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DSL ISP Info
A brief history about DSL and it's development.
DSL Service
Providers
Some top DSL providers and plans they offer to consumers.
What Is DSL
An introduction to the technology and driving force behind it.
How It Works
Learn how DSL works and related hardware that make the technology
possible.
Types of DSL
ADSL, SDSL, SHDSL, IDSL and more ...
Advantages And Disadvantages
Look at some of the principal advantages and disadvantages of the DSL.
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Type Of DSL
Unlike dial up, DSL comes
in many flavors. Principally we have:
ADSL
Asymmetric digital subscriber line (ADSL) is the popular of all the DSL
types. Several homes and small businesses find ADSL easy to use.
ADSL provides high speed transmission of information at a high bandwidth
over regular phone lines. Unlike dialup phone, ADSL gives consumers
permanent internet connectivity. ADSL can contain both analog and digital
information on the same telephone line. ADSL is said to be asymmetric
because most of the bandwidth is used to transmit information downstream.
You can have speeds up to 8 Megabits per second which translates into over
100 times faster the speed of regular dial up. Upstream speed can be up to
640 Kbps.
ADSL uses dedicated bandwidth so multiple connections to several home will
not affect its performance or speed. Rather, your speed will depend on how
far you are from the DSL provider.
SDSL
Symmetric digital subscriber line (SDSL) is best suited for delivering
symmetric connectivity to users. SDSL also uses the regular telephone lines
but can offer several services along the same line. With SDSL, you can have
a private line, digital voice transmission, and Internet Protocol (IP), or
frame relay on the same line. Due to its symmetric nature, it provides a
consistent upload and download transmission speeds. The rate of receiving
data is the same as sending. SDSL can offer speeds up to 2.3 mbps; making
them a popular option for people who deal with teleconferencing and
uploading of heavy materials such as multimedia to remote servers.
SHDSL
Symmetric high-speed DSL (SHDSL) is another version of SDSL, which attempts
to improve on both HDSL and SDSL by only requiring a single line and by
integrating low-level services of interest to small businesses. As the
latest development in DSL technology, SHDSL delivers standards-based,
high-speed, symmetric DSL over a single copper pair. SHDSL is based on the
G.shdsl standard established by the International Telecommunication Union -
Telecommunication Standardization Sector (ITU-T). G.shdsl is a version of
symmetrical rate adaptive DSL that can accommodate line rates from 192
kilobits per second (kbps) to 2.3 megabits per second (Mbps).
As with SDSL, SHDSL is symmetric. This allows for a maximum data rate that
is the same both upstream and downstream. Typically, SHDSL generates speeds
of 2.3 Mbps upstream and downstream.
SHDSL addresses rate/range adaptability, spectral compatibility, impairment
tolerance, and high-speed symmetrical deployment for applications such as
multiple voice-line delivery, internet access and remote LAN access. SHDSL
gives providers a platform to deliver improved services at a much lower cost
than traditional T1/E1 - with the flexibility to satisfy a variety of
service needs and generate increased revenue. SHDSL offers the benefits of
T1/E1 and can be used in the same bundled cable loop as ADSL, without
causing interference. Business customers need the high speed of T1/E1
transmission, leased line services, and guaranteed performance for high
bandwidth applications such as voice, video, and data.
IDSL
IDSL is another variation of technology which permits users to use regular
ISDN card technology for transmission of only data.
IDSL was created for users who are located farther fro the DSL companies so
that they can take advantage of the popular asymmetric DSL which can offer
data speeds of up to 144 kbps.
In operation, IDSL uses digital transmissions to bypass the company’s CO
equipment that carries analog signals. It uses the regular ISDN data coding
to lump up an ISDN service and voice signals onto one line.
HDSL-2
High bit rate digital subscriber line (HDSL-2) is a more recent type of DSL.
It was created to replace T1pE1 lines and the earlier HDSL technology.
HDSL-2 can transmit data up to speeds of 1.5 Megabits per second (Mbps)
across a single pair of copper wires and covers distances of up to 12,000
feet.
HDSL-2 supports interoperability; meaning different vendors can interconnect
each other without problems of software or hardware incompatibility. HDSL-2
also supports voice, data, video using asynchronous transfer mode (ATM),
private-line T1 service and frame relay.
Recently there has been the release of G.SHDSL, a multiple-rate version
recommended b the International Telecommunication Union (ITU). G.SHDSL is a
standard symmetric rate DSL capable of delivering speeds up to 2.3 Mbps.
VDSL
Very high bit rate digital subscriber line (VDSL) is one of the newest
developments in DSL.
VDSL delivers fast data rates across short distances - the shorter the
distance, the faster the connectivity. VDSL can produce speeds up to 55
Megabits per second (Mbps) over a distance of 1,000 feet.
VDSL connects to neighborhood optical network units (ONUs), which then
extends connectivity to the telephone company's central office (CO) main
fiber network backbone. Thus, users on this service can obtain the highest
bandwidth any phone line can offer.
Experimentation has proved that DSL can deliver interactive video, video o
demand and high definition TV.
G.Lite
G.Lite bears similarity to ADSL. It offers low speed data transfer by
eliminating the need for POTS splitters at the customers end. G.Lite is easy
to install and chap but have a lower rate of 1.5 mbps downstream and 384kbps
upstream.
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