FTP - Large file transfers (6.1)

[David Samms]

I am having repeated FTP failures while transferring a 4G file across a
LAN. Swapped out the switch, cables, and NIC's so don't believe hardware
is involved.  Have tried the default FTP server as well as vsftp and
pure-ftp with the same results.  NICs tested are em, sk, and rl. 

How to duplicate failure:  Take two 6.1 machines with a 100M lan or
x-talk cable and try to FTP a DVD image.  The transfer fails around 90%
of the time with 
	"450 Error during write to data connection" 

We have a similar problem when using samba.  The failure is not as
consistent but always occurs under heavy load.  Here is the error:

[2006/06/04 22:20:02, 0] lib/util_sock.c:write_data(557)
  write_data: write failure in writing to client 192.168.163.41. Error
Host is down

It appears, that the network connection on the server is being reset,
but why?  And where or how do I find more information?