> tcpdump shows 0.6 - 1.0 second pauses, which looks like a timeout to 
> me. 192.168.254.130 is
> the laptop, 192.168.254.129 is the NetBSD box.

I'm not sure what is the exact environment of the tcpdump, but it shows
the sender is waiting to window update because the receiver window
is too small (702, 366, ) to send MSS (1448).  In other words, the
TCP behavior for both side looks sane.  The problem would be the
receive window of the receiver (FTP server?) looks too small to get
good performance.

> 11:26:40.402495 192.168.254.130.53311 > 192.168.254.129.62023: . 
> 2897:4345(1448) ack 0 win 33304 <nop,nop,timestamp 600652400 123> (DF) 
> [tos 0x8]
> 11:26:40.600700 192.168.254.129.62023 > 192.168.254.130.53311: . ack 
> 4345 win 702 <nop,nop,timestamp 124 600652400> (DF)
> 11:26:41.400813 192.168.254.129.62023 > 192.168.254.130.53311: . ack 
> 4345 win 2238 <nop,nop,timestamp 125 600652400> (DF)
> 11:26:41.405995 192.168.254.130.53311 > 192.168.254.129.62023: . 
> 4345:5793(1448) ack 0 win 33304 <nop,nop,timestamp 600652402 125> (DF) 
> [tos 0x8]

Atsushi Onoe