RX (download) limit problem

Hi all,

I've been digging around for over a week now and am either too slow 
to find what I need in the docs or via google, so I thought I'd stop lurking 
and see
if anyone can either help me, or slap me in the head.

I've been seeing a strange problem with my 5.4-STABLE freebsd 
firewall/router 
for about a month now and I can't for the life of me explain (or fix) it.

It can be summed up as: "any type of download seems to be limited at less 
than 
30 kB/s". I'm normally seeing around 26 kB/s and sometimes a bit higher. I'm 

connecting to a known high bandwidth public site as my performance test. 
Internal
transfers on my LAN work fine, but nothing out of the firewall (either from 
a machine
behind it or the firewall itself) can get a decent rate.

I suspect my FreeBSD config, since my linux box (when directly connected) or 
an
openBSD box are seeing transfers rates in excess of 200kB/s when fetching 
the same file.

I'm running pppoe over a 3 meg DSL loop, using ipfilter and ipnat as my 
weapons
of choice. I'm willing to try alternatives (i.e. pf), but I don't think it 
is my configurations
for ipfilter and/or ipnat that are the problems. I've tried turning them 
down to almost
nothing and haven't seen any changes at all in the limit.

The closest thing I found that describes a similar problem is:
http://freebsdaddicts.org/forum/viewtopic.php?id=575

But trying what is suggested in that thread didn't help at all.

In talking to some openBSD guys we had a theory that it might be something 
like 
the upload and download being kept symmetric and hence so low on the 
download
side. In openBSD I've seen it solved using altq's but I can't find an 
equivalent in
freeBSD without going to pf as my packet filter.

ifconfig shows:

fxp0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=8<VLAN_MTU>
inet6 fe80::202:b3ff:fe24:3797%fxp0 prefixlen 64 scopeid 0x1
ether 00:02:b3:24:37:97
media: Ethernet autoselect (10baseT/UTP)
status: active
fxp1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=8<VLAN_MTU>
inet6 fe80::202:b3ff:fe24:8182%fxp1 prefixlen 64 scopeid 0x2
inet 10.*.*.* netmask 0xff000000 broadcast 10.255.255.255<http://10.255.255.255>
ether 00:02:b3:24:81:82
media: Ethernet autoselect (10baseT/UTP)
status: active
plip0: flags=108810<POINTOPOINT,SIMPLEX,MULTICAST> mtu 1500
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
inet6 ::1 prefixlen 128
inet6 fe80::1%lo0 prefixlen 64 scopeid 0x4
inet 127.0.0.1 <http://127.0.0.1> netmask 0xff000000
tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1452
inet 66.*.*.* --> 66.*.*.* netmask 0xffffff00
Opened by PID 242

I've tried everything from forcing full-duplex media, to tweaking any any 
every
suggested tcp setting I could get at, none have an impact on the limit. I'll 
leave
those details out for now in the interest of not too long an email.

Right now I'd be happy enough with RTFM and/or someone else who at least
recognizes the problem.

Cheers,

Bruce

-- 
"Thou shalt not follow the NULL pointer, for chaos and madness await thee at 
its end"