These standards are for the interoperability of the equipment between vendors. There is no technical reason that you could not have one particular speed in one direction and any other speed in the opposite direction as long as you do not exceed the total bandwidth potential of the loop. In fact, in the pre-standards days of DSL we could dial up any speed you wanted in either direction (because the DSLAM and CPE were from the same manufacturer). In this case, the standard reflects what the customer wants, not a technical limitation. If people want a different ratio of up to downlink speed it could certainly be done. ADSL is by definition asymmetric. We also sold SDSL which is symmetric service and the primary buyers were generally businesses. See G.SHDSL if you want a standard for symmetric DSL. It's there, it is just not a popular.
Steven Naslund Chicago IL >Jack, > >I don't know what manufacturer you might be thinking of, but from a standards >point of view ADSL2 and ADSL2+ both have faster upstream speeds than ADSL >(G.dmt or T1.413) > - ANSI T1.413 Issue 2 <http://en.wikipedia.org/wiki/ANSI_T1.413_Issue_2>, > up to 8 Mbit/s and 1 Mbit/s > - G.dmt <http://en.wikipedia.org/wiki/G.992.1>, ITU-T G.992.1, up to > 10 Mbit/s and 1 Mbit/s > - G.lite <http://en.wikipedia.org/wiki/G.992.2>, ITU-T G.992.2, more > noise and attenuation resistant than G.dmt, up to 1,536 kbit/s and > 512 kbit/s > - Asymmetric digital subscriber line 2 > <http://en.wikipedia.org/wiki/Asymmetric_digital_subscriber_line_2> (ADSL2), > ITU-T G.992.3, up to 12 Mbit/s and 3.5 Mbit/s > - Asymmetric digital subscriber line 2 plus > <http://en.wikipedia.org/wiki/Asymmetric_digital_subscriber_line_2_plus> >(ADSL2+), > ITU-T G.992.5, up to 24 Mbit/s and 3.5 Mbit/s
