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Note: This section is out of date and no longer maintained.
It is retained for the value of any residual information contained in it. DSL - Section 3More detail.. DSL[2] (Digital Subscriber Line) is a generic name for a family of standards allowing high speed data transfer over telephone lines (POTS), otherwise known as twisted pair. For carrying IP, DSL competes with cable modems, satellite digital data feeds, wireless digital data, ISDN, 56k modems and more expensive frame-relay lines etc.
Since the twisted pair lines used in the telephone network that are to carry DSL are not shielded from interference, there are limits on the distance DSL signals can travel before degrading the maximum DSL speeds available in all DSL standards.
This distance limitation of DSL is only one of many potential technical hurdles to pass before an installation is complete.
..take me back ---- tell me more...
maximum DSL speedsMaximum DSL speed is a function of distance, the gauge (thinness) of the phone wire used in your locale, and the DSL technology employed.
The fastest DSL now commonly available is ADSL, and it offers maximum download speeds of up to 7.1mbps and around 1.1m upload. Most residential ADSL is limited to 90-680k for download, depending on the Telco. SDSL currently has a max of 1.5mbps, but that is both up and down (symmetric). Other common rates are (in k bits per second) 640k/90k, 1600k/90k, 680k/680k for ADSL.
Rule of thumb for converting speeds to something easier to understand: take the k bps, and divide by 10. This is the maximum transfer K per second you are ever likely to see in a browser download window. More accurately, divide by 8 and take off 13%, which is overhead from tcp/ip and, more importantly, ATM overhead. (DSL lines use ATM as an underlying data-transport protocol).
Modems range from 2-5k a second, DSL lines from 10-500k a second, office computer interconnections are usually either (best case) 800k a second (10mbit) or 8000k a second (100mbit switched).
A 30mb game demo download would therefore take at best, 1 minute on the fastest ADSL, 30 seconds on an office or home network, and 3 seconds on a clean switched net with top components, to download (transfer) between devices.. On a 56k modem, assuming no line drops, it would take around.. um.. er.. 2-3 hours to transfer, and thats if the modem connection doesn't drop out half way through!
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