>>check your -rtscts. and the cable and the at& command that deals with it,
>
>I am forcing a slow connection rate via the at&n command to be sure it's
>not the DA/AD conversion that is dropping data.
It happened here with an ISDN connection between an ISDN card and an
ISDN modem (with built in sync-async conversion). Kernel versions were
2.2.12 and AFAIK 2.2.5.
Judging from the LEDs on the modem the transfer rate constantly
increased until it reached a certain point, then it collapsed. After
1-2 seconds it resumed at a very slow rate and then started to speed up
until next collapse. The result was about 1kByte/s.
ifconfig didn't show any overruns, 'cat /proc/tty/driver/serial' didn't
either. 'echo "0" > /proc/sys/net/ipv4/tcp_timestamps' made things
better (4kBytes/s).
With 2.3.20 things speed up to >6.5kB/s (echo 1 > tcp_timestamps). And
even bidirectional ftp transfer is now about 5 kB/s for each direction.
2.2.12 did hardly do any bidirectional transfers (except for ping with
big packetsizes).
Peter
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