RT>V.FC is symmetric.  First to 28k8 too.  And found in the more expensive
 
Actually VFC was developed by Hayes and Rockwell and was based on their
early preliminary suggestions for what was called V.FAST at the time.
You are correct, it was (is) symmetrical. V.FAST became V.34 after
lenghtly negociations, and it included many enhancements which were not
previously used by Rockwell and Hayes, one of which is unbalanced data
speeds for the two data channels. (Asymmetric operation).
 
RT>brand name modems.  First V34 from all brand names was symmetric
 
By all brand names you probably mean those who used the Rockwell
solution in a chipset type of modem manufacture. The inclusion, or not,
of VFC has nothing to do with whether or not a modem is expensive, it
only has to do with whether or not the manufacturer paid a royality to
Rockwell to use VFC in modems not already using Rockwell's solutions.
 
VFC was included by USR (now 3com) as a matter of compatability. USR is
also one example of a manufacturer who had prior experience with
unbalanced data channels, both full time in their HST protocols, and on
the fly as ASL, an add on the v.32bis which allowed USR modems to use
unbalanced data speeds when connected to one another via v.32bis.
Unbalanced speeds in V.34 simply take advantage of line conditions and
don't limit the better channel to the lower speed necessary for the
lesser channel if conditions warrent it.
 
--- RyPacker v2.5a
---------------