🚀 go-pugleaf

Greetings!

I have 3 semi-problems with a linux machine using an external TA. Can anyone
help?

No.1: the TA will only connect reliably upto 57600. At 115200, virtually
nothing comes in or goes out. 90% of full speed on an ISDN is better than
nothing, but where's the extra 10% gone?

No.2: kppp load indicates that /roughly/ every 40-60kb (depending on
mru/mtu) of download traffic drops off for a short while (upto around 4
seconds), then resumes at the original speed. This happens even at 9600, and
looks for all the world as if X amount of data is being cached, then
flushed, then the next X is called for. Whats causing this?

Observations: The TA is a BT ignition external model (ala Motorola Bitsurfr)
connected to a regular ISDN 2e line. The TA, when plugged into a windows box
will happily reach 64kbps. As a test, I can show that a given 6.5mb file
will consistently download in around 90 seconds from ftp.demon.co.uk whereas
the it'll take around 120 seconds and up on the linux machine. This despite
that the sdu account logged into being the same, serial cable is the same,
etc etc. Ergo, something must be wrong either with the hardware linux is
running on, or I've badly configured linux.

Machine is t500 from Dell. Linux dist. is redhat6.1 using kernel 2.2.12-20
(2.2.14 exhibits identical (mis)behaviour). Setserial is using defaults:
spd_normal and baud_base 115200. Dialup is via a pppd script based on that
held at http://www.cix.co.uk/~dunnp/connecting.html. Little change is seen
when mru and mtu were tried at alternate levels 296, 542, 976 and 1200.

Thanks for any indications what's happening, or wherelese I might look,
--
Alistair Mann