Hello, 

Thanks to all who took time to discuss TCP/IP tuning 
with me.  

A few quick tests here suggested that doubling the 
receive space might increase throughput by approximately 
three per cent.  

The default receivespace value on i386 1.6ZK was 32768.  

I did 

# sysctl -w net.inet.tcp.recvspace=65536

This change increased the download speed of my test file 
from aproximately 313 KB/sec to approximately 323 KB/sec.  

The test consisted of downloading a 39772705 byte file 
from my ISP's mirror server twice before and twice after 
the change with sysctl.  The speed measurements were 
those reported by the NetBSD ftp client.  

Increasing the receivespace to triple the original value 
had no effect that I could see.  Testing on previous 
occasions using a NetBSD machine plugged directly into 
the ISP supplied modem suggests that the router I usually 
use has no adverse effect on throughput.  

David's interesting suggestion that I try multiple 
concurrent connections resulted in values that I did not 
record but recall as something like 240 KB/sec and 150 
KB/sec -- an overall increase, but the second connection 
was much slower than the first.  Also, the aggregate 
transfer rate of 390 KB/sec remained less than two thirds 
of the 610 KB/sec capability of my "up to 5 Mbps" 
connection.  Notably, 390 KB/sec is 3.19 Mbps, just a 
bit over the "up to 3 Mbps" speed of my ISP's regular, 
non-premium connection.  

I would be grateful to hear from anybody who has additional 
comments or suggestions.  Thanks again to everyone who 
replied.  

Kindest regards, 

Tom