What Is ADSL?

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What Is ADSL

ADSL, or Asymmetric Digital Subscriber Line, is an asymmetric of DSL. The speed of this technology for use over existing mediums (phone lines) is astounding: up to 8,448Mbps to the customer and up to 800Kbps to the ‘’network ‘’.

A basic ADSL overall downstream rate depends on, among other things, the distance covered, the size the size of the wire, and interference. Upstream speeds range from 16Kbps. Table 2give the standard downstream speeds at certain distances.

ADSL speed/distance.

Speed (feet)

Distance (Mbps)

<=9000

8.448

>9000 to <=12000

6.312

>9000 to <=12000

2.048

<16000 to <=18000

1.544

ADSL was designed for two major functions:

high speed data communications and interactive video. Data communication functions can be Internet access, corporate telecommuting, or other specialized network applications. Interactive video covers things such as video on demand, movies, games, or any other application that requires high- speed network video. Presently, ADSL only supports interfaces to T-1/E-1; Future enhancements are planned for ADSL to the desktop.

The biggest strength in ADSL lies the fact that it uses existing telephone line over which to communicate.  This means that more than 700 million (existing) phone customers are already cabled for ADSL and require little or no upgrade. Technologies such as ISDN or cable modems can require expensive hardware and software upgrades in both the network and in the client site. But, ADSL is still in testing around most of the world, with anticipated niche release slated for late 1997. This release will be available mainly for Internet access and other packet- based communication applications.

ADSL average, minimum, and maximum speed.

Channel Average Minimum Maximum
High-speed downstream 6Mbps 1.5Mbps 9Mbps
Medium-speed duplex 64Kbps 16Kbps 640Kbps

Gigabit Ethernet (100Mbps??)

Current Ethernet network are available in either 10Mbps or 100Mbps size.  Gigabit network increases that bandwidth tenfold, allowing speeds of up to 100Mbpss. Existing Ethernet and Fast Ethernet network are 100% compatible and easily upgradable to the new gigabit network architecture. This new supports the CSMA/CD protocol and will be available on fiber, coaxial cable, and even UTP.

ATM

ATM, or Asynchronous Transfer Mode, is the proposed communication standard for broadband ISDN.ATM is a very high performance solution for both local area networks. ATM makes use of a special high-speed switch that connects to computers by optical fibers (1 for send and 1 for receive).ATM also supports simultaneous transmission of voice, data, and video one network technology. It is currently available at a speed of 25Mbps, but was originally designed to run at 155Mbps. Future expansion could be in the gigabit or even terabit range.

SONET

The other major standard that will affect digital service in the near future is the Synchronous Optical Network (SONET). SONET uses a new standard for framing that allows massive aggregative of DSO channels. As shown in table 16.3, SONET is designed to provide bandwidth capacity in the gigabit range. While the technology is currently used only by the telecommunication companies, you can imagine that the service will follow the example set by T-1 and T-3 lines, and eventually become a public service for large companies.

The SONET Hierarchy:

SONET Level Maximum Bandwidth

OC1

51.84Mbps

OC3

155.52Mbps

OC9

466.56Mbps

OC12

622.08Mbps

 

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