In article <005b01c0bf47$85c976d0$0300a8c0@ERIC6D66J07ZKZ> you write:
>There are some programs under Windows to tune TCP/IP parameters like MTU,
>MSS, RWIN, TTL, depending of your internet connection (cable, ADSL, modem).
>Is there a similar thing under NetBSD ? Maybe with sysctl interface ?

Some obvious sysctl variables under net.inet:

net.inet.ip.ttl = 64
net.inet.tcp.recvspace = 16384
net.inet.tcp.mssdflt = 512

The MTU is set on a per-interface basis with ifconfig <if> mtu <mtu>.

-- 
Ben Harris                                                   <bjh21@netbsd.org>
Portmaster, NetBSD/arm26               <URL:http://www.netbsd.org/Ports/arm26/>