🚀 go-pugleaf

Can anyone offer me some pointers on this one please?

I am using a Linux box as an Internet gateway for a LAN and some dial-in
lines.  The box has two internal 14.4kbps modems and one external 28.8
kbps modem.  Two lines are for dialling in and on to dial out to the
ISP.

If I use one of the 14.4 kbps modems to dial the ISP I get a download
speed of around 1000-1300 bytes/sec.  I think this is pretty
reasonable.  However, when I try to use the 28.8 kbps modem to dial the
ISP (preferable) the download speed drops to between 100-200 bytes/sec!
ie, about 10 times SLOWER :-(

I think it must be the serial card, but it is a new serial card with
16550 UARTS.  I have tried configuring it at boot time with:

setserial /dev/cua1 irq 3 autoconfig
setserial /dev/cua1 irq 3 autoconfig spd_hi   and
setserial /dev/cua1 irq 3 autoconfig spd_vhi

but it is always the same.

If I ping the other end (which is quite a long way) the 14.4 modem gets
a response of around 200 msec.  The 28.8 takes anything between 1 and 5
seconds :-(  I can see the ping packets going out (via LED) but it then
takes sometimes as long as ten seconds before a burst of packets comes
back.  I started to think it might be the terminal server at the other
end, but there is no problem when the 14.4 is used.

Any other ideas?

Thanks,   Ian.