hi tcp gurus.

i've got a weird problem with my cable setup, which i'd like to
resolve because i'd prefer to have a netbsd box as a firewall/ipnat
box than have my wife's nt box sit directly on the internet.

* working network config:
		ntbox <-> cable modem <-> cable isp <-> internet
	the ntbox can download stuff from both the cable isp's hosts and the
	internet at `high' speed (> 200k/s)

* non-working network config:
		netbsdbox <-> cable modem <-> cable isp <-> internet
	the netbsdbox downloads stuff from the internet at `high' speed,
	yet from the cable isp's servers at ~ 1 kb/s (yes, that slow!)

as you can understand, this is extremely annoying, since i need to
talk to my cable isp's servers to download email via pop for free
(as opposed to A$0.36/MB which is what they *gouge* me for everything
else)

anyone seen any similar behaviour? if not, is there any tcpdumping et
al i can do of connections to borken vs non-borken hosts that someone
can analyse to help work out why.

at avalon's suggestion i tried tweaking
	net.inet.ip.mtudisc=1		(was 0)
	net.inet.tcp.mssdflt=1400	(was 512)
but that didn't help. neither did disabling rfc1323 (which is a badly
documented option, btw).

anyone? bueller?

thanks,
luke.