11 p.m.
Pacific time which are peak personal-use hours according to
Nielsen/NetRatings. This result was nearly 11 percent faster
than the median of 3.97 seconds over cable modem during the
same period. Although cable modems outperformed DSL during
business hours with a 3.68-second performance versus DSL¡¦s
4.30 seconds, cable-modem performance degraded by 8 percent
during the evening hours while DSL performance improved 17
percent. Keynote also conducted the same performance
measurements over four different T-1 connections, which
performed 36 to 48 percent faster than DSL or cable modem. |