V34+ MODEMS MUST USE A DTE GREATER THAN 38,400 TO ACHIEVE PEAK
PERFORMANCE
If you mostly send/receive pre-compressed files you may think
there is little need to set the DTE much higher than the DCE. But
a high-speed modems DCE link (meaning DCE-DCE) operates
synchronously whereas the DTE link (meaning DTE-DCE)operates
asynchronously. At 31,200bps DCE, the DTE transfer rate after
sync->async conversion is 39,000bps  (DCE * 10bits/char /
8bits/char). 39,000bps sounds close to 38,400bps but the results
of have the DTE even a little less than what is required are
disasterous for performance!
Here are actual results. On a V.34+ connection between USR
V.Everything Couriers. DCE 31,200 bps. Couldn't get more than about
2,665 cps (85% efficiency) (using Zmodem) transferring a 560K
zipfile if the DTE is set to 38,400 bps. Once I returned the DTE
to 57,600bps then the transfer rate returned to 3570-3600cps
(114%-115%).
I've tried these tests about six times now, checking error rates
and connect speeds before & after the transfer and the figures
have had little spread. The modems used LAPM SREJ 244/15 with
V.42bis, RTS/CTS flow control and an async data format of N81.
Cheers, Dan Bridges, Brisbug PCUG.
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 X SLMR 2.1a X 
--- Maximus/2 3.01
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